U.S. patent application number 16/291174 was filed with the patent office on 2020-09-10 for light-emitting diode package structure and method for manufacturing the same.
This patent application is currently assigned to Chung Yuan Christian University. The applicant listed for this patent is Chung Yuan Christian University. Invention is credited to Chi-An CHEN, Cheng-Yi HUANG, Yeeu-Chang LEE, Cheng-An LIN, Yi-Tang SUN.
Application Number | 20200287100 16/291174 |
Document ID | / |
Family ID | 1000005047099 |
Filed Date | 2020-09-10 |
United States Patent
Application |
20200287100 |
Kind Code |
A1 |
LIN; Cheng-An ; et
al. |
September 10, 2020 |
LIGHT-EMITTING DIODE PACKAGE STRUCTURE AND METHOD FOR MANUFACTURING
THE SAME
Abstract
Disclosed herein are a light-emitting diode (LED) package
structure and a method producing the same. The LED package
structure includes a substrate; and a light-emitting unit disposed
on the substrate. The light-emitting unit comprises a gallium
nitride-based semiconductor, and a polymeric layer encapsulating
the gallium nitride-based semiconductor. Also disclosed herein is a
method of producing the LED package structure. The method
comprises: providing a substrate; electrically connecting a gallium
nitride-based semiconductor onto the substrate; overlaying the
gallium nitride-based semiconductor with a slurry comprising a
resin and a plurality of composite fluorescent gold nanocluster;
and curing the slurry overlaid on the gallium nitride-based
semiconductor to form a solidified polymeric layer.
Inventors: |
LIN; Cheng-An; (Taoyuan
City, TW) ; LEE; Yeeu-Chang; (Taoyuan City, TW)
; HUANG; Cheng-Yi; (Taoyuan City, TW) ; CHEN;
Chi-An; (Taoyuan City, TW) ; SUN; Yi-Tang;
(Taoyuan City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Chung Yuan Christian University |
Taoyuan City |
|
TW |
|
|
Assignee: |
Chung Yuan Christian
University
Taoyuan City
TW
|
Family ID: |
1000005047099 |
Appl. No.: |
16/291174 |
Filed: |
March 4, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 2933/0066 20130101;
H01L 33/32 20130101; H01L 2933/005 20130101; C09K 11/025 20130101;
H01L 33/504 20130101; H01L 2933/0041 20130101; H01L 33/62 20130101;
H01L 33/56 20130101 |
International
Class: |
H01L 33/50 20060101
H01L033/50; H01L 33/56 20060101 H01L033/56; H01L 33/62 20060101
H01L033/62; H01L 33/32 20060101 H01L033/32; C09K 11/02 20060101
C09K011/02 |
Claims
1. A light-emitting diode (LED) package structure, comprising, a
substrate; and a light-emitting unit disposed on the substrate,
wherein the light-emitting unit comprises: a gallium nitride-based
semiconductor configured to emit a light having a wavelength that
is shorter than 395 nm; and a polymeric layer encapsulating the
gallium nitride-based semiconductor, wherein the polymeric layer
comprises a resin, at least one composite fluorescent gold
nanocluster dispersed in the resin, and a plurality of luminescent
carbon nanoparticles dispersed in the resin and respectively
emitting a light of a wavelength ranging from 400 nm to 500 nm;
wherein each composite fluorescent gold nanocluster comprises, a
gold nanocluster; and a capping layer composed of a matrix made of
a benzene-based compound, and a plurality of phosphine-based
compounds distributed across the matrix, wherein the capping layer
encapsulates at least a portion of an outer surface of the gold
nanocluster.
2. (canceled)
3. (canceled)
4. (canceled)
5. The LED package structure of claim 1, wherein the benzene-based
compound is selected from the group consisting of benzene,
alkylbenzene, halobenzene, phenol, benzoic acid, acetophenone,
methyl benzoate, anisole, aniline, nitrobenzene, benzonitrile,
benzamide, benzenesulfonic acid, naphthalene, and anthracene.
6. The LED package structure of claim 5, wherein the alkylbenzene
is toluene, cumene, ethylbenzene, styrene, or xylene; and the
halobenzene is fluorobenzene, chlorobenzene, bromobenzene, or
iodobenzene.
7. The LED package structure of claim 1, wherein the plurality of
phosphine-based compounds is selected from the group consisting of
phosphine, phosphine oxide, phosphonium, diphosphine, triphosphine,
alkyl phosphine, cycloalkyl phosphine, aryl phosphine, aryl
phosphine oxide, phenyl phosphine, bidentate phosphine, silicone
derivative of phosphine, siloxane or polysilane derivative of
phosphine, and olefinic phosphine.
8. The LED package structure of claim 7, wherein the alkyl
phosphine is trioctylphosphine (TOP); the aryl phosphine oxide is
trioctylphosphine oxide (TOPO); and the phenyl phosphine is
triphenylphosphine (TPP).
9. A method of producing the LED package structure, comprising, (a)
providing a substrate; (b) electrically connecting a gallium
nitride-based semiconductor onto the substrate, in which the
gallium nitride-based semiconductor is configured to emit a light
having a wavelength that is shorter than 395 nm; (c) overlaying the
gallium nitride-based semiconductor with a slurry comprising a
resin, a plurality of composite fluorescent gold nanoclusters, and
a plurality of luminescent carbon nanoparticles dispersed in the
resin and respectively emitting a light of a wavelength ranging
from 400 nm to 500 nm; and (d) curing the slurry overlaid on the
gallium nitride-based semiconductor for a sufficient time to form a
solidified polymeric layer, wherein the plurality of composite
fluorescent gold nanoclusters are dispersed in the resin, wherein
each composite fluorescent gold nanocluster comprises, a gold
nanocluster; and a capping layer composed of a matrix made of a
benzene-based compound, and a plurality of phosphine-based
compounds distributed across the matrix, wherein the capping layer
encapsulates at least a portion of an outer surface of the gold
nanocluster.
10. (canceled)
11. (canceled)
12. (canceled)
13. The method of claim 9, wherein the benzene-based compound is
selected from the group consisting of benzene, alkylbenzene,
halobenzene, phenol, benzoic acid, acetophenone, methyl benzoate,
anisole, aniline, nitrobenzene, benzonitrile, benzamide,
benzenesulfonic acid, naphthalene, and anthracene
14. The method of claim 9, wherein the alkylbenzene is toluene,
cumene, ethylbenzene, styrene, or xylene; and the halobenzene is
fluorobenzene, chlorobenzene, bromobenzene, or iodobenzene.
15. The method of claim 9, wherein the plurality of phosphine-based
compounds is selected from the group consisting of phosphine,
phosphine oxide, phosphonium, diphosphine, triphosphine, alkyl
phosphine, cycloalkyl phosphine, aryl phosphine, aryl phosphine
oxide, phenyl phosphine, bidentate phosphine, silicone derivative
of phosphine, siloxane or polysilane derivative of phosphine, and
olefinic phosphine.
16. The method of claim 15, wherein the alkyl phosphine is
trioctylphosphine (TOP); the aryl phosphine oxide is
trioctylphosphine oxide (TOPO); and the phenyl phosphine is
triphenylphosphine (TPP).
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present disclosure in general relates to the field of
light-emitting diode (LED) devices. More particularly, the present
disclosure relates to an LED package structure, which comprises a
plurality of composite fluorescent gold nanoclusters serving as
wavelength-convertible materials.
2. Description of Related Art
[0002] White light-emitting diodes (white LEDs) are a relatively
recent innovation resulted from a decade search of an improved LED
useful for various displaying devices. In general, white LEDs are
constructed using wavelength-convertible materials, which can
absorb radiation emitted from the LED and re-emit radiation in a
different wavelength (i.e., color). U.S. Pat. No. 5,998,925 teaches
white LEDs comprising one or more phosphor materials capable of
converting the wavelength of its light source to light in another
desired color. Typically, an LED chip or die emits blue light, in
which a portion of the blue light is absorbed by phosphors that
re-emit yellow light or any combination of green, red and yellow
lights. In the meantime, the portion of the blue light not absorbed
by the phosphors may be combined with the light emitted from the
phosphors thereby gives a nearly white light in the human eyes.
[0003] Nevertheless, the wavelength-convertible materials in white
LEDs--often are phosphors of transition-metal or rare-metal--are
not only expensive, but are also potential environmental hazards.
In addition, the correlated color temperature (CCT) of a white
light-emitting device often varies across the surface of the device
due to the non-uniformity accumulation and/or distribution of the
phosphor materials across the LED chip, therefore deteriorates the
light extraction efficiency and produces undesirable color
rendering property for light emitting devices.
[0004] In view of the foregoing, there exists in the related art a
need for an improved white LED and a method producing the same by
utilizing a novel material to convert wavelengths.
SUMMARY
[0005] The following presents a simplified summary of the
disclosure in order to provide a basic understanding to the reader.
This summary is not an extensive overview of the disclosure and it
does not identify key/critical elements of the present invention or
delineate the scope of the present invention. Its sole purpose is
to present some concepts disclosed herein in a simplified form as a
prelude to the more detailed description that is presented
later.
[0006] As embodied and broadly described herein, the present
disclosure aims to provide an improved white light-emitting diode
(LED) package structure, and a method for manufacturing the same by
employing gold nanoclusters as a wavelength-convertible material,
so that the thus produced LED can emit a desired wavelength with a
desired CCT.
[0007] In one aspect, the present disclosure is directed to a LED
package structure. According to various embodiments of the present
disclosure, the LED package structure comprises a substrate, and a
light-emitting unit disposed on the substrate. The light-emitting
unit comprises in its structure, a gallium nitride-based
semiconductor, and a polymeric layer encapsulating the gallium
nitride-based semiconductor. The polymeric layer comprises a resin
and at least one composite fluorescent gold nanocluster dispersed
therein. Each composite fluorescent gold nanocluster comprises a
gold nanocluster, and a capping layer encapsulating at least a
portion of the outer surface of the gold nanocluster. The capping
layer is composed of a matrix made of a benzene-based compound, and
a plurality of phosphine-based compounds distributed across the
matrix.
[0008] In some optional embodiments, the gallium nitride-based
semiconductor is configured to emit a light having a wavelength
ranging from 395 nm to 495 nm.
[0009] In some optional embodiments, the gallium nitride-based
semiconductor is configured to emit a light having a wavelength
that is shorter than 395 nm. In such case, the polymeric layer
further comprises a plurality of luminescent carbon nanoparticle
dispersed in the resin and may respectively emit a light having a
wavelength ranging from 400 nm to 500 nm.
[0010] According to embodiments of the present disclosure, the
benzene-based compound is selected from the group consisting of,
benzene, alkylbenzene, halobenzene, phenol, benzoic acid,
acetophenone, methyl benzoate, anisole, aniline, nitrobenzene,
benzonitrile, benzamide, benzenesulfonic acid, naphthalene, and
anthracene. For instance, the alkylbenzene may be toluene, cumene,
ethylbenzene, styrene, or xylene; and the halobenzene may be
fluorobenzene, chlorobenzene, bromobenzene, or iodobenzene.
According to certain examples of the present disclosure, the
benzene-based compound is toluene.
[0011] According to embodiments of the present disclosure, the
plurality of phosphine-based compounds is selected from the group
consisting of, phosphine, phosphine oxide, phosphonium,
diphosphine, triphosphine, alkyl phosphine, cycloalkyl phosphine,
aryl phosphine, aryl phosphine oxide, phenyl phosphine, bidentate
phosphine, silicone derivative of phosphine, siloxane or polysilane
derivative of phosphine, and olefinic phosphine. In certain
examples, the phosphine-based compound is alkyl phosphine, such as
trioctylphosphine (TOP). In certain examples, the phosphine-based
compound is aryl phosphine oxide, such as trioctylphosphine oxide
(TOPO). In alternative examples, the phosphine-based compound is
phenyl phosphine, such as triphenylphosphine (TPP).
[0012] In another aspect, the present disclosure pertains to a
method for producing the LED package structure. The present method
comprises: (a) providing a substrate; (b) electrically connecting a
gallium-nitride based semiconductor onto the substrate; (c)
overlaying the gallium nitride-based semiconductor with a slurry
comprising a resin and a plurality of composite fluorescent gold
nanoclusters; and (d) curing the slurry overlaid on the
gallium-based semiconductor for a sufficient time to form a
solidified polymeric layer, thereby creates the LED package
structure. In addition, each composite fluorescent gold nanocluster
comprises a gold nanocluster, and a capping layer encapsulating at
least a portion of an outer surface of the gold nanocluster. The
capping layer is composed of a matrix made of a benzene-based
compound, and a plurality of phosphine-based compounds distributed
across the matrix.
[0013] In some optional embodiments, the gallium nitride-based
semiconductor is configured to emit a light having a wavelength
ranging from 395 nm to 495 nm.
[0014] In some optional embodiments, the gallium nitride-based
semiconductor is configured to emit a light having a wavelength
that is shorter than 395 nm. In these embodiments, the slurry in
the step (c) further comprises a plurality of luminescent carbon
nanoparticles, which are dispersed in the resin and emit a light of
a wavelength ranging from 400 nm to 500 nm.
[0015] According to embodiments of the present disclosure, the
benzene-based compound is selected from the group consisting of
benzene, alkylbenzene, halobenzene, phenol, benzoic acid,
acetophenone, methyl benzoate, anisole, aniline, nitrobenzene,
benzonitrile, benzamide, benzenesulfonic acid, naphthalene, and
anthracene.
[0016] Preferably, the alkylbenzene is toluene, cumene,
ethylbenzene, styrene, or xylene; and the halobenzene is
fluorobenzene, chlorobenzene, bromobenzene, or iodobenzene.
According to certain working examples of the present disclosure,
the benzene-based compound is toluene.
[0017] According to embodiments of the present disclosure, the
plurality of phosphine-based compounds is selected from the group
consisting of phosphine, phosphine oxide, phosphonium, diphosphine,
triphosphine, alkyl phosphine, cycloalkyl phosphine, aryl
phosphine, aryl phosphine oxide, phenyl phosphine, bidentate
phosphine, silicone derivative of phosphine, siloxane or polysilane
derivative of phosphine, and olefinic phosphine. In certain
examples, the phosphine-based compound is aryl phosphine oxide,
such as trioctylphosphine oxide (TOPO). In certain examples, the
phosphine-based compound is alkyl phosphine, such as
trioctylphosphine (TOP). Alternatively, the phosphine-based
compound is phenyl phosphine, such as triphenylphosphine (TPP).
[0018] By virtue of the above configuration, the thus-produced LED
package structure comprises a light-emitting unit, which has
wavelength-convertible composite fluorescent gold nanoclusters
evenly distributed therein. As could be appreciated, the
fluorescence intensity and color temperature of the present LED may
vary with the concentration and volume of the present composite
fluorescent gold nanoclusters.
[0019] Furthermore, the present method is characterized in not
using any reducing agent(s) in the process of manufacturing the
present composite fluorescent gold nanocluster; accordingly, the
present LED package structure is free from any toxicity that might
be caused by or associated with the reducing agent(s), thereby
confers the safety of the present LED package structure.
[0020] Many of the attendant features and advantages of the present
disclosure will becomes better understood with reference to the
following detailed description considered in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The present description will be better understood from the
following detailed description read in light of the accompanying
drawings, where:
[0022] FIG. 1A is a cross-section view of an exemplary LED package
structure 100 according to one embodiment of the present
disclosure; and FIG. 1B is a schematic diagram illustrating a
composite fluorescent gold nanocluster 110 in FIG. 1A;
[0023] FIG. 2 is a cross-section view of an exemplary LED package
structure 200 according to another embodiment of the present
disclosure;
[0024] FIG. 3 provides a fluorescence spectrum of the composite
fluorescent gold nanoclusters encapsulated in a macromolecular
solution according to one example;
[0025] FIGS. 4A-4B respectively provide a fluorescence spectrum and
the emission properties (CCT and light rendering) of the LED
package structure according to one example;
[0026] FIGS. 5A-5B respectively provide a fluorescence spectrum and
the emission properties (CCT and light rendering) of the LED
package structure according to one example;
[0027] FIGS. 6A-6B respectively provide a fluorescence spectrum and
the emission properties (CCT and light rendering) of the LED
package structure according to one example;
[0028] FIG. 7 is fluorescent spectra showing the comparison among
the present LED package structures and the conventional one;
[0029] FIG. 8 provides a fluorescence spectrum of the luminescent
carbon nanoparticles encapsulated in a macromolecular solution
according to one example; and
[0030] FIG. 9 provides a fluorescence spectrum of the LED package
structure according to one example.
[0031] In accordance with common practice, the various described
features/elements are not drawn to scale but instead are drawn to
best illustrate specific features/elements relevant to the present
invention. Also, like reference numerals and designations in the
various drawings are used to indicate like elements/parts.
DETAILED DESCRIPTION OF THE INVENTION
[0032] The detailed description provided below in connection with
the appended drawings is intended as a description of the present
examples and is not intended to represent the only forms in which
the present example may be constructed or utilized. The description
sets forth the functions of the example and the sequence of steps
for constructing and operating the example. However, the same or
equivalent functions and sequences may be accomplished by different
examples.
I. Definition
[0033] For convenience, certain terms employed in the
specification, examples and appended claims are collected here.
Unless otherwise defined herein, scientific, and technical
terminologies employed in the present disclosure shall have the
meanings that are commonly understood and used by one of ordinary
skill in the art. Also, unless otherwise required by context, it
will be understood that singular terms shall include plural forms
of the same and plural terms shall include the singular.
Specifically, as used herein and in the claims, the singular forms
"a" and "an" include the plural reference unless the context
clearly indicates otherwise. Also, as used herein and in the
claims, the terms "at least one" and "one or more" have the same
meaning and include one, two, three, or more.
[0034] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the invention are approximations,
the numerical values set forth in the specific examples are
reported as precisely as possible. Any numerical value, however,
inherently contains certain errors necessarily resulting from the
standard deviation found in the respective testing measurements.
Also, as used herein, the term "about" generally means within 10%,
5%, 1%, or 0.5% of a given value or range. Alternatively, the term
"about" means within an acceptable standard error of the mean when
considered by one of ordinary skill in the art. Other than in the
operating/working examples, or unless otherwise expressly
specified, all of the numerical ranges, amounts, values and
percentages such as those for quantities of materials, durations of
times, temperatures, operating conditions, ratios of amounts, and
the likes thereof disclosed herein should be understood as modified
in all instances by the term "about". Accordingly, unless indicated
to the contrary, the numerical parameters set forth in the present
disclosure and attached claims are approximations that can vary as
desired. At the very least, each numerical parameter should at
least be construed in light of the number of reported significant
digits and by applying ordinary rounding techniques.
[0035] The term "wavelength-convertible" used herein refers to the
ability of a certain material to absorb wavelengths of one emission
color and convert it to a different wavelength of another emission
color, and thereby generate a desired emission color.
[0036] The term "nanoclusters" used herein refers to a collection
of small numbers (e.g., 2 to hundreds of atoms) of noble metal
atoms (e.g., gold or silver atoms) with physical sizes close to the
Fermi wavelength of an electron. Generally, nanoclusters (such as
gold nanoclusters in the present disclosure) may have diameters in
the range of about 0.1 to about 3 nm. Nanoclusters used in the
present disclosure are fluorescent gold nanoclusters, which
indicates the ability to emit light of a wavelength (emission
wavelength) when exposed to light of another wavelength (excitation
wavelength).
[0037] The term "fluorescence" or "fluorescent," as used herein,
refers to a physical phenomenon based upon the ability of certain
compounds to absorb and emit light at different wavelengths. The
absorption of light (photons) at a first wavelength is followed by
the emission of photons at a second wavelength and different
energy. As used herein, the term "shift" refers to the shifting of
the point of maximum amplitude of one or more peaks in a
fluorescence emission profile to a longer wavelength. A shift may
occur in any part of the electromagnetic spectrum.
[0038] The term "phosphine-based compound" used herein refers to a
chemical compound that has at least one phosphine group (e.g., in
the form of phosphine, phosphine oxide, phosphonium, or
phenylphosphine). The phosphine-based compounds include primary
phosphines, secondary phosphines, and tertiary phosphines, as those
known to person having ordinary skill in the art. These
phosphine-based compounds share same chemical properties, such as
an intense penetrating odor and high oxidation ability.
II. Description of the Invention
[0039] This invention aims at providing an improved LED with
excellent color rendering property and desired color temperature.
Further, as yttrium-aluminum-garnet (YAG) fluorescent materials--a
main material commonly used in manufacturing wavelength-converting
phosphors of LEDs--are cytotoxic and may cause environmental
pollution, thus the present invention also aims at providing an
improved LED, in which a novel wavelength-convertible material made
by gold nanoclusters is employed to address the above issues of YAG
fluorescent materials.
[0040] Accordingly, the first aspect of the present disclosure is
directed to a LED package structure, especially a white LED package
structure. References are made to FIGS. 1A and 1B.
[0041] Referring to FIG. 1A, which is a cross-section view of an
exemplary LED package structure according to one embodiment of the
present disclosure. The LED package structure 100 comprises a
substrate 102, and a light-emitting unit 104 constructed on the
substrate 102. To this purpose, a substrate having pre-deposited
layers of materials (e.g., nitride or oxides) commonly used in LED
industry (e.g., aluminum oxide substrate and the like) may be used
for constructing the present LED package structure. Accordingly, a
recessed portion 1022, a positive metal terminal 1024 (serving as a
positive electrode), and a negative metal terminal 1026 (serving as
a negative electrode) were respectively created on the substrate
102 via any method known in the art (e.g., photoresist etching). A
gallium nitride-based semiconductor 1042 having a p-type electrode
and an n-type electrode is then disposed in the recessed portion
1022 and on top of the positive metal terminal 1024. The p-type and
n-type electrodes (not depicted in FIG. 1A) of the gallium
nitride-based semiconductor 1042 are electrically connected to the
positive metal terminal 1024 and the negative metal terminal 1026,
respectively, by two conductive wires 1044. In some embodiments,
the gallium nitride-based semiconductor 1042 may include a material
selected from the group consisting of indium gallium nitride
(InGaN), gallium nitride (GaN), aluminum gallium nitride (AlGaN),
and a combination thereof. It should be noted that the gallium
nitride-based semiconductor 1042 illustratively depicted in FIG. 1A
is exemplified as a chip type, but is not limited thereto.
[0042] Next, a slurry comprises a resin and at least one composite
fluorescent gold nanocluster 110 is poured into the recessed
portion 1022 of the substrate 102 until the gallium nitride-based
semiconductor 1042 is completely submerged therein, after curing,
the slurry is solidified and forms a polymeric layer 1046 that
encapsulates the gallium nitride-based semiconductor 1042 therein,
thereby creates a light emitting unit 104. In some embodiments, the
slurry is a mixture of resins, preferably light-curable resins; and
a plurality of composite fluorescent gold nanoclusters 110.
According to embodiments of the present disclosure, the composite
fluorescent gold nanoclusters 110 are suspended in a macromolecular
solution, then are mixed with the resin in a volume ratio from 1:1
to 1:32, preferably is 1:1. After curing the slurry, the plurality
of composite fluorescent gold nanoclusters 110 are spread and
dispersed in the resin, therefore forming a solidified polymeric
layer 1046, as illustrated in FIG. 1A.
[0043] Examples of the light-curable resin include, but are not
limited to, 1-hydroxycyclohexyl phenyl ketone;
2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone;
2-hydroxy-2-methylpropiophenone (HMPP); 2,4,6-trimethylbenzoyl
diphenylphosphine oxide (Lucirin.RTM. TPO); 50-50 Blend of HMPP and
TPO; 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MMMP);
2,2-dimethoxy-2-phenyl acetophenone (BDK); or 1-hydroxy-2-butanone.
In some embodiments of the present disclosure, the light-curable
resin is HMPP.
[0044] The macromolecular solution is a gel or slurry phase formed
by dissolving a polymer in a proper solvent (e.g., water, alcohols,
and the like). Examples of polymers include, but is not limited to,
poly(ethylene glycol) diacrylate (PEGDA); poly(ethylene glycol)
dimethacrylate; polyvinylpyrrolidone (PVP), which generally refers
to a polymer containing vinyl pyrrolidone (also referred to as
N-vinylpyrrolidone, N-vinyl-2-pyrrolidione and
N-vinyl-2-pyrrolidinone) as a monomeric unit; poly(N-isopropyl
acrylamide); polyvinylalcohol (PVA); and polyepoxysuccinic acid
(PESA) and its salt derivatives. In some embodiments, the
macromolecular solution is a PEGDA solution (i.e., PEGDA in
water).
[0045] Referring to FIG. 1B, which is a schematic view of a
composite fluorescent gold nanocluster 110 according to one
embodiment of the present disclosure. As illustrated, the composite
fluorescent gold nanocluster 110 comprises a gold nanocluster 1110
and a capping layer 1120.
[0046] Specifically, the gold nanocluster 1110 is composed by
multiple gold atoms 1110'. As could be appreciated, although the
gold nanocluster 1110 in FIG. 1B is depicted to compose of a
specific number of gold atoms 1110', yet embodiments of the present
invention are not limited thereto; rather, the gold nanocluster
1110 may be an aggregation of any suitable number in the range of
several to dozens of gold atoms 1110'. Preferably, the gold
nanoclusters 1110 as described herein comprise 2, 3, 4, 5, 6, 7, 8,
9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42,
43, 44, 45, 46, 47, 48, 49, or 50 atoms. In other preferred
embodiments, the gold nanoclusters 1110 comprise 2-30 atoms, 5-25
atoms, 5-20 atoms, or 5-15 atoms. Generally, the diameter of the
gold nanocluster 1110 is about 0.1 to about 3 nm; preferably less
than about 2 nm.
[0047] Still referring to FIG. 1B, the capping layer 1120 comprises
a matrix 1122 made of a benzene-based compound; and a plurality of
phosphine-based compounds 1124 distributed across the matrix 1122.
As illustrated in FIG. 1B, the capping layer 1120 encapsulates the
entire gold nanocluster 1110. In other alternative embodiments, the
capping layer 1120 encapsulates or covers just a portion of the
outer surface of the gold nanocluster 1110, or several portions of
the outer surface of the gold nanocluster 1110.
[0048] According to one embodiment of the present disclosure, the
composite fluorescent gold nanoclusters 110 of the present
disclosure may be produced by various methods. Each methods
preferably comprises at least the following steps: (a) mixing
gold(III) chloride (AuCl.sub.3) and a benzene-based compound at a
molar ratio of about 1:0.5 to 1:5 to produce a first fluorescent
gold nanoclusters; (b) treating the first fluorescent gold
nanoclusters with an energy source selected from the group
consisting of UV, acoustic, heat, microwave and a combination
thereof to produce a second fluorescent gold nanoclusters; and (c)
modifying the second fluorescent gold nanoclusters of the step (b)
with a phosphine-based compound to produce the composite
fluorescent gold nanoclusters of the present disclosure. It is
worth noting that no reducing agent is required in this preferable
method.
[0049] Examples of the benzene-based compound include, but are not
limited to, benzene, alkylbenzene (such as, toluene, cumene,
ethylbenzene, styrene, and xylene), halobenzene (e.g.,
fluorobenzene, chlorobenzene, bromobenzene, and iodobenzene),
oxygen-containing benzene (e.g., phenol, benzoic acid,
acetophenone, methyl benzoate, and anisole), nitrogen-containing
benzene (e.g., aniline, nitrobenzene, benzonitrile, and benzamide),
sulfur-containing benzene (e.g., benzenesulfonic acid), or
polyaromatic (e.g., naphthalene, and anthracene). According to some
examples, the benzene-based compound is toluene.
[0050] In addition, phosphine-based compound is known to person
having ordinary skill in the art, suitable examples of
phosphine-based compound include, but are not limited to,
phosphine, phosphine oxide, phosphonium, diphosphine, triphosphine,
alkyl phosphine, cycloalkyl phosphine, aryl phosphine, aryl
phosphine oxide, phenyl phosphine, bidentate phosphine, silicone
derivative of phosphine, siloxane or polysilane derivative of
phosphine, and olefinic phosphine. In some examples, the
phosphine-based compound is alkyl phosphine, such as
trioctylphosphine (TOP). In other examples, the phosphine-based
compound is aryl phosphine oxide such as trioctylphosphine oxide
(TOPO). In still other examples, the phosphine-based compound is
phenyl phosphine, such as triphenylphosphine (TPP).
[0051] According to the present disclosure, the light-emitting unit
104 of the LED package structure 100 is configured to emit lights
with pre-determined wavelengths depending on doping materials
contained therein. The composite fluorescent gold nanoclusters 110
are configured to emit a first light in a first wavelength, and to
absorb at least a portion of the light emitted from the gallium
nitride-based semiconductor 1042, and emits a second light in a
second wavelength, in which the first and second wavelengths are
different. Eventually, the un-absorbed light emitted from the
gallium nitride-based semiconductors 1042 and the second light
emitted by the composite fluorescent gold nanoclusters 110 would
combine with each other to produce a desired light color (e.g.,
white light).
[0052] More specifically, according to certain embodiments of the
present disclosure, the original wavelength of the composite
fluorescent gold nanocluster 110 is between about 500 nm to about
590 nm, such as 500, 505, 510, 515, 520, 525, 530, 535, 540, 545,
550, 555, 560, 565, 570, 575, 580, 585, and 590 nm. As the
converted wavelength of the second light after excited by the
light-emitting unit 104, the converted wavelength of the peak
emission is between about 550 nm to about 680 nm, such as 550, 555,
560, 565, 570, 575, 580, 585, 590, 595, 600, 605, 610, 615, 620,
625, 630, 635, 640, 645, 650, 655, 660, 665, 670, 675, and 680 nm.
In some practical examples, the second peak emission is at about
550 nm to 600 nm. In other practical examples, the wavelength of
the second peak emission is at about 600 to 675 nm (i.e., orange
and/or red lights).
[0053] According to one embodiment of the present disclosure, in
the LED package structure 100, the gallium nitride-based
semiconductors 1042 of the light-emitted unit 104 is InGaN/GaN
semiconductors that emits a light having a wavelength between 395
nm to 495 nm (a.k.a., a blue light). In such case, the composite
fluorescent gold nanoclusters 110 convert the emission light from
the original wavelength between 570 nm to 590 nm to a wavelength
between 600 nm to 675 nm by absorbing the blue light emitted from
the gallium nitride-based semiconductors 1042. Therefore, the LED
package structure 100 eventually emits a white light as a result of
color addition of the original blue light emitted from the gallium
nitride-based semiconductors 1042, and the first light and the
re-emitted second light respectively generated from the composite
fluorescent gold nanoclusters 110 before and after wavelength
conversion.
[0054] Referring to FIG. 2, which is a schematic drawing of an LED
package structure 200 in according to another embodiment of the
present disclosure. The LED package structure 200 emits a white
light, and is characterized in having the composite fluorescent
gold nanoclusters 210 as the wavelength-convertible materials. The
configuration of the LED package structure 200 is similar to that
of the LED package structure 100, and is constructed in similar
manner except a GaN/AlGaN semiconductor emitting a wavelength
shorter than 395 nm is used, and the polymeric layer encapsulating
the GaN/AlGaN semiconductor further comprises a plurality of
luminescent carbon nanoparticles 220 dispersed in the resin. As
depicted, the LED package structure 200 comprise in its structure,
a substrate 202; and a light emitting unit 204, which comprises a
GaN/AlGaN semiconductor 2042 and a polymeric layer 2046
encapsulating the GaN/AlGaN semiconductor 2042. Similar to the
process described above for constructing the LED package structure
100 of FIG. 1A, a positive metal terminal 2024 and a negative metal
terminal 2026 respectively serving as the positive and negative
electrodes are constructed on the substrate 202; then, the
GaN/AlGaN semiconductor 2042 is disposed in a recessed portion 2022
of the substrate 202, and on top of the positive metal terminal
2024; the GaN/AlGaN semiconductor 2042 is electronically connected
to the positive and negative metal terminals 2024, 2026 via two
conductive wires 2044. A polymeric layer 2046 encapsulating the
GaN/AlGaN semiconductor 2042 therein is formed in the recessed
portion 2022 thereby creating the light emitting unit 204. The
GaN/AlGaN semiconductor emits a wavelength shorter than 395 nm,
preferably in the range from about 200 nm to 395 nm. In other
words, the GaN/AlGaN semiconductor emits an ultraviolet (UV) light.
In addition to the resin and the plurality of composite fluorescent
gold nanoclusters 210, the polymeric layer 2046 in this embodiment
further comprises a plurality of luminescent carbon nanoparticles
220 dispersed in the resin. In practice, the polymeric layer 2046
is formed by filling the recessed portion 2022 of the substrate 202
with a slurry mixture of light-curable resins, at least one
composite fluorescent gold nanoclusters 210 and a plurality of
luminescent carbon nanoparticles 220. In some embodiment, the
composite fluorescent gold nanoclusters and the luminescent carbon
nanoparticles are mixed in a volume ratio of 1:10 to 10:1,
preferably, 1:1. After curing (e.g., by heat or by exposed to
light), the slurry mixture is solidified into the polymeric layer
2046, with the composite fluorescent gold nanoclusters 210 and the
luminescent carbon nanoparticles 220 dispersed in the resin, as
illustrated in FIG. 2.
[0055] The luminescent carbon nanoparticles 220 can be commercially
available or can be synthesized at the bench in accordance with any
method known in the art. According to the present disclosure, the
luminescent carbon nanoparticles 220 are exemplary produced from
carbon sources such as a mixture of carboxylic acids and long-chain
hydrocarbon alkenes but may be varied according to practical needs.
In some embodiments of the present disclosure, the carboxylic acid
is citric acid and the long-chain hydrocarbon alkene is octadecene.
Generally, the diameter of the luminescent carbon nanoparticle 220
is about 0.1 to about 3 nm; preferably is about 2.5 to 2.8 nm.
[0056] More specifically, the GaN/AlGaN semiconductor emits a
wavelength shorter than 395 nm; and the luminescent carbon
nanoparticles 220 respectively emit a blue light having a
wavelength ranging from 400 nm to 500 nm. As such, by absorbing a
portion of UV light, the original emission wavelength of the
composite fluorescent gold nanoclusters 210 is converted from about
500-590 nm to about 550 nm to 600 nm. By this configuration, the
LED package structure 200 eventually emits a white light, which is
the summation of blue light and yellow light respectively emitted
from the plurality of luminescent carbon nanoparticles 220 and the
composite fluorescent gold nanoclusters 210 dispersed in the
polymeric layer 2046.
[0057] It should be noted that the LED package structures of the
present disclosure provide improved light-emitting properties due
to the composite fluorescent gold nanoclusters, which possess at
least following advantages: (1) the surface modification with
phosphine-based compounds for the composite fluorescent gold
nanoclusters increase the solubility thereof in the macromolecular
solution, allowing the composite fluorescent gold nanoclusters to
disperse more uniformly in the slurry; (2) since the fluorescence
intensity of the wavelength-convertible materials is stable, the
present LED package structure has excellent white color rendering
property; (3) the fluorescence intensity of the composite
fluorescent gold nanoclusters also increases in a correlation with
the level of concentration thereof because of modification with
benzene-based and phosphine-based compounds; and (4) the present
fluorescent gold nanocluster are biocompatible and free from any
toxicity since the manufacturing process of which does not require
the use of any reducing agent, thereby enhancing the safety usage
of the present LED package structures.
[0058] The following Examples are provided to elucidate certain
aspects of the present invention and to aid those of skilled in the
art in practicing this invention. These Examples are in no way to
be considered to limit the scope of the invention in any manner.
Without further elaboration, it is believed that one skilled in the
art can, based on the description herein, utilize the present
invention to its fullest extent. All publications cited herein are
hereby incorporated by reference in their entirety.
Example
1. Manufacturing White LED Package Structure
1.1 Preparation of Composite Fluorescent Gold Nanoclusters
[0059] In an oxygen-free and moisture-free glovebox, mixed gold
(III) chloride (AuCl.sub.3) with toluene in the amount of
approximately 7.5 mg/mL. The mixture was shaken for about 5 minutes
to facilitate mixing, then heated at 80.degree. C. or 120.degree.
C. for 1 hour. Then, the mixture was centrifuged at 3,000 rpm for 5
minutes, the supernatant was collected and exposed to UV radiation
for 24 hours. Next, the UV-radiated supernatant (containing
AuCl.sub.3 in a concentration of 1 mg/mL) was mixed with a toluene
solution containing phosphine-based compound, e.g., TOP (200 mM),
the thus produced composite fluorescent gold nanoclusters in
toluene was stored as a stock until further use. For the sake of
brevity, the composite fluorescent gold nanoclusters encompassing
TOP is abbreviated as CFGN-TOPs hereinafter. In this experiment,
the primary concentration of the CFGN-TOPs in the stock is defined
as a stock concentration, which is denoted by 1-fold or
1.times..
1.2 Preparation of Luminescent Carbon Nanoparticles
[0060] Citric acid (0.8 g) and glycine (0.2 g) were respectively
added into a nitric acid solution (which was prepared by mixing 1
mL nitric acid (0.5M) with 1 mL H.sub.2O), the mixture was then
subjected to ultrasonic oscillation until all matters were
completely dissolved. The thus produced solution was added into an
oil solution (oleylamine (3 ml) and octadecene (7 ml)), and the
mixture was ultrasonic oscillated for 15 seconds to form milky
micelles, and continued to stir (at 700 rpm) for 10 minutes. The
product was heated at 200.degree. C. for 30 minutes in the presence
of argon, then was centrifuged (3,000 rpm, 5 minutes) to remove
carbon nanoparticles that were lower 1 nm in size. The remaining
carbon nanoparticles were re-dissolved in acetone in a volume ratio
of 1:3, then centrifuged at the speed of 13,300 rpm for 10 minutes.
The carbon particles were harvested and re-suspended in toluene and
stored as a stock. The thus produced concentration of the
luminescent carbon nanoparticles is defined as a stock
concentration, which is denoted by 1.times..
1.3 Encapsulating the Blue Light-Emitting Chip with a Polymer
Containing Composite Fluorescent Gold Nanoclusters Obtained from
Example 1.1
[0061] The toluene solution contacting composite fluorescent gold
nanoclusters (CFGN-TOPs) obtained from Example 1.1 were dried by an
evaporator. The composite fluorescent gold nanoclusters were
re-suspended in a slurry of light-curable resin (HMPP) and PEGDA
polymer in a pre-determined concentration (i.e., 0.59.times. to
1.times.) or volume (i.e., 10-30 .mu.L). The slurry was overlaid
onto a substrate where a blue color light-emitting chip disposed,
the slurry was cured for 60-90 seconds to form a solidified
polymeric layer encapsulating the blue color light-emitting chip
therein thereby producing the desired white light LED package
structure.
1.4 Encapsulating the UV Light-Emitting Chip with a Polymer
Containing the Composite Fluorescent Gold Nanoclusters of Example
1.1 and the Luminescent Carbon Nanoparticles of Example 1.2
[0062] The composite fluorescent gold nanoclusters of Example 1.1
and the luminescent carbon nanoparticles of Example 1.2 were mix in
a volume ratio of 1:10 to 10:1 and were dried by an evaporator,
then were re-suspended in a slurry of light-curable resin (HMPP)
and PEGDA polymer in a determined concentration or volume (e.g., in
a volume ratio of 1:1). The slurry was overlaid onto a substrate
where a UV light-emitting chip was disposed, the slurry was cured
for 60-90 seconds to form a solidified polymeric layer
encapsulating the UV light-emitting chip therein thereby producing
the desired white light LED package structure.
2. Characterization of the White Light LED Package Structure of
Example 1
[0063] The function of the white light LED package structure (i.e.,
the light-emitting property) was evaluated by the degree of
dispersion of composite fluorescent gold nanoclusters in
macromolecular solution, the amount of phosphine-based compound in
the composite fluorescent gold nanoclusters.
2.1 Dispersion Characteristics of Gold Nanoclusters in
Macromolecular Solution
[0064] To verify the dispersibility, different condensed
concentrations (1.6.times. and 3.33.times.) of the stock composite
fluorescent gold nanoclusters in macromolecular solutions were
mixed with PEGDA solution, and fluorescence intensity emitted
thereform was measured. It was found that the composite fluorescent
gold nanoclusters distributed uniformly across the PEGDA film
regardless concentrations thereof; in addition, when excited with a
light of 350 nm, the peak emission of the CFGN-TOPs was found to be
centralized at about 550-575 nm (FIG. 3). These results indicated
that the dispersibility of the present composite fluorescent gold
nanoclusters is high and desirable.
2.2 Light Performance of White LED Package Structure of Example 1.3
(CFGN-TOPs)
2.2.1 Light Emission Characteristics Vs. Composite Fluorescent Gold
Nanoclusters Concentrations
[0065] Different diluted concentrations (0.59.times., 0.656.times.,
0.72.times., 0.81.times., and 1.times.) of the stock CFGN-TOPs were
encapsulated within the blue color light-emitting chip in
accordance with procedures described in Example 1.3. After
encapsulation, the LED package structure was powered by 25 mA
current and subjected to fluorescent intensity measurement using
fluorescence photoluminescence spectrophotometer. Results are
depicted in FIGS. 4A-4B.
[0066] It appeared that the fluorescent intensity increased with an
increase in the concentration of CFGN-TOPs (FIG. 4A). From a
chromaticity diagram (CIE 1931 XYZ color spaces) result, the color
emitted from the LED package structure shifted from blue color to
white color, and eventually turned into yellow color. Further, the
CCT of the light emitted by LED package structure decreased with an
increase in the concentration of CFGN-TOPs. The CCT of the LED
package structure was 5751K when the LED package structure emits a
white light. On the other hand, the light rendering (Ra) of the LED
package structure reached the peak of 92.71 Ra (FIG. 4B).
2.2.2 Light Emission Characteristics Vs. Composite Fluorescent Gold
Nanoclusters Volumes
[0067] Different volumes of the CFGN-TOPs (10-30 .mu.l) were
encapsulated within the blue color light-emitting chip in
accordance with procedures described in Example 1.3. After
encapsulation, the LED package structure was powered by 25 mA
current and subjected to fluorescent intensity measurement using
fluorescence photoluminescence spectrophotometer. Results are
depicted in FIGS. 5A-5B. The emission profile of FIG. 5A indicated
that the fluorescent intensity increased with an increase in the
volume of CFGN-TOPs. As the CCT of the light emitted from LED
package structure, it decreased with an increase in the volume of
CFGN-TOPs. The CCT of the LED package structure was about 3993K
when the LED package structure emitted a white light. On the other
hand, the light rendering (Ra) of the LED package structure did not
changed significantly with a change in the volume, and reached the
highest performance at 90.17 Ra (FIG. 5B).
2.2.3 Light Emission Characteristics Vs. Electric Currents
[0068] 1.times. stock concentration of CFGN-TOPs (20 .mu.l) were
encapsulated within the blue color light-emitting chip in
accordance with steps described in Example 1.3. After
encapsulation, the LED package structure was powered by a current
in the range of 5-30 mA and was subjected to fluorescent intensity
measurement using fluorescence photoluminescence spectrophotometer.
Results are depicted in FIGS. 6A-6B. The emission profile of FIG.
6A revealed that the fluorescent intensity increased with an
increase in the current density, whereas the CCT of the light
emitted from LED package structure and the light rendering (Ra)
thereof remained relatively unchanged (FIG. 6B). CCT of the LED
package structure was around 5200K, and the light rendering
remained about 90.
2.3 Comparison of Light Performances Among LED Package Structures
Respectively Comprising Phosphors and the Present Composite
Fluorescent Gold Nanoclusters of Example 1.3
[0069] Light performance of the present white LED package
structures (in which the wavelength-convertible material was
CFGN-TOPs) was compared with that of a conventional LED package
structure, in which the wavelength-convertible material was
phosphor Ce.sup.3+-doped Y.sub.3Al.sub.5O.sub.12 (YAG:Ce.sup.3+).
The results are depicted in FIG. 7 and are summarized in Table 1.
It was found that the fluorescent intensities emitted from the
present wavelength-convertible materials are relatively stronger as
compared with that of a LED package structure comprising phosphors.
Further, the white LED package structures of the present disclosure
possessed greater light rendering property (Ra) than that of a
conventional LED package structure in which phosphor materials were
used.
TABLE-US-00001 TABLE 1 Comparison between devices respectively
comprising CFGN-TOPs and conventional YAG: Ce.sup.3+ Wavelength-
Chromaticity diagmm (CIE LED package convertible 1931 coordinates)
structures material x-axis y-axis CCT (K) Ra Conventional LED YAG:
Ce.sup.3+ 0.31207 0.30866 6728 77.1026 Present LED CFGN-TOPs 0.3397
0.32548 5143 91.7027
2.4 Dispersion Characteristics of Luminescent Carbon Nanoparticles
in Macromolecular Solution
[0070] Like Example 2.1, to verify the dispersibility, different
concentrations (0.5.times., 1.times. and 2.times.) of the stock
luminescent carbon nanoparticles in macromolecular solutions were
mixed with PEGDA solution, and fluorescence intensity emitted
thereform was measured. It can be observed that the luminescent
carbon nanoparticles distribute uniformly across the PEGDA film
regardless concentrations thereof; in addition, when emitted by a
350 nm wavelength, the peak emission of the luminescent carbon
nanoparticles is centralized about 450 nm (FIG. 8). These results
indicated that the uniformity of the distributed luminescent carbon
nanoparticles is high and desirable.
2.5 Light Performance of White LED Package Structure of Example 1.4
(CFGN-TOP)
[0071] The CFGN-TOPs of Example 1.1 and the luminescent carbon
nanoparticles obtained from Example 1.2 were mix in a ratio of 1:1
and were encapsulated within the UV light-emitting chip by the
method of Example 1.4. After encapsulation, the LED package
structure was powered by 25 mA current and subjected to fluorescent
intensity measurement using fluorescence photoluminescence
spectrophotometer. Results are depicted in FIG. 9. The emission
profile of FIG. 9 represents the fluorescent emission was shifted
and converted to visible spectrum, which eventually emitting as a
white light.
[0072] It will be understood that the above description of
embodiments is given by way of example only and that various
modifications may be made by those with ordinary skill in the art.
The above specification, examples and data provide a complete
description of the structure and use of exemplary embodiments of
the invention. Although various embodiments of the invention have
been described above with a certain degree of particularity, or
with reference to one or more individual embodiments, those with
ordinary skill in the art could make numerous alterations to the
disclosed embodiments without departing from the spirit or scope of
this invention.
* * * * *