U.S. patent application number 14/135621 was filed with the patent office on 2014-04-24 for single junction type cigs thin film solar cell and method for manufacturing the thin film solar cell.
This patent application is currently assigned to Electronics and Telecommunications Research Institute. The applicant listed for this patent is Electronics and Telecommunications Research Institute. Invention is credited to Yong-Duck CHUNG, Won Seok HAN.
Application Number | 20140109963 14/135621 |
Document ID | / |
Family ID | 45995311 |
Filed Date | 2014-04-24 |
United States Patent
Application |
20140109963 |
Kind Code |
A1 |
CHUNG; Yong-Duck ; et
al. |
April 24, 2014 |
SINGLE JUNCTION TYPE CIGS THIN FILM SOLAR CELL AND METHOD FOR
MANUFACTURING THE THIN FILM SOLAR CELL
Abstract
Provided is a single junction type GIGS thin film solar cell,
which includes a CIGS light absorption layer manufactured using a
single junction. The single junction type GIGS thin film solar cell
includes a substrate, a back contact deposited on the substrate, a
light absorption layer deposited on the back contact and including
a P type GIGS layer and an N type GIGS layer coupled to the P type
CIGS layer using a single junction, and a reflection prevention
film deposited on the light absorption layer.
Inventors: |
CHUNG; Yong-Duck; (Daejeon,
KR) ; HAN; Won Seok; (Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Electronics and Telecommunications Research Institute |
Daejeon |
|
KR |
|
|
Assignee: |
Electronics and Telecommunications
Research Institute
Daejeon
KR
|
Family ID: |
45995311 |
Appl. No.: |
14/135621 |
Filed: |
December 20, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13207825 |
Aug 11, 2011 |
8637765 |
|
|
14135621 |
|
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Current U.S.
Class: |
136/256 |
Current CPC
Class: |
H01L 31/02168 20130101;
H01L 31/03923 20130101; Y02E 10/541 20130101; Y02P 70/521 20151101;
Y02E 10/547 20130101; H01L 31/068 20130101; H01L 31/0322 20130101;
Y02P 70/50 20151101 |
Class at
Publication: |
136/256 |
International
Class: |
H01L 31/032 20060101
H01L031/032 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 3, 2010 |
KR |
10-2010-0108880 |
Claims
1. A single junction type GIGS (Cu (In, Ga) Se.sub.2) thin film
solar cell comprising: a substrate; a back contact disposed on the
substrate; a light absorption layer disposed on the back contact
and comprising a single junction diode comprising a GIGS thin film;
and a reflection prevention film disposed on the light absorption
layer.
2. The single junction type GIGS thin film solar cell of claim 1,
wherein the light absorption layer comprises: a P type GIGS layer
disposed on the back contact; and an N type GIGS layer disposed on
the P type GIGS layer using a single junction.
3. The single junction type GIGS thin film solar cell of claim 1,
further comprising a window layer disposed on the N type GIGS layer
between the light absorption layer and the reflection prevention
film.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a Divisional of U.S. application Ser. No.
13/207,825, filed on Aug. 11, 2011, and allowed on Sep. 25, 2013,
the subject matter of which is incorporated herein by reference.
The parent application Ser. No. 13/207,825 claims the benefit of
Korean patent application number 10-2010-0108880, filed on Nov. 3,
2010, the disclosure of which is incorporated herein in its
entirety by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a single junction type CIGS
(Cu (In, Ga) Se.sub.2) thin film solar cell and a method for
manufacturing the single junction type CIGS thin film solar cell,
and more particularly, to a single junction type CIGS thin film
solar cell including a CIGS light absorption layer manufactured
using a single junction, and a method for manufacturing the single
junction type CIGS thin film solar cell.
[0003] In recent years, interest in solar cells is increasing
because of energy and environmental issues.
[0004] Solar cells, which absorb sunlight to convert it to
electricity, are classified into solar heat cells that use solar
heat to generate steam for rotating a turbine, and photovoltaic
cells that use the nature of a semiconductor to convert the energy
of sunlight into electrical energy.
[0005] In general, solar cells are referred to as photovoltaic
cells (hereinafter, solar cells).
[0006] The above description relates to the related art for
clarifying the present invention, and the related art is distinct
from the prior art.
SUMMARY OF THE INVENTION
[0007] Embodiments of the present invention are directed to a
single junction type CIGS thin film solar cell including a single
junction CIGS light absorption layer having a P type CIGS
semiconductor layer and an N type CIGS semiconductor layer, and a
method for manufacturing the single junction type CIGS thin film
solar cell.
[0008] Embodiments of the present invention are also directed to a
single junction type CIGS thin film solar cell that includes a
light absorption layer having a P type CIGS layer and an N type
CIGS layer coupled to the P type CIGS layer to form a single
junction, and a method for manufacturing the single junction type
CIGS thin film solar cell, which make it possible to prevent
surface and interface contamination due to a buffer layer and
environmental pollutions due to a toxic element, and to improve the
performance of the solar cell.
[0009] In one embodiment, a single junction type CIGS (Cu (In, Ga)
Se.sub.2) thin film solar cell includes: a substrate; a back
contact disposed on the substrate; a light absorption layer
disposed on the back contact and comprising a single junction diode
comprising a CIGS thin film; and a reflection prevention film
disposed on the light absorption layer.
[0010] The light absorption layer may include: a P type CIGS layer
disposed on the back contact; and an N type CIGS layer disposed on
the P type CIGS layer using a single junction.
[0011] The single junction type CIGS thin film solar cell may
further include a window layer disposed on the N type CIGS layer
between the light absorption layer and the reflection prevention
film.
[0012] in another embodiment, a method for manufacturing a single
junction type CIGS (Cu (In, Ga) Se.sub.2) thin film solar cell
includes: preparing a substrate; depositing a back contact of
molybdenum (Mo) on the substrate by using a sputtering method;
depositing an P type CIGS layer on the back contact by using a
co-evaporation method; depositing an N type CIGS layer on the P
type CIGS layer; and depositing a reflection prevention film of
MgF.sub.2 on the N type CIGS layer by using an electron-beam
evaporation method.
[0013] The depositing of the N type CIGS layer may include mixing
an alkali metal with a selenide, and using a co-evaporation
method.
[0014] The alkali metal may include natrium (Na).
[0015] The selenide may include Na.sub.2Se.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 illustrates a schematic view of a single junction
type CIGS thin film solar cell according to an embodiment of the
present invention.
[0017] FIG. 2 illustrates a schematic view of a single junction
type CIGS thin film solar cell according to another embodiment of
the present invention.
DESCRIPTION OF SPECIFIC EMBODIMENTS
[0018] Hereinafter, a single junction type CIGS (Cu (In, Ga)
Se.sub.2) thin film solar cell and a method for manufacturing the
single junction type CIGS thin film solar cell in accordance with
the present invention will be described in detail with reference to
the accompanying drawings.
[0019] Hereinafter, the present invention will be described in more
detail through embodiments. The embodiments are merely for
exemplifying the present invention, and the right protection scope
of the present invention is not limited by the embodiments.
[0020] In the drawings, the thicknesses of lines or the sizes of
elements may be exaggeratedly illustrated for clarity and
convenience of description. Moreover, the terms used henceforth
have been defined in consideration of the functions of the present
invention, and may be altered according to the intent of a user or
operator, or conventional practice. Therefore, the terms should be
defined on the basis of the entire content of this
specification.
[0021] FIG. 1 illustrates a schematic view of a single junction
type CIGS thin film solar cell according to an embodiment of the
present invention. FIG. 2 illustrates a schematic view of a single
junction type CIGS thin film solar cell according to another
embodiment of the present invention.
[0022] Referring to FIG. 1, a single junction type CIGS thin film
solar cell according to an embodiment of the present invention
includes a substrate 1, a back contact 2 deposited on the substrate
1, a light absorption layer 3, and a reflection prevention film 4
deposited on the light absorption layer 3. The light absorption
layer 3 includes a P type CIGS layer 31 and an N type CIGS layer
32, which are coupled to each other to form a single junction and
are deposited on the back contact 2.
[0023] The substrate 1 is formed of sodalime glass. Alternatively,
the substrate 1 may be a ceramic substrate including alumina or
quartz; a metal substrate including stainless steel, Cu tape, Cr
steel, Kovar (Ni/Fe alloys), Ti, ferritic steel, or Mo; or a
polymer including Kapton, Upilex, or ETH-PI.
[0024] The back contact 2 is formed of Mo. This is because Mo has
high electrical conductivity, can be in ohmic contact with CIGS,
and has high temperature stability in Se atmosphere.
[0025] A Mo thin film is formed using a direct current (DC)
sputtering method. The Mo thin film has low resistivity as an
electrode, and great adhering force to the substrate 1 to prevent
peeling due to a difference in thermal expansion coefficient.
[0026] An impurity diffusion barrier film (not shown) may be
disposed between the substrate 1 and the back contact 2.
[0027] As described above, the light absorption layer 3 includes
the P type CIGS layer 31 and the N type CIGS layer 32, which are
coupled to each other form a single junction.
[0028] The P type CIGS layer 31 is formed through a CuInGaSe.sub.2
thin film forming process, and the N type CIGS layer 32 is formed
by mixing an alkali metal and a selenide.
[0029] CuInGaSe.sub.2 thin film forming methods include an
evaporation method as a physical method, a sputtering/selenization
method, and an electroplating method as a chemical method. Each
method may employ various manufacturing methods according to the
type of a starting material (such as a metal or a binary
compound).
[0030] According to the current embodiment, four metal elements Cu,
In, Ga, and Se are used as starting materials in a co-evaporation
method. Unlike physical/chemical thin film manufacturing methods in
the related art, nano-particles (such as powder and colloid) may be
synthesized on a Mo substrate, and be mixed with solvent, and be
processed using screen printing and reaction sintering to
manufacture a light absorption layer.
[0031] Na as an alkali metal is mixed with Na.sub.2Se as a selenide
to deposit the N type CIGS layer 32 using the co-evaporation
method. Although Na and Na.sub.2Se are used in the current
embodiment, a group IA element such as K, Rb, Cs, and Fr as alkali
metals having similar characteristics, and NaF, Na.sub.2S, or
Na.sub.2Se may be used in another embodiment of the present
Invention.
[0032] The reflection prevention film 4 is formed of MgF.sub.2
using an electron-beam evaporation method as a physical thin film
manufacturing method. The reflection prevention film 4 reduces a
reflection loss of sunlight absorbed by the solar cell to increase
the efficiency of the solar cell by approximately 1%.
[0033] A grid electrode 5 for collecting a current on a surface of
the solar cell is formed of Al or Ni/Al.
[0034] Since the amount of absorbed sunlight is decreased by the
area of the grid electrode 5, the efficiency of the solar cell may
be decreased. Thus, the grid electrode 5 is disposed at a side of
the reflection prevention film 4.
[0035] Referring to FIG. 2, a window layer 6 may be deposited on
the N type CIGS layer 32 between the light absorption layer 3 and
the reflection prevention film 4.
[0036] Since the window layer 6 functions as a transparent
electrode on a front surface of the solar cell, the window layer 6
has high light transmissivity and high electrical conductivity.
[0037] A ZnO thin film used as a transparent electrode has an
energy band gap of approximately 3.3 eV and a high light
transmissivity of approximately 80% or greater. Furthermore, the
ZnO thin film may be doped with Al or B to have a low resistance of
approximately 10.sup.-4 .OMEGA.cm or less. When the ZnO thin film
is doped with B, light transmissivity increases in a near infrared
region to increase a short circuit current.
[0038] The ZnO thin film may be deposited using a radio frequency
(RF) sputtering method with a ZnO target, or using a reactive
sputtering method with a Zn target, or using a metal organic
chemical vapor deposition method.
[0039] A double structure that an indium tin oxide (ITO) thin film
having excellent electro-optical characteristics is deposited on a
ZnO thin film may be used.
[0040] A solar cell according to an embodiment of the present
invention will now be compared with a solar cell in the related
art.
[0041] A light absorption layer of the solar cell in the related
art includes only a CuInGaSe.sub.2 thin film that is a P type
semiconductor forms a PN junction with a ZnO thin film that is an
N-type semiconductor and is used as a window layer.
[0042] However, since the CuInGaSe.sub.2 thin film is quite
different from the ZnO thin film in lattice constant and energy
band, a buffer layer is necessary therebetween for a junction
without a defect.
[0043] The buffer layer is formed of CdS. However, Cd is poisonous,
and a wet chemical process is used for the buffer layer, unlike
other thin films.
[0044] Thus, toxic materials are used for removing surface and
interface contamination due to a hetero junction, and the solar
cell may be degraded.
[0045] In the light absorption layer 3 of the solar cell according
to the embodiment of the present invention, since the P type CIGS
layer 31 is coupled to the N-type CIGS layer 32 to form a single
junction, the quality of the thin film is improved, and thus, the
performance of the solar cell is improved. In addition, since CdS
constituting a buffer layer is not used, environmental pollutions
can be prevented.
[0046] As described above, according to the embodiment of the
present invention, the P type CIGS layer 31 is coupled to the
N-type CIGS layer 32 to form the solar cell including the light
absorption layer 3 in a single junction structure, and thus,
surface and interface contamination due to a buffer layer and
environmental pollutions due to a toxic element can be prevented,
and the performance of the solar cell can be improved.
[0047] While the present invention has been described with respect
to the specific embodiments, it will be apparent to those skilled
in the art that various changes and modifications may be made
without departing from the spirit and scope of the invention as
defined in the following claims.
* * * * *