U.S. patent application number 16/604756 was filed with the patent office on 2020-12-03 for photo-voltaic element and method of manufacturing the same.
This patent application is currently assigned to Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO. The applicant listed for this patent is Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO. Invention is credited to Hieronymus Antonius Josephus Maria ANDRIESSEN, Maarten Sander DORENKAMPER, Herbert LIFKA, Huibert Johan VAN DEN HEUVEL, Siegfried Christiaan VEENSTRA.
Application Number | 20200381568 16/604756 |
Document ID | / |
Family ID | 1000005048920 |
Filed Date | 2020-12-03 |
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United States Patent
Application |
20200381568 |
Kind Code |
A1 |
LIFKA; Herbert ; et
al. |
December 3, 2020 |
PHOTO-VOLTAIC ELEMENT AND METHOD OF MANUFACTURING THE SAME
Abstract
A photo-voltaic element (1) comprising a stack of layers is
provided. The stack of layers at least includes the following
layers arranged in the order named: a first electrode layer, a
first charge carrier transport layer, an insulating layer, a second
electrode layer, a second charge carrier transport layer, and a
photo-electric conversion layer. The photo-electric conversion
layer (70), comprises a plurality of distributed extensions (72)
extending through the second charge carrier transport layer (60),
the second electrode layer (50) and the insulating layer (40) to
the first charge carrier transport layer (30). The extensions (72)
have an effective cross-section D.sub.eff in the range of 0.5 to 10
micron, and have an average pitch in the range of 1.1 to 5 times
said effective cross-section.
Inventors: |
LIFKA; Herbert; (Eindhoven,
NL) ; VEENSTRA; Siegfried Christiaan; (Heeze, NL)
; DORENKAMPER; Maarten Sander; (Rosmalen, NL) ;
ANDRIESSEN; Hieronymus Antonius Josephus Maria; (Beerse,
BE) ; VAN DEN HEUVEL; Huibert Johan; (Eindhoven,
NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nederlandse Organisatie voor toegepast-natuurwetenschappelijk
onderzoek TNO |
's-Gravenhage |
|
NL |
|
|
Assignee: |
Nederlandse Organisatie voor
toegepast-natuurwetenschappelijk onderzoek TNO
's-Gravenhage
NL
|
Family ID: |
1000005048920 |
Appl. No.: |
16/604756 |
Filed: |
April 12, 2018 |
PCT Filed: |
April 12, 2018 |
PCT NO: |
PCT/NL2018/050224 |
371 Date: |
October 11, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 31/022425 20130101;
H01L 31/035281 20130101; H01L 31/0749 20130101; H01L 31/186
20130101 |
International
Class: |
H01L 31/0224 20060101
H01L031/0224; H01L 31/18 20060101 H01L031/18; H01L 31/0352 20060101
H01L031/0352; H01L 31/0749 20060101 H01L031/0749 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 13, 2017 |
EP |
17166454.3 |
Claims
1. A photo-voltaic element comprising a stack of layers, the stack
of layers at least including the following layers arranged in the
order named: a first electrode layer for receiving charge carriers
of a first polarity, a first charge carrier transport layer, for
transport of charge carriers having said first polarity, an
insulating layer, a second electrode layer for receiving charge
carriers of a second polarity opposite to said first polarity, a
second charge carrier transport layer, for transport of charge
carriers having said second polarity, a photo-electric conversion
layer, wherein charge carriers of the first polarity have a first
mobility and wherein charge carriers of the second polarity have a
second mobility, the photo-electric conversion layer comprising a
plurality of distributed extensions extending through said second
charge carrier transport layer, said second electrode layer and
said insulating layer to the first charge carrier transport layer,
the extensions having an effective cross-section D.sub.eff in the
range of 0.5 to 10 micron, and having an average pitch in the range
of 1.1 to 5 times said effective cross-section, the effective
cross-section being a diameter of a circle having an area
corresponding to the cross-sectional area A.sub.O of the
extensions, and the extensions having a circumference O that is
less than 10 times the effective diameter D.sub.eff, a
contact-surface of the photo-electric conversion layer with the
first charge carrier transport layer having a first surface area,
and a contact-surface of the photo-electric conversion layer with
the second charge carrier transport layer having a second surface
area, a ratio between the second surface area and the first surface
area being approximately equal to a ratio between the first
mobility and the second mobility.
2. The photo-voltaic element according to claim 1, wherein said
second electrode layer has anodized edge surfaces facing the
extensions of the photo-electric conversion layer.
3. The photo-voltaic element according to claim 1, wherein an
insulating material is provided around said extensions, forming an
insulating wall between said second electrode layer and said
photo-electric conversion layer.
4. The photo-voltaic element according to claim 1, further
comprising a growth layer at an interface between said
photo-electric conversion layer and said second charge carrier
transport layer as well as at an interface between said extensions
of the photo-electric conversion layer and each of edge surfaces of
said second charge carrier transport layer, said second electrode
layer and said insulating layer and at an interface between said
extensions of the photo-electric conversion layer and the first
charge carrier transport layer.
5. The photo-voltaic element according to claim 1, wherein the
photo-electric conversion layer is provided of a perovskite
material.
6. The photo-voltaic element according to claim 1, wherein the
photo-electric conversion layer is made of copper indium gallium
selenide (CIGS).
7. The photo-voltaic element according to claim 1, wherein an edge
portion of an upper surface of the first electrode layer is kept
free from material of the first charge carrier transport layer and
is provided with a first electrical contact and or an edge portion
of an upper surface of the second electrode layer is kept free from
material of the second charge carrier transport layer and is
provided with a second electrical contact.
8. The photo-voltaic element according to claim 1, wherein said
first electrode layer, said first charge carrier transport layer,
said insulating layer and said second electrode layer are provided
as a plurality of layer segments, wherein a plurality of lateral
sub-stack segments each comprise a respective first electrode layer
segment, a first charge carrier transport layer segment, an
insulating layer segment and a second electrode layer segment,
wherein a second electrode layer segment of a lateral sub-stack
segment extends over a first electrode layer segment n a
neighboring sub-stack segment, therewith forming an electrical
connection between said second electrode layer segment of said
lateral sub-stack segment and said first electrode layer segment in
said neighboring lateral sub-stack segment.
9. The photo-voltaic element according to claim 1, wherein the
extensions taper outward in a direction from the first charge
carrier transport layer towards the second charge carrier
layer.
10. The photo-voltaic element according to claim 9, wherein a
material of the second charge carrier transport layer covers a
surface of the second electrode surrounding the extensions.
11. The photo-electric element according to claim 1, wherein the
first charge carrier layer is absent in areas of the first
electrode layer covered by the insulating layer.
12. Method of manufacturing a photo-voltaic element comprising the
steps of: providing a substrate; depositing thereon a stack of
layers comprising at least in the order named: a first electrode
layer for receiving charge carriers of a first polarity; a first
charge carrier transport layer, for transport of charge carriers
having said first polarity; an insulating layer; a second charge
carrier transport layer, for transport of charge carriers having a
second polarity opposite to said first polarity; a second electrode
layer for receiving charge carriers of the second polarity; wherein
the insulating layer and layers subsequently deposited in this step
form a substack having an upper surface, applying a resist layer on
said upper surface, wherein said resist layer is provided with a
plurality of distributed openings towards said upper surface, the
openings having an effective cross-section D in the range of 0.5 to
10 micron, and having an average pitch in the range of 1.1 to 5
times said effective cross-section, the effective cross-section
being a diameter of a circle having an area corresponding to the
cross-sectional area A.sub.O of the extensions, and the extensions
having a circumference O that is less than 10 times the effective
diameter D.sub.eff, etching to selectively remove material of the
sub-stack facing the openings, removing the resist layer subsequent
to said etching, depositing and curing a photo-electric conversion
layer subsequent to said removing wherein a contact-surface of the
photo-electric conversion layer with the first charge carrier
transport layer has a first surface area, and a contact-surface of
the photo-electric conversion layer with the second charge carrier
transport layer has a second surface area, and a ratio between the
second surface area and the first surface area is approximately
equal to a ratio between a first mobility of the charge carriers
having said first polarity and a second mobility of the charge
carriers having said second polarity.
13-14. (canceled)
15. The method according to claim 12, wherein the second charge
carrier transport layer is deposited with an electroplating process
and subsequent to removing the resist layer, and preceding
depositing and curing a photo-electric conversion layer.
16. The method according to claim 12, wherein the first charge
carrier transport layer is deposited with an electroplating
process.
17. The method according to claim 12, further comprising anodizing
an edge surface of the second electrode layer resulting from said
etching, said anodizing being performed prior to the step of
depositing the photo-electric conversion layer.
18. The method according to claim 12, further comprising
conformally depositing a layer of an insulating material subsequent
to said step of etching and anisotropically etching said layer to
removes the insulating material from the surface of the second
charge carrier transport layer and from the surface portions of the
first charge carrier transport layer within the openings while
keeping a layer of the insulating material on the walls of the
openings intact.
19. The method according to claim 12, further comprising depositing
a growth layer subsequent to said step of etching and prior to the
step of depositing the photo-electric conversion layer.
20. The method according to claim 12, further comprising depositing
a barrier over said photo-electric conversion layer.
21. (canceled)
22. The method according to claim 20, comprising applying a light
in coupling structure over said barrier.
23. (canceled)
24. The method according to claim 12, wherein the photo-electric
conversion layer is provided of a perovskite material or of copper
indium gallium selenide (CIGS).
Description
BACKGROUND OF THE INVENTION
Field of the invention
[0001] The present invention pertains to a photo-voltaic element.
The present invention further pertains to a method of manufacturing
the same.
Related Art
[0002] A photo-voltaic element is disclosed in CN105140398 that
comprises a conductive substrate; a uniform electron transport
layer; a dielectric layer; a metal layer; and a perovskite layer as
a photo-electric conversion layer. The latter has a plurality of
channels through the dielectric layer and the metal layer that
contact the electron transport layer. Accordingly the perovskite
photo-electric conversion layer has its electric contacts for
delivering electrical energy at the same side. Therewith it can be
avoided that light to be converted has to pass through an electrode
layer, as a result of which it would be attenuated before
conversion.
[0003] The cited document also presents a method of manufacturing
the photo-voltaic element disclosed therein. Therein a substrate is
provided of a transparent conductive glass and an electron
transport layer is deposited thereon by magnetron sputtering ZnO.
Subsequently a layer of dispersed PS pellets having an original
diameter of 2 um is deposited resulting in a hexagonal close-packed
structure of said PS pellets. The PS ball diameter is subsequently
reduced to 1 um by dry etching using RIE. A dielectric layer of
Al2O3 is deposited thereon using ALD deposition followed by
magneton sputtering of an Au layer. Subsequently, using a solvent
and an ultrasonic treatment the PS pellets and the portions of the
Al2O3 layer and the Au layer deposited thereon are removed, so that
an Au mesh is obtained that is insulated from the electron
transport layer. A perovskite layer is spin coated thereon that
both contacts the Au mesh and the ZnO electron transport layer.
[0004] It is a disadvantage of this known process, a lift-off
process, that the patterning process is not well controlled. As a
result the boundaries of the openings in the insulator layer and
the upper electrode layer are jagged and an unreliable or even
non-working product is obtained.
[0005] It is noted that WO2017/060700, published after the priority
date of this document also uses a lift-off process. As shown for
example in FIG. 2, subsequently:
[0006] the patterned resist layer is formed on the lower electrode
(a)
[0007] the insulator and HCE layer are deposited thereon (b)
[0008] the patterned resist layer and the portions of the insulator
layer and HCE layer present thereon are removed in the lift-off
step (c).
SUMMARY OF THE INVENTION
[0009] It is a first object of the invention to provide a
photo-voltaic element with an improved conversion efficiency.
[0010] It is a second object of the invention to provide a method
of manufacturing this improved photo-voltaic element.
[0011] In accordance with said first object, according to a first
aspect, a photo-voltaic element is provided as claimed in claim
1.
[0012] In accordance with said second object, according to a second
aspect, a method of manufacturing a photo-voltaic element is
provided as claimed in claim 8.
[0013] The photo-voltaic element is provided as claimed in claim 1
comprises a stack of layers that at least include in the order
named: a first electrode layer, a first charge carrier transport
layer, an insulating layer, a second electrode layer, an second
charge carrier transport layer, and a photo-electric conversion
layer.
[0014] The first electrode layer is provided for receiving charge
carriers of a first polarity, for example electrons, or
alternatively for receiving holes as the charge carrier. The first
charge carrier transport layer is provided for transport of charge
carriers having the first polarity. E.g. if the first electrode
layer is a cathode provided for receiving electrons as the charge
carrier then the first charge carrier transport layer is an
electron transport layer. Alternatively, if the first electrode
layer is an anode provided for receiving holes as the charge
carrier then the first charge carrier transport layer is a hole
transport layer. The insulating layer may be provided of any
sufficiently insulating organic or inorganic material. The second
electrode layer is provided for receiving charge carriers of a
second polarity opposite to the first polarity. Hence if the first
electrode layer is a cathode then the second electrode layer is an
anode and vice versa. The second charge carrier transport layer is
provided for transport of charge carriers having the second
polarity. Accordingly the second charge carrier transport layer is
a hole transport layer if the second electrode layer is an anode
and an electron transport layer if the second electrode layer is a
cathode. The photo-electric conversion layer comprises a plurality
of distributed extensions that extend through the second charge
carrier transport layer, the second electrode layer and the
insulating layer to the first charge carrier transport layer.
[0015] Because the photo-electric conversion layer is the uppermost
layer of the stack (apart from e.g. a protection layer or
encapsulation), it is not necessary that the various layers are
transparent. Therewith one or more of the electrodes may be formed
as a metal layer, for example an aluminum or a copper layer,
possibly sandwiched between intermediate layers, e.g. as MoAlMo or
CrCUCr. Nevertheless, embodiments may be contemplated wherein a
transparent electrically conductive material is used for the
electrodes, for example a transparent electrically conductive oxide
like ITO. This is advantageous in that the device so obtained is
bilaterally sensitive. Alternatively, this may be combined with a
substrate having a reflecting surface. In this embodiment, light
entering the device that is not converted in the photo-electric
conversion layer is reflected back to the latter, so that it can
still be (partially) converted.
[0016] Therewith the photo-electric conversion layer is
electrically coupled to both the first charge carrier transport
layer and the second charge carrier transport layer. In this
arrangement solar radiation R does not need to traverse an
electrode layer or a charge carrier transport layer, which
contributes to an efficient operation of the photo-voltaic
element.
[0017] An optimal conversion efficiency is achieved by the presence
of a charge carrier transport layer between the first electrode
layer and the photo-electric conversion layer as well as between
the second electrode layer and the photo-electric conversion
layer.
[0018] The extensions have an effective cross-section D.sub.eff in
the range of 0.5 to 10 micron, and have an average pitch in the
range of 1.1 to 5 times their effective cross-section. The
effective cross-section is defined here as the diameter of a circle
having an area corresponding to the cross-sectional area A.sub.O of
the extensions.
I . e . D eff = 4 A .PHI. .pi. ##EQU00001##
[0019] The extensions are typically cylindrical. Alternatively the
extensions may taper inward or outward. The extensions may have any
cross-section, such as circular, square or triangular. The
circumference O of the extensions is less than 10 times the
effective diameter D.sub.eff and preferably less than 5 times the
effective diameter D.sub.eff. Therewith an optimum contact surface
between the photo-electric conversion layer and the first charge
carrier transport layer is achieved with minimum disruption of the
intermediary layers, in particular the second electrode layer and
the second charge carrier transport layer.
[0020] In an embodiment of the photo-voltaic element the extensions
taper outward in a direction from the first charge carrier
transport layer to the second charge carrier layer.
[0021] In an embodiment thereof, material of the second charge
carrier transport layer covers a surface of the second electrode
surrounding the extensions. Therewith a contact surface provided
for the photovoltaic layer is improved.
[0022] In an embodiment, the first charge carrier layer is absent
in areas of the first electrode layer covered by the insulating
layer. Also in this case, the stack formed in the product is deemed
to comprise first charge carrier layer and a subsequent insulating
layer, as the surface of the insulating layer will be above a
surface of the first charge carrier layer, when traversing the
layers starting from the substrate on which the layers are
deposited.
[0023] In an embodiment the photo-electric conversion layer is
provided of a perovskite material. Perovskite materials typical
have a crystal structure of ABX.sub.3, wherein A is an organic
cation as methylammonium (CH.sub.3NH.sub.3).sup.+, B is an
inorganic cation, usually lead (II) (Pb.sup.2+), and X is a halogen
atom such as iodine (I.sup.-), chlorine (Cl.sup.-) or bromine
(Br.sup.-). Perovskite materials are particularly advantageous in
that they can be processed relatively easily and in that their
bandgap can be set to a desired value by a proper choice of the
halide content. A typical example is methylammonium lead trihalide
(CH.sub.3NH.sub.3PbX.sub.3), with an optical bandgap between 1.5
and 2.3 eV depending on halide content. Another more complex
structure example is Cesium-formamiclinum lead trihalide
(Cs.sub.0.05(H.sub.2NCHNH.sub.2).sub.0.95PbI.sub.2.85Br.sub.0.15)
having a bandgap between 1.5 and 2.2 eV. Other metals such as tin
may replace the role of Pb in perovskite materials. An example
thereof is CH.sub.3NH.sub.3SnI.sub.3. Also combinations of Sn with
Pb perovskites having a wider bandgap in the range of 1.2 to 2.2 eV
are possible. In another embodiment the photo-electric conversion
layer is made of copper indium gallium selenide (CIGS).
[0024] The geometry of the substantially circular cylindrical
extensions with an effective cross-section D.sub.eff in the range
of 0.5 to 10 micron, and with an average pitch in the range of 1.1
to 5 times their effective cross-section makes it possible to
optimally tune the contact-surface of the photo-voltaic layer with
the first and the second charge carrier transport layer
respectively dependent on the type of perovskite material used for
the photo-voltaic layer. This is favorable, in that the ratio of
mobility for holes and electrons may differ. E.g. if for a certain
perovskite the mobility of electrons is 3 time higher than for
holes, the surface area of the HTL preferably is approximately
3.times. the surface area of the ETL for an optimal efficiency.
[0025] The method as claimed in claim 13 enables manufacturing the
photo-voltaic element of claim 1. The claimed method comprises the
steps of:
[0026] providing a substrate;
[0027] depositing thereon a stack of layers comprising at least in
the order named: [0028] a first electrode layer for receiving
charge carriers of a first polarity; [0029] an insulating layer;
[0030] a second electrode layer for receiving charge carriers of a
second polarity opposite to said first polarity; wherein the
insulating layer and layers subsequently deposited in this step
form a sub-stack having an upper surface,
[0031] applying a resist layer on said upper surface, wherein said
resist layer is provided with a plurality of distributed openings
towards said upper surface, the openings having an effective
cross-section D in the range of 0.5 to 10 micron, and having an
average pitch in the range of 1.1 to 5 times said effective
cross-section,
[0032] etching to selectively remove material of the sub-stack
facing the openings,
[0033] removing the resist layer subsequent to said etching,
[0034] depositing and curing a photo-electric conversion layer
subsequent to said removing.
[0035] The method further comprises depositing a first charge
carrier transport layer for transport of charge carriers having the
first polarity and depositing a second charge carrier transport
layer for transport of charge carriers having said second
polarity.
[0036] In an embodiment depositing the first charge carrier
transport layer is subsequent to depositing the first electrode
layer and preceding to depositing the insulating layer and said
depositing the second charge carrier layer is subsequent to
depositing the insulating layer and preceding depositing the resist
layer.
[0037] In an embodiment, of the method the second charge carrier
transport layer is deposited with an electroplating process and
subsequent to removing the resist layer, and preceding depositing
and curing a photo-electric conversion layer.
[0038] In an embodiment the first charge carrier transport layer is
deposited with an electroplating process subsequent to removing the
resist layer, and preceding depositing the second charge carrier
layer.
[0039] The method according to the present invention enables the
deposition of a thicker stack of layers on the first charge carrier
transport layer than would be possible when using the pellet based
approach known from the prior art. In this way the second charge
carrier transport layer can be provided, therewith significantly
improving efficiency of the photo-voltaic element.
[0040] Various methods may be used for depositing and applying
layers. These methods may include spin-coating, printing methods,
slot-die coating and vapor deposition methods like physical vapor
deposition (e.g. E-beam PVD, Sputter PVD), (spatial) Atomic Layer
Deposition ((s)ALD), and chemical vapor deposition (e.g.
plasma-enhanced chemical vapor deposition (PECVD)).
[0041] Etching processes may be applied to remove a material (or a
part of the material) from a surface either by a chemical reaction
generated by the use of a reactive mix of gases (plasma-etching) or
by submerging the substrates in a reactive solution where the layer
is removed by dissolution or chemical reaction (wet-etching).
[0042] A selective etching is made possible by using a mask that
locally protects the underlying layer(s). A patterning in such a
mask may be obtained for example by optical lithography wherein
light is used to transfer a geometric pattern from a photo-mask to
a light sensitive chemical photoresist on the substrate. Also
imprinting can be applied to pattern the mask. Alternatively the
mask may be directly applied in the desired pattern, for example by
printing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] These and other aspects are described in more detail with
reference to the drawing. Therein:
[0044] FIG. 1A schematically shows a top-view of a semi-finished
product obtained during performing a method according to the second
aspect,
[0045] FIG. 1B shows a cross-section according to IB-IB in FIG.
1A,
[0046] FIG. 2A shows a top-view corresponding to the area IIA of a
semi-finished product obtained after an additional manufacturing
step of a method according to the second aspect,
[0047] FIG. 2B shows a cross-section according to IIB-IIB in FIG.
2A,
[0048] FIG. 3A shows a top-view corresponding to the area IIA of a
semi-finished product obtained after a further additional
manufacturing step of a method according to the second aspect,
[0049] FIG. 3B shows a cross-section according to IIIB-IIIB in FIG.
3A,
[0050] FIG. 4A shows a top-view corresponding to the area IIA of a
semi-finished product obtained after a still further additional
manufacturing step of a method according to the second aspect,
[0051] FIG. 4B shows a cross-section according to IVB-IVB in FIG.
4A,
[0052] FIG. 4C shows in the same cross-section an optional
manufacturing step of a method according to the second aspect,
[0053] FIG. 4D shows in the same cross-section an alternative
optional manufacturing step of a method according to the second
aspect,
[0054] FIG. 4E shows in the same cross-section a subsequent
alternative optional manufacturing step of a method according to
the second aspect,
[0055] FIG. 4F shows in the same cross-section a further subsequent
alternative optional manufacturing step of a method according to
the second aspect,
[0056] FIG. 4G shows in the same cross-section an alternative
embodiment resulting from a still further subsequent alternative
optional manufacturing step following the step illustrated in FIG.
4F,
[0057] FIG. 5 shows in the same cross-section a first embodiment of
a photo-voltaic element according to the first aspect obtained
after a further manufacturing step of a method according to the
second aspect,
[0058] FIG. 6 shows in the same cross-section a second embodiment
of a photo-voltaic element according to the first aspect,
[0059] FIG. 7 shows in the same cross-section a third embodiment of
a photo-voltaic element according to the first aspect,
[0060] FIG. 8A shows a top-view corresponding to the area IIA of a
fourth embodiment of a photo-voltaic element according to the first
aspect,
[0061] FIG. 8B shows a cross-section according to VIIIB-VIIIB in
FIG. 8A,
[0062] FIG. 9A shows a top-view corresponding to the area IIA of a
semi-finished product obtained after an additional manufacturing
step of a method according to the second aspect,
[0063] FIG. 9B shows a cross-section according to IXB-IXB in FIG.
9A,
[0064] FIG. 10A shows a top-view corresponding to the area IIA of a
semi-finished product obtained after an additional manufacturing
step of a method according to the second aspect,
[0065] FIG. 10B shows a cross-section according to XB-XB in FIG.
10A,
[0066] FIG. 11A shows a top-view corresponding to the area IIA of a
semi-finished product obtained after an additional manufacturing
step of a method according to the second aspect,
[0067] FIG. 11B shows a cross-section according to XIB-XIB in FIG.
11A,
[0068] FIG. 12A shows a top-view corresponding to the area IIA of a
semi-finished product obtained after an additional manufacturing
step of a method according to the second aspect,
[0069] FIG. 12B shows a cross-section according to XIIB-XIIB in
FIG. 12A,
[0070] FIG. 12C shows a portion of the surface of the semi-finished
product of FIG. 4B in more detail,
[0071] FIG. 12D shows a portion of the surface of the semi-finished
product of FIG. 12B in more detail,
[0072] FIG. 13 shows a product obtained after the step of FIG. 12A,
12B,
[0073] FIG. 14A shows a top-view corresponding to the area IIA of a
semi-finished product obtained after an additional manufacturing
step of a method according to the second aspect,
[0074] FIG. 14B shows a cross-section according to XIVB-XIVB in
FIG. 14A,
[0075] FIG. 15A shows a top-view corresponding to the area IIA of a
semi-finished product obtained after an additional manufacturing
step of a method according to the second aspect,
[0076] FIG. 15B shows a cross-section according to XVB-XVB in FIG.
15A,
[0077] FIG. 16 shows a product obtained after the step of FIG. 15A,
15B,
[0078] FIG. 17A shows a top-view corresponding to the area IIA of a
semi-finished product obtained after an additional manufacturing
step of a method according to the second aspect,
[0079] FIG. 17B shows a cross-section according to XVIIB-XVIIB in
FIG. 17A.
DETAILED DESCRIPTION OF EMBODIMENTS
[0080] FIG. 5 schematically shows a photo-voltaic element 1. The
photo-voltaic element 1 comprises a substrate 10 and a stack of
layers arranged thereon. The substrate 10 may be formed of a rigid
material such as a metal (e.g. steel, copper or aluminum), silicon
or glass or of a flexible material such as a polymer, e.g. a
polymer like polyethylene terephthalate (PET), polyethylene
naphthalate (PEN), or polyimide (PI). Also thin metal or glass are
suitable substrates. If the substrate is conducting, an isolating
layer may be deposited on that substrate to isolate the electrode
from the substrate. Dependent on the application a thickness of the
substrate may be selected in the range of a relatively small value
e.g. 50 micron and a relatively large value, e.g. a few mm or more.
The stack of layers subsequently includes at least a first
electrode layer 20, a first charge carrier transport layer 30, an
insulating layer 40, a second electrode layer 50, a second charge
carrier transport layer 60, and a photo-electric conversion layer
70.
[0081] The first electrode layer 20 is provided for receiving
charge carriers of a first polarity. In the embodiment shown the
first electrode layer 20 is an anode, i.e. arranged for receiving
holes as the charge carriers. Dependent on the lateral size of the
photo-voltaic element 1 the first electrode layer 20 may for
example have a thickness in the range of a few tens to a few
hundreds of nanometers or even more. In the embodiment shown the
first electrode layer 20 includes an aluminum sub layer having a
thickness of 190 nm, which is sandwiched between a pair of nickel
layers, each having a thickness of 5 nm. In another example the
first electrode layer is of molybdenum. In an embodiment where the
substrate is provided of a metal, it may also serve as a first
electrode layer 20.
[0082] In the embodiment shown the first charge carrier transport
layer 30 is a hole transport layer, having a thickness in the range
of 10 to 200 nm. In the embodiment shown the hole transport layer
is formed by a nickeloxide layer having a thickness of 50 nm. In
another example the hole transport layer is formed by a MoSe
layer.
[0083] An insulating layer 40 is provided of an organic, e.g. a
polymer, or inorganic insulating material, such as a metal oxide.
Also a stack of materials can be used. Dependent on the material
selected for the insulating layer, it may have a thickness in the
range of 10 to 200 nm for example, but also a substantially thicker
insulating layer may be applied. In the embodiment shown the
insulating layer 40 is provided as a SiO2 layer having a thickness
of 100 nm.
[0084] A second electrode layer 50 for receiving charge carriers of
a second polarity opposite to said first polarity is arranged on
the insulating layer 40. In this case the second electrode layer 50
is a cathode. Any sufficiently conducting material can be used for
this purpose at a thickness depending on the lateral size of the
photo-voltaic element 1. Typically the thickness of the second
electrode layer 50 is of the same order of magnitude as the
thickness of the first electrode layer 20, so that they have
approximately the same conductivity and neither of them forms a
bottleneck. In the embodiment shown the second electrode layer 50
is an aluminum layer with a thickness of 200 nm. In some
embodiments the second electrode layer 50 may have a thickness
greater than that of the first electrode layer 20, e.g. 1.5 times a
thickness of the first electrode layer 20, to compensate for the
presence of the openings provided in the second electrode layer
50.
[0085] A second charge carrier transport layer 60 for transport of
charge carriers having said the second polarity, opposite to the
first polarity layer is arranged upon the second electrode layer
50. In this case the second charge carrier transport layer 60 is an
electron transport layer. The second charge carrier transport layer
60, here an electron transport layer may have a thickness in the
range of a few nm, e.g. 5 nm to a few tens of nm, e.g. 50 nm. In
the embodiment shown the second charge carrier transport layer 60
is a TiO.sub.2 layer having thickness of 15 nm. Other suitable
materials for an electron transport layer are for example
SnO.sub.2, ZrO.sub.2 and ZnO:S.
[0086] A photo-electric conversion layer 70 is provided upon the
second charge carrier transport layer 60. The photo-electric
conversion layer 70 has a plurality of distributed, typically
cylindrical, extensions 72 that extend through the second charge
carrier transport layer 60, the second electrode layer 50 and the
insulating layer 40 to the first charge carrier transport layer 30.
Therewith the photo-electric conversion layer 70 is electrically
coupled to both the first charge carrier transport layer 30 and the
second charge carrier transport layer 60. In this arrangement solar
radiation R does not need to traverse an electrode layer or a
charge carrier transport layer which contributes to an efficient
operation of the photo-voltaic element 1. In the embodiment shown
the extensions 72 have an effective cross-section D.sub.eff in the
range of 0.5 to 10 micron, and have an average pitch in the range
of 1.1 to 5 times their effective cross-section. The effective
cross-section is defined here as the diameter of a circle having an
area corresponding to the cross-sectional area A.sub.O of the
extensions.
I . e . D eff = 4 A .PHI. .pi. ##EQU00002##
[0087] The extensions may have any cross-section, such as circular,
square or triangular. Preferably, a circumference O of the
extensions is less than 10 times the effective diameter D.sub.eff
and even more preferably less than 5 times the effective diameter
D.sub.eff.
[0088] In the embodiment the photo-electric conversion layer is
provided of a perovskite material, such as methylammonium lead
trihalide (CH.sub.3NH.sub.3PbX.sub.3), or Cesium-formamidinum lead
trihalide
(Cs.sub.0.05(H.sub.2NCHNH.sub.2).sub.0.95PbI.sub.2.85Br.sub.0.15).
Alternatively a tin based perovskite material, such as
CH.sub.3NH.sub.3SnI.sub.3 may be used. Also more complex perovskite
materials may be applied, for example containing a combination of
different cations. Also other materials, such as copper indium
gallium selenide (CIGS) are suitable.
[0089] In the embodiment shown the second electrode layer 50 has
anodized edge surfaces 52 facing the extensions 72 of the
photo-electric conversion layer 70. This avoids direct contact
between the second electrode layer and the photo-electric
conversion layer.
[0090] FIG. 4G illustrates an alternative embodiment wherein such
direct contact is avoided. Therein the openings 82 are provided
with an insulating wall 78, e.g. of a ceramic material. The
specific steps for manufacturing this embodiment are described in
more detail below with reference to FIG. 4D to FIG. 4G.
[0091] FIG. 6 shows an embodiment of the photo-voltaic element 1 of
the invention wherein an edge portion 22 of an upper surface of the
first electrode layer 20 is kept free from material of the first
charge carrier transport layer 30 and is provided with a first
electrical contact 25. Also an edge portion 52 of an upper surface
of the second electrode layer 50 is kept free from material of the
second charge carrier transport layer 60 and is provided with a
second electrical contact 55. Another possibility is to remove the
carrier transport layer 30 and isolator 40 with e.g. laser ablation
before deposition of electrode 50, so a contact can be made from
electrode 50 to electrode 20. Also before deposition of charge
carrier transport layer 30 a laser step could be used to interrupt
the electrode 20.
[0092] FIGS. 8A and 8B show a further embodiment of a photo-voltaic
element according to the invention. Therein FIG. 8A shows a
top-view and FIG. 8B shows a cross-section of a portion of the
device according to VIIIB-VIIIB in FIG. 8A. In this further
embodiment the first electrode layer 20, the first charge carrier
transport layer 30, the insulating layer 40 and the second
electrode layer 50 are provided as a plurality of layer segments.
Therein a plurality of lateral sub-stack segments is formed. By way
of example two lateral sub-stack segments A, B are shown in this
case. However in practice the photo-voltaic element may have a
larger number of lateral sub-stack segments C, D, . . . e.g. 10 or
100 or more, depending on a required lateral size of the
photo-voltaic element.
[0093] As shown in FIG. 8B each layer segment A,B comprises a first
electrode layer segment 20A, 20B, a first charge carrier transport
layer segment 30A, 30B, an insulating layer segment 40A, 40B and a
second electrode layer segment 50A, 50B. The second charge carrier
transport layer 60 and the photo-electric conversion layer 70 are
formed as continuous layers. A second electrode layer segment 50A
of a lateral sub-stack segment A extends over a first electrode
layer segment (20B) in a neighboring sub-stack segment B. Therewith
an electrical connection is formed between the second electrode
layer segment 50A of the lateral sub-stack segment A and the first
electrode layer segment 20B in the neighboring lateral sub-stack
segment. In this way the photo-voltaic element is formed as a
plurality of serially connected modules, which makes it possible to
reduce resistive losses as compared to a photo-voltaic element that
is not partitioned into serially connected modules. It could
alternatively be contemplated to serially arrange a plurality of
smaller photo-voltaic elements. It is however an advantage of the
embodiment of FIG. 8A, 8B that external connection elements are
avoided. A photo-voltaic element as shown in FIG. 8A, 8B could for
example be provided as a single elongate product applied on a foil,
e.g. delivered in a length of tens to hundreds of meter on a
roll.
[0094] As shown in FIG. 7 additional layers may be provided. In the
embodiment of FIG. 7 for example a barrier 90 is arranged over said
photo-electric conversion layer 70. Suitable materials for the
barrier are metal oxides, such as SiOx and SiNx. In practice the
barrier 90 may comprise a plurality of layers, such as a stack of
inorganic layers having a mutually different composition. Also a
combination of inorganic layers and organic layers may be used. For
example a barrier 90 may be formed by a first and a second
inorganic layer that sandwich an organic layer. For a good light in
coupling it is preferred that the materials used for the barrier 90
have a refractive index lower than that of the photo-electric
conversion layer 70.
[0095] In the embodiment shown light in coupling is further
improved by a light in coupling structure 100 arranged over the
barrier 90. In the embodiment shown the light in coupling structure
comprises a plurality of light in coupling elements 102A, 102B. For
example semi-spherical or pyramidal shaped light in coupling
elements may be used.
[0096] A method of manufacturing a photo-voltaic element is now
disclosed with reference to FIGS. 1 to 5.
[0097] FIG. 1A, 1B show the intermediate product obtained after a
first three steps. Therein FIG. 1A shows a top-view and FIG. 1B
shows a cross-section according to IB-IB in FIG. 1A.
[0098] Therein a substrate is 10 is provided in a first step S1.
Then in a second step S2 a stack of layers is deposited thereon
that comprise at least in the order named a first electrode layer
20, a first charge carrier transport layer 30, an insulating layer
40, a second electrode layer 50 and a second charge carrier
transport layer.
[0099] The first electrode layer 20 is provided for receiving
charge carriers of a first polarity. The first electrode layer 20
may for example be an anode, i.e. arranged for receiving holes as
the charge carriers. Alternatively the first electrode layer 20 may
be a cathode, i.e. arranged for receiving electrons as the charge
carriers. In an embodiment the first electrode layer 20 is
deposited with a PVD (physical vapor deposition) method, for
example using E-beam PVD. In this example the first electrode layer
20 was provided as a stack of sub-layers obtained by subsequently
depositing a first sub-layer of nickel having a thickness of 5 nm,
an aluminum layer having a thickness of 190 nm and a second
sub-layer of nickel also having a thickness of 5 nm. Then
spin-coating (1000 rpm) was used to deposit a NiO layer as the
first charge carrier transport layer 30, here a hole transport
layer.
[0100] An insulating layer 40 was then deposited in a first and a
second stage. In the first of these stages a first, 100 nm thick,
sublayer of SiOx was deposited by electron-beam deposition and in
the second stage a second sublayer of SiOx, also having a thickness
of 100 nm was deposited by PECVD. Then a second electrode layer 50,
here a cathode layer of aluminum at a thickness of 200 nm was
formed using the same method and conditions as those applied for
the deposition of the aluminum sub-layer of the first electrode
layer 20.
[0101] A second charge carrier transport layer 60, here an electron
transport layer was then deposited. In this case electron-beam
vapor deposition was used to deposit a TiOx layer with a thickness
of 15 nm of linear titanium dioxide (TiOx).
[0102] The insulating layer 40 and the layers 50, 60 form a
sub-stack having an upper surface 64. In a third step S3, here
using spin coating a resist layer 80, here a photo-resist layer
having a thickness of 1.6 micron was deposited on this upper
surface 64. In other implementations the resist layer may be an
imprint-resist layer.
[0103] FIG. 2A, 2B show a subsequent step S4. Therein FIG. 2A shows
a top-view of an intermediate product resulting from this step S4
and FIG. 2B shows a cross-section according to IIB-IIB in FIG. 2A.
In this subsequent step regularly distributed openings 82 giving
access to the upper surface 64 are formed in the resist layer 80.
In this embodiment contact lithography was used for this purpose.
Using the method described herewith samples were prepared having
openings with diameter in the range of 0.5-5 .mu.m and a distance
between neighboring openings in the range of 1-5 .mu.m. Therewith a
pitch between 1 and 10 gm is obtained. The openings having an
effective cross-section D in the range of 0.5 to 10 micron, and
have an average pitch in the range of 1.1 to 5 times the effective
cross-section.
[0104] Instead of patterning an originally homogeneous resist
layer, it is alternatively possible to directly depositing the
resist layer in the desired pattern, for example using a printing
technique.
[0105] FIGS. 3A and 3B show a subsequent step S5, wherein material
of the sub-stack 40, 50, 60 facing the openings 82 is selectively
removed. Therein FIG. 3A shows a top-view of the semi-finished
product obtained after this step S5 and FIG. 3B shows a
cross-section according to IIIB-IIIB in FIG. 3A. Step S5 involves
etching the upper layers 50, 60 by plasma etching. Then the
insulating SiOx layer is etched with a further plasma etching
process. The photo-resist layer 80 is then fully removed (Step S6),
for example by oxygen plasma-etching as illustrated in FIGS. 4A and
4B. Therein FIG. 4A is a top-view and FIG. 4B shows a cross-section
according to IVB-IVB in FIG. 4A.
[0106] As shown in FIG. 5, in a step S7, subsequent to this step
S6, a photo-electric conversion layer 70 is deposited (for example
by spin-coating) and cured.
[0107] Optional pre-processing steps, S6A and S6B may be performed
after removal of the resist layer 80 and before deposition of the
photo-electric conversion layer 70.
[0108] A first optional pre-processing step S6A is illustrated in
FIG. 4B. Therein an edge surface 52 of the second electrode layer
50 is anodized. This edge surface 52 was formed by the step of
etching S5. This anodization process an insulating layer is formed
on the edge surface 52 therewith avoiding a direct contact between
the second electrode layer 50 and the photo-electric conversion
layer 70.
[0109] FIG. 4C illustrates a second optional pre-processing step
S6B. Therein to facilitate the deposition in step S7, an atomic
layer deposition process (ALD) may be used to deposit a thin growth
layer 74, e.g. applying a TiO.sub.2 layer with a few sALD
cycles.
[0110] FIG. 4D-4G shows an alternative approach for preventing a
direct electrical contact between the second electrode layer 50 and
the photo-electric conversion layer 70. After removal (S6) of the
patterned resist layer 80 as shown in FIG. 4D, a layer 76 of an
insulating material is conformally deposited (Step S6C) on the
semi-finished product of FIG. 4D, therewith obtaining the
semifinished product of FIG. 4E. Then an anisotropic etch step S6D,
e.g. a plasma etch step is applied. The anisotropic etch step 56D
removes the insulating material from the surface of the second
charge carrier transport layer 60 and from the surface portions of
the first charge carrier transport layer 30 within the openings 82
but keeps a layer of the insulating material on the walls of the
openings 82 intact. Subsequent to this step S6D the photo-electric
conversion layer can be deposited (S6E) as shown in FIG. 4G.
[0111] Upon completion the substrate 10 may be removed. For example
this may be the case if an electrode layer, e.g. the first
electrode layer 20 provides sufficient structural integrity.
Alternatively, or in addition mechanical support may be provided by
further layers applied on the photo-electric conversion layer
70.
[0112] FIGS. 9A, 9B, 10A, 10B, 11A, 11B, 12A, 12B and 13 show a
further alternative embodiment of a method of manufacturing.
Therein FIG. 9A, 9B show a semi-finished product that is obtained
after step S15 of this embodiment. The steps of this embodiment up
to and including S15 of this embodiment correspond to those
disclosed herein for steps S1-S5 of the embodiment of FIGS. 1A, 1B,
2A, 2B and 3A, 3B, except for the fact that the step corresponding
to step S2, does not include deposition of a charge carrier
transport layer 60. Instead the charge carrier transport layer 60
is deposited in another stage of the process as is discussed with
reference to FIG. 12A, 12B. Following step S15, in step S16 shown
in FIG. 10A, 10B, an opening 54 is formed in the second electrode
layer 50. This can be achieved by a wet etching step selected for
the second electrode layer 50. For example using a PES (Phosphoric
Acid, Acetic Acid, Sulphoric acid The last is now often replaced
with Nitric acid) solution in case of a second electrode 50 formed
by an aluminum layer or having an aluminum layer as a main layer
which is sandwiched between auxiliary layers, e.g. formed by
molybdenum. Alternatively, if the second electrode 50 is formed by
conductive oxide layer, such as ITO, a HCL-FeCl solution may be
used as the etching agent. Still alternatively an isotropic or
anisotropic plasma etching step may be used in step S16A.
[0113] In a next step S16B, as shown in FIG. 11A, 11B, an opening
44 is formed in the insulating layer 40, to expose the surface of
the charge carrier transport layer 30. An isotropic plasma etching
step, for example using CF.sub.4/O.sub.2 may be applied. Also wet
etching can be used. E.G. NH.sub.4F if a siliconoxide isolator is
used.
[0114] In a further step S16C, a second charge carrier transport
layer 60, is deposited in an electroplating process, therewith
using the layer 50 as the electrode. Due to the curved edge 55 of
the opening formed in the electrode 50, an increased electric field
is obtained that enhances the deposition speed near the opening. By
way of example, a hole transport layer may be deposited as the
charge carrier transport layer 60, e.g. CuSCN using a solution of
CuSO4/Nitrilotriacetic acid/KSCN. Alternatively, the charge carrier
transport layer 60 may be deposited from an ionic liquid.
[0115] Then in step S17, which is comparable to step S7 as
disclosed with reference to FIG. 5, a photo-electric conversion
layer 70 is deposited.
[0116] In the photo-voltaic element so obtained, the extensions 72
taper outward in a direction from the first charge carrier
transport layer 30 towards the second charge carrier layer 60. As a
result of the electroplating process used for the second charge
carrier transport layer 60, the material thereof covers a surface
of the second electrode 50 surrounding the extensions 72. Using an
isotropic etching process, the openings formed will taper outward
towards the second charge carrier layer 60 with an angle of
approximately 45 degrees, so that the perimeter of the opening at
the contact-surface of the first charge carrier transport layer is
displaced with respect to the perimeter at the level of the surface
of the second charge carrier transport layer is of the order of
magnitude of the total thickness of the layers in which the opening
is formed. For example, if the effective cross-section D.sub.eff of
the opening with which the first charge carrier layer 30 is to be
exposed, as defined by the mask used for etching is 1 micron, and
the thicknesses of the second electrode layer 50 and the insulating
layer 40 are 100 nm and 300 nm respectively, then at the plane
surface of the second charge carrier transport layer 60, the
cross-section Dout may be about 1.8 micron. As the electroplated
second charge carrier layer 60 also has a portion 65 that extends
over the tapering wall of the opening the contact surface of the
second charge carrier layer 60 available for the photovoltaic layer
70 to be deposited in the next step is increased as compared to the
situation in FIG. 4B for example. In the embodiment of FIG. 12B,
the available contact surface At formed by the tapering hole in the
second charge carrier transport layer is
[0117] At=.pi.H(Deff+.alpha.H), wherein H is the height of the
electrode layer 50 and .alpha. is the inclination factor with which
the diameter widens towards the surface 67 of the second charge
carrier transport layer 60. I.e. the inclination factor .alpha. is
defined by
.alpha.=(Dout-Deff)/2H.
[0118] This additional surface At is illustrated as the hatched are
At in FIG. 12D This is compared with the situation in FIG. 4B. In
that case, an annulus having an inner diameter Deff and an outer
diameter Dout would be additionally available at the surface 67 of
the second charge carrier transport layer. The surface Ac of this
area between the dashed circle in FIG. 12C and area removed by the
opening to give access to the first charge carrier transport layer
30 is equal to
Ac=1/2 .pi..alpha.DH+.pi..alpha..sup.2H.sup.2
Hence the difference in the surface At and the surface Ac is equal
to
.DELTA.A=At-Ac=.pi.(1-.alpha./2)DH+.pi..alpha.(1-.alpha.)H.sup.2
Accordingly, if a is in a range between 0 and 1, the contact
surface area of the second charge carrier layer 60 is always
improved. Furthermore an improvement may be obtained in the range
1<.alpha.<2, provided that:
.pi.(1-.alpha./2)D>.pi..alpha.(1-.alpha.)H. It is noted that the
height of the second charge carrier transport layer 60 typically is
substantially smaller than the height of the second electrode
layer. However, for visibility the height of this layer 60 is
exaggerated.
[0119] An alternative embodiment of the method is illustrated in
FIG. 14A, 14B, 15A, 16B.
[0120] The preparatory steps with which the semi-finished product
as shown in FIG. 14A, 14B is obtained after step S26, differ from
those used for the semi-finished product of FIG. 11A, 11B, in that
no first charge-carrier transport layer 30 is deposited. Instead,
in the subsequent step S27 as shown in FIG. 15A, 15B, the first
charge-carrier transport layer 30 is deposited locally on the
exposed portions of the surface of the first electrode layer 20,
using an electroplating process. E.g. electroplating of an ETL like
SnO.sub.2 from a solution of 20 mM tin chloride (SnCl.sub.2) and 75
mM nitric acid Starting from here, also the second charge-carrier
transport layer 60 can be deposited, as shown in FIG. 12A, 12B and
a photo-electric conversion layer 70 can be deposited as shown in
FIG. 13. The second charge carrier transport layer, in this case a
HTL, may be deposited for example from CuSCN using a solution of
CuSO4/Nitrilotriacetic acid/KSCN. The product so obtained, as shown
in FIG. 16, is characterized in that the first charge carrier layer
30 is absent in areas of the first electrode layer 20 covered by
the insulating layer 40. In an alternative embodiment,
electrodeposition may be used to deposit a hole transport layer as
the first charge carrier transport layer 30 and to deposit an
electron transport layer as the second charge carrier transport
layer 60.
[0121] It is still further possible that only the first
charge-carrier layer 30 is deposited by electro-plating. For
example, starting from a semi-finished product, differing from the
semi-finished product of FIG. 2A, 2B, in that a first charge
carrier transport layer 30 is absent, an opening may be formed in
the layers 40, 50 and 60 in steps as described with reference to
FIG. 3A, 3B, or as described with reference to FIG. 10A, 10B, 11A,
11B, and subsequently an electro-plating step S37 can be used to
deposit a first charge carrier layer 30 on the exposed portions of
the surface of the first electrode 20, as shown in FIG. 17A, 17B.
Also in this case, the product which is obtained is characterized
in that the first charge carrier layer 30 is absent in areas of the
first electrode layer 20 covered by the insulating layer 40.
[0122] While the invention has been illustrated and described in
detail in the drawings and foregoing description, such illustration
and description are to be considered illustrative and exemplary and
not restrictive; the invention is not limited to the disclosed
embodiments. Other variations to the disclosed embodiments can be
understood and effected by those skilled in the art in practicing
the claimed invention, from a study of the drawings, the disclosure
and the appended claims.
[0123] In the claims the word "comprising" does not exclude other
elements or steps, and the indefinite article "a" or "an" does not
exclude a plurality. A single processor or other unit may fulfill
the functions of several items recited in the claims. The mere fact
that certain measures are recited in mutually different claims does
not indicate that a combination of these measures cannot be used to
advantage. Any reference signs in the claims should not be
construed as limiting the scope.
* * * * *