TW201824579A - Compound-based solar cell and manufacturing method of light absorption layer - Google Patents

Abstract

A compound-based solar cell including a first electrode, a second electrode, a first type doped semiconductor layer and a second type doped semiconductor layer is provided. The first type doped semiconductor layer is disposed between the first electrode and the second electrode, and the second type doped semiconductor layer is disposed between the first type doped semiconductor layer and the second electrode. The first type doped semiconductor layer has a first side adjacent to the first electrode and a second side adjacent to the second type doped semiconductor layer. The first type doped semiconductor layer includes at least one of a plurality of elements, and the elements includes Potassium, Rubidium and Cesium. The concentration of at least one of the elements on the first side is higher than the concentration on the second side. Besides, a manufacturing method of a light absorption layer is also provided.

Description

Compound solar cell and light absorbing layer manufacturing method

The present disclosure relates to a solar cell, and more particularly to a compound solar cell and a method of fabricating the light absorbing layer.

After years of development, solar cells have made great progress in power conversion efficiency, stability and various performance indicators. In recent years, many high-efficiency thin film solar cells have been developed in response to the development of thinner solar cells. Thin film solar cells can be classified into many types according to material technology, such as amorphous germanium (a-Si), cadmium telluride (CdTe), copper indium selenide (CIS), copper indium gallium selenide (CIGS) thin film solar cells, and the like. The light absorbing layer of the copper indium gallium selenide thin film solar cell is a copper indium gallium selenide film. The copper indium gallium selenide thin film is a direct bandgap semiconductor material, and it can absorb light over a wide range of solar spectra, so the copper indium gallium selenide thin film solar cell has high photoelectric conversion efficiency.

In general, the light absorbing layer absorbs light energy and then excites electron hole pairs. The electron hole pair at the P/N junction (p junction) separates electrons and holes, and electrons and holes pass through the semiconductor material. It is derived and then generates current. However, in the process of deriving electrons and holes, it is easy to increase the probability of electron hole recombination due to factors such as film quality, and to reduce the photoelectric conversion efficiency of the solar cell. In order to maintain good film quality to reduce the probability of electron hole recombination, a general method for producing a copper indium gallium selenide film is to adopt a vacuum process, such as a co-evaporation method and a two-stage sequential method. Wait for the process. However, the vacuum process will make the solar cell overall manufacturing cost higher and the process time longer. Therefore, how to produce a high-quality light absorbing layer and meet the principle of low cost and rapid production is one of the goals that developers are currently trying to achieve.

The compound solar cell of the disclosed embodiment includes a first electrode, a second electrode, a first type doped semiconductor layer, and a second type doped semiconductor layer. The first type doped semiconductor layer is disposed between the first electrode and the second electrode, and the second type doped semiconductor layer is disposed between the first type doped semiconductor layer and the second electrode. The first type doped semiconductor layer has a first side adjacent to the first electrode and a second side adjacent to the second type doped semiconductor layer. The first type doped semiconductor layer includes at least one of a plurality of elements, and the elements include potassium, germanium, and antimony. At least one of the elements has a higher concentration on the first side than on the second side.

The method for fabricating the light absorbing layer of the embodiment of the present disclosure includes: forming a precursor layer on the substrate. The precursor layer includes a plurality of nano particles, and the materials of the nano particles include copper oxide, indium oxide, and gallium oxide; providing a slurry on the precursor layer, wherein the material of the slurry includes an alkali metal compound; The slurry and the precursor layer are heat treated.

The above described features and advantages of the present invention will be more apparent from the following description.

FIG. 1A to FIG. 1F are schematic diagrams showing the fabrication of a compound solar cell according to an embodiment of the present disclosure. Please refer to FIG. 1A first. In the present embodiment, first, the substrate SUB is provided, and the first electrode 110 is formed on the substrate SUB. Specifically, the first electrode 110 serves as a back electrode of the compound solar cell 100 (as shown in FIG. 1F ), which may include molybdenum, silver, aluminum, chromium (Chromium), titanium (Titanium), and nickel (Nickel). ), gold or a combination thereof. For example, the first electrode 110 may be a molybdenum electrode plated on the substrate SUB. Next, referring to FIG. 1B, a precursor layer PrL is formed on the substrate SUB. Specifically, the precursor layer PrL is formed on the first electrode 110, and the first electrode 110 is located between the substrate SUB and the precursor layer PrL. In this embodiment, the precursor layer PrL includes a plurality of nanoparticles (NPs), and the materials of the nano particles include copper oxide, indium oxide, and gallium oxide. Specifically, the precursor layer PrL is, for example, a copper indium gallium (CIG) metal precursor, which may be formed, for example, by selenization treatment, sulfurization treatment, or any combination of selenization and vulcanization. Indium gallium selenide (CIGS) film. For example, the precursor layer PrL can be formed into a copper indium gallium selenide film by a Sulfurization After Selenization (SAS) treatment, and the disclosure is not limited thereto. In addition, in the present embodiment, the method of forming the precursor layer PrL on the substrate SUB includes, for example, coating a precursor on the substrate SUB to form a precursor layer PrL. These coatings in the precursor layer PrL can maintain the morphology of the nanoparticles by coating. However, in some embodiments, the precursor layer PrL may be formed on the substrate SUB by other process methods, and the disclosure is not limited thereto.

Next, referring to FIG. 1C, a slurry 190 is provided on the precursor layer PrL, and the material of the slurry 190 includes an alkali metal compound 192. Specifically, the slurry 190 further includes a solvent 194, and the alkali metal compound 192 is uniformly dispersed in the solvent 194. In detail, the alkali metal compound 192 includes at least one of a plurality of elements 122, and these elements 122 include potassium (Potassium), rubidium, and cesium. For example, the alkali metal compound 192 of the present embodiment is Potassium fluoride (KF). In addition, the solvent 194 may include, for example, water, an alcohol solvent, an ester solvent, a ketone solvent, an ether solvent, an amine solvent, an acid solvent, a base solvent, or a combination thereof, and the alkali metal compound 192 is in the slurry 190. The weight percent concentration is, for example, falling within the range of 0.01% to 0.6%. In the present embodiment, the method of providing the slurry 190 on the precursor layer PrL comprises coating the slurry 190 by capillary coating, spin coating, brush coating, knife coating, spray coating or printing coating. On the precursor layer PrL. In particular, in some related embodiments, the selection of solvent 194, the concentration of alkali metal compound 192 in slurry 190, and the process of providing slurry 190 on precursor layer PrL can be adjusted according to actual process requirements. This disclosure is not limited to this. Further, in the present embodiment, the slurry 190 which is uniformly coated to be provided on the precursor layer PrL forms a film layer, and the thickness T of the film layer falls within the range of 3 nm to 100 nm. However, in some embodiments, the film layer of the slurry 190 applied to the precursor layer PrL may have other thicknesses according to actual process requirements, and the disclosure is not limited thereto.

Referring to FIG. 1D, after the slurry 190 is provided on the precursor layer PrL, the slurry 190 is dried to volatilize the solvent 194. Specifically, the drying treatment is, for example, moderate heating of the slurry 190 on the precursor layer PrL to promote the evaporation of the solvent 194, and the heating temperature thereof is, for example, less than or equal to 100 degrees Celsius. Alternatively, the slurry 190 on the precursor layer PrL may be allowed to stand for a period of time to allow it to air dry naturally.

Next, referring to FIG. 1E, in the present embodiment, the slurry 190 and the precursor layer PrL are subjected to heat treatment. Specifically, the heat treatment is, for example, a selenization treatment or a post-selenization vulcanization treatment. In detail, the method of performing the heat treatment of the slurry 190 and the precursor layer PrL includes: placing the slurry 190 and the precursor layer PrL in a gaseous environment, wherein the gas environment includes a gas of a group VIA element. Further, the gas atmosphere includes, for example, a gas such as air, nitrogen, hydrogen, argon, and/or ammonia, and the gas pressure of the gas atmosphere falls within a range of, for example, 10 ^-4 torr to 760 Torr. In addition to this, the temperature of the gas atmosphere is, for example, falling within a range of 300 degrees Celsius to 600 degrees Celsius, and the time for performing the heat treatment is, for example, falling within a range of 1 minute to 300 minutes. In detail, the appropriate gas environment can be set according to the actual process requirements for heat treatment, and appropriate relevant parameters are set, and the disclosure is not limited thereto.

Referring to FIG. 1E, in the embodiment, during the heat treatment, the nano particles of the precursor layer PrL will, for example, grow a copper indium gallium selenide crystal, and the copper indium gallium selenide crystal will continue to grow. Copper indium gallium selenide film. Specifically, the copper indium gallium selenide film is, for example, the light absorbing layer AL of the compound solar cell 100, and is also the first type doped semiconductor layer 120 of the solar cell 100. In some related embodiments, the first type doped semiconductor layer 120 may include, for example, a group IB element, a group IIIA element, by material selection of the nano particles of the precursor layer PrL and gas selection of a gas environment in which the heat treatment is performed. , VIA family elements or a combination thereof. Alternatively, the first type doped semiconductor layer 120 may include, for example, a group IB element, a group IIB element, a group IVA element, a group VIA element, or a combination thereof, and the disclosure is not limited thereto. In addition, in detail, in the process of crystal growth of the copper indium gallium selenide crystal of the present embodiment, the elements 122 of the alkali metal compound 192 enter the copper indium gallium selenide crystal structure and are distributed on the surface and crystal of the copper indium gallium selenide film. Among the structures and among the grain boundaries.

Referring to FIG. 1F, in the embodiment, the second type doped semiconductor layer 130, the second electrode 140, and the electrode 150 are sequentially formed on the first type doped semiconductor layer 120, thereby completing the compound solar cell 100. Production. Specifically, the compound solar cell 100 includes the above-described substrate SUB, the first electrode 110, the first type doped semiconductor layer 120, the second type doped semiconductor layer 130, the second electrode 140, and the electrode 150. The first electrode 110 is disposed between the first type doped semiconductor layer 120 and the substrate SUB. The first type doped semiconductor layer 120 is disposed between the first electrode 110 and the second electrode 140 , and the second type doped semiconductor layer 130 is disposed between the first type doped semiconductor layer 120 and the second electrode 140 . One of the first type doped semiconductor layer 120 and the second type doped semiconductor layer 130 is an N type doped semiconductor layer, and one of the first type doped semiconductor layer 120 and the second type doped semiconductor layer 130 One is a P-type doped semiconductor layer.

Specifically, the compound solar cell 100 is, for example, a copper indium gallium selenide thin film solar cell. The substrate SUB is, for example, a flexible substrate such as a stainless steel sheet or a soda-lime glass (SLG) or a non-flexible substrate. The first type doped semiconductor layer 120 is, for example, a P-type doped copper indium gallium selenide film and serves as a light absorbing layer AL, and the first electrode 110 is, for example, adapted to form an ohmic contact with a copper indium gallium selenide film. Molybdenum back electrode. In addition, the second type doped semiconductor layer 130 is, for example, a cadmium sulfide (CdS) buffer layer having an N-type doping, and the second electrode 140 is, for example, an intrinsic zinc oxide (i-) including a phase stack. The ZnO) layer 142 and the transparent conductive layer 144, and the intrinsic zinc oxide layer 142 is disposed between the transparent conductive layer 144 and the second type doped semiconductor layer 130. Specifically, the transparent conductive layer 144 is, for example, Al-doped zinc oxide (AZO) or other types of transparent conductive films, and the disclosure is not limited thereto. In addition, the electrode 150 in contact with the second electrode 140 is, for example, designed in a strip shape to avoid light shielding. In some embodiments, the compound solar cell 100 can also be other types of compound solar cells, and the disclosure is not limited thereto.

In the present embodiment, light enters the compound solar cell 100, for example, from one side of the second electrode 140. When the first type doped semiconductor layer 120, which is the light absorbing layer AL, absorbs light energy, it generates an electron hole pair. A P/N junction is formed between the first type doped semiconductor layer 120 and the second type doped semiconductor layer 130, and an electron hole pair located at the P/N junction separates electrons and holes. The electrons and the holes are respectively led out by the second type doped semiconductor layer 130 and the first type doped semiconductor layer 120, respectively, and are respectively received by the second electrode 140 and the first electrode 110, thereby generating a current.

Specifically, in the present embodiment, the first type doped semiconductor layer 120 has a first side S1 close to the first electrode 110 and a second side S2 close to the second type doped semiconductor layer 130. The first type doped semiconductor layer 120 includes at least one of a plurality of elements 122 (such as the plurality of elements 122 of the foregoing alkali metal compound 192), and these elements 122 include potassium, germanium, and antimony. For example, the alkali metal compound 192 of the present embodiment is potassium fluoride, and after heat treatment, at least a majority of fluorine is volatilized, so that the formed first type doped semiconductor layer 120 (light absorbing layer) is formed. The element 122 included in AL) is potassium, and potassium is distributed in the surface, crystal structure and grain boundaries of the copper indium gallium selenide film of the first type doped semiconductor layer 120. Specifically, since at least one of the elements 122 passes through the gap between the nano particles of the precursor layer PrL and moves downward by heat diffusion during heat treatment, at least one of the elements 122 One of them has a proper concentration distribution in the first type doped semiconductor layer 120. In detail, at least one of the elements 122 has a higher concentration on the first side S1 than on the second side S2. That is, in the present embodiment, potassium is distributed in the first type doped semiconductor layer 120 (light absorbing layer AL) at a concentration closer to the substrate SUB than from the substrate SUB. Specifically, the concentration of potassium distributed in the first type doped semiconductor layer 120 near the first side S1 of the first electrode 110 is higher than the concentration near the second side S2 of the second type doped semiconductor layer 130. In some embodiments, the precursor layer PrL may be formed on the substrate SUB by the above-described process method, and a light absorbing layer AL is formed on the substrate SUB in the same embodiment as described above, wherein the elements in the light absorbing layer AL are At least one of the 122 is at a higher concentration near the substrate SUB than at a distance away from the substrate SUB.

In the present embodiment, since the surface, crystal structure and grain boundary of the copper indium gallium selenide film of the first type doped semiconductor layer 120 have an appropriate potassium concentration distribution, the material interface (for example, the first type doped semiconductor layer 120) And the bandgap of the defect on the grain boundary of the second type doped semiconductor layer 130) or the first type doped semiconductor layer 120 may fall below the Fermi level. That is, potassium can provide a passivation effect of the material interface and grain boundaries. When the carrier passes through the above material interface or the above grain boundary, the probability of carrier recombination is reduced. In addition, in the present embodiment, in the process of heat-treating the slurry 190 and the precursor layer PrL to form the first-type doped semiconductor layer 120 (copper indium gallium selenide crystal structure), potassium will occupy the crystal first. The vacancy of copper in the grid. When cadmium sulfide (second-type doped semiconductor layer 130) is deposited on the copper indium gallium selenide crystal structure by deposition, cadmium also occupies copper vacancies. At this point, the potassium that originally occupied the copper vacancies will leave, creating more vacancies for copper that can be occupied by cadmium. Therefore, more cadmium can occupy the copper vacancy, so that the P/N junction between the surface of the copper indium gallium selenide crystal film and the cadmium sulfide can achieve a better energy level matching. In the present embodiment, the compound solar cell 100 can have a high open circuit voltage (non-vacuum process) based on factors such as a decrease in carrier composite probability and improved P/N junction energy level matching. V _oc ) and fill factor (FF), which in turn has better power conversion efficiency (PCE).

2 is a graph showing the element content of the light absorbing layer of the compound solar cell of the embodiment of FIG. 1F at different depths, please refer to FIG. 2 . The vertical axis of FIG. 2 represents the magnitude of the signal intensity for determining the element content of the compound solar cell 100, and the unit is count/second, and the horizontal axis represents the depth at which the compound solar cell 100 is calculated from the second electrode 140 and extends toward the first electrode 110. The unit is nanometer. The depth range defined between the two dashed lines in FIG. 2 indicates the depth range in which the first type doped semiconductor layer 120 is located. In addition, "S", "Se", "Ga", "In", "Cu", "Na", and "K" indicated in Fig. 2 indicate sulfur, selenium, gallium, indium, copper, sodium, and potassium, respectively. In the present embodiment, it can be seen that the concentration of potassium distributed on the side of the first type doped semiconductor layer 120 close to the first electrode 110 is substantially higher than the concentration of the side close to the second type doped semiconductor layer 130.

3A to 3D are graphs showing the different parameters of photoelectric conversion of the compound solar cell of the embodiment of FIG. 1F versus the concentration of potassium fluoride in the slurry to present a slurry 190 having different concentrations of potassium fluoride. The performance of photoelectric conversion of the compound solar cell 100 when the precursor layer is on PrL. In detail, FIG. 3A plots the open circuit voltage of the compound solar cell 100 versus the concentration of potassium fluoride in the slurry 190. The vertical axis of Fig. 3A represents the open circuit voltage in millivolts, and the horizontal axis represents the concentration of potassium fluoride in the slurry, the unit of which is a percentage. 3B is a graph plotting the short circuit current of the compound solar cell 100 versus the concentration of potassium fluoride in the slurry. The vertical axis of Fig. 3B represents short-circuit current (J _sc ) in milliamps/cm 2 , and the horizontal axis represents the concentration of potassium fluoride in the slurry in units of percentage. 3C is a graph showing the fill factor of the compound solar cell 100 versus the concentration of potassium fluoride in the slurry. The vertical axis of Fig. 3C represents the fill factor in units of percentage, and the horizontal axis represents the concentration of potassium fluoride in the slurry in units of percentage. Figure 3D is a graph plotting the energy conversion efficiency of compound solar cell 100 versus the concentration of potassium fluoride in the slurry. The vertical axis of Fig. 3D represents the energy conversion efficiency in units of percentage, and the horizontal axis represents the concentration of potassium fluoride in the slurry in units of percentage. In Figures 3A through 3D, experimental conditions at concentrations of potassium fluoride in the slurry of 0%, 0.25%, 0.5%, 0.75%, and 1% correspond to experimental data points labeled with different shapes, respectively. For example, in Figure 3A, the experimental data points, also indicated by circles, represent the data points obtained for different experiments at a concentration of potassium fluoride in the slurry of 0.25%. As can be seen from FIGS. 3A to 3D, when the material of the slurry 190 includes an alkali metal compound such as potassium fluoride, the open circuit voltage and the filling factor of the compound solar cell 100 are increased, and the compound solar cell 100 has higher energy. Conversion efficiency.

4A is a graph showing the element content analysis of the light absorbing layer of a compound solar cell with or without potassium fluoride at different depths, please refer to FIG. 4A. The indications of the vertical axis and the horizontal axis of FIG. 4A are the same as those of the vertical axis and the horizontal axis of FIG. 2, respectively, and are not described herein again. "Cu" and "Cd" indicated in Fig. 4 indicate copper and cadmium, respectively. The curve indicating "with potassium fluoride" indicates the compound solar cell 100 of the embodiment of Fig. 1F, and the curve labeled "no potassium fluoride" indicates a compound solar cell of a comparative example. The slurry of the compound solar cell of this comparative example was not coated on the precursor layer with a slurry including potassium fluoride. In detail, the position of the broken line in FIG. 4A indicates the position of the vicinity of the P/N junction of the compound solar cell. As can be seen from FIG. 4A, in the region A, since the compound solar cell 100 of the embodiment of FIG. 1F has the first type doped semiconductor layer 120 having an appropriate potassium concentration distribution, more cadmium near the P/N junction The vacancy of copper can be occupied, so that in the region A, the cadmium element content of the compound solar cell 100 is higher than that of the compound solar cell of the comparative example.

4B shows the current versus voltage curve (I-V curve) of a compound solar cell with or without potassium fluoride, please refer to FIG. 4B. The vertical axis of Fig. 4B represents the current density in milliamps per square centimeter, and the horizontal axis represents the voltage in millivolts. The curve indicating "with potassium fluoride" indicates the compound solar cell 100 of the embodiment of Fig. 1F, and the curve labeled "no potassium fluoride" indicates a compound solar cell of a comparative example. The slurry of the compound solar cell of this comparative example was not coated on the precursor layer with a slurry including potassium fluoride. Specifically, the voltages corresponding to the points P1 and P2 are the open circuit voltages of the compound solar cell 100 and the compound solar cell of the comparative example, respectively. 4B, the open circuit voltage of the compound solar cell 100 is larger than the open circuit voltage of the compound solar cell of the comparative example.

5A to 5D illustrate the performance of different parameters of photoelectric conversion of a compound solar cell of a comparative example. In the process of the compound solar cell of this comparative example, the slurry containing potassium fluoride is coated on the light absorbing layer which has been formed by the heat treatment, and is further subjected to an annealing process to cause potassium to enter the light absorbing layer. In detail, FIG. 5A is a graph showing the open circuit voltage of the compound solar cell of this comparative example versus the concentration of potassium fluoride in the slurry. The vertical axis of Fig. 5A represents the open circuit voltage in millivolts, and the horizontal axis represents the concentration of potassium fluoride in the slurry, the unit of which is a percentage. Figure 5B is a graph showing the short circuit current of the compound solar cell of this comparative example versus the concentration of potassium fluoride in the slurry. The vertical axis of Fig. 5B represents the short-circuit current in milliamperes per square centimeter, and the horizontal axis represents the concentration of potassium fluoride in the slurry in units of percentage. Figure 5C is a graph showing the fill factor of the compound solar cell of this comparative example versus the concentration of potassium fluoride in the slurry. The vertical axis of Fig. 5C represents the fill factor in units of percentage, and the horizontal axis represents the concentration of potassium fluoride in the slurry in units of percentage. Figure 5D is a graph plotting the energy conversion efficiency of a compound solar cell of this comparative example versus the concentration of potassium fluoride in the slurry. The vertical axis of Fig. 5D represents the energy conversion efficiency in units of percentage, and the horizontal axis represents the concentration of potassium fluoride in the slurry in units of percentage. Comparing FIGS. 3A to 3D with FIGS. 5A to 5D, it is understood that the compound solar cell 100 has better component performance, and the compound solar cell 100 has higher energy conversion efficiency.

6A to 6D illustrate the performance of different parameters of photoelectric conversion of a compound solar cell of another comparative embodiment. In the process of the compound solar cell of this comparative example, potassium fluoride was introduced into the light absorbing layer which had been formed by heat treatment in a vacuum evaporation plus annealing manner. In detail, FIG. 6A is a graph showing the open circuit voltage of the compound solar cell of this comparative example versus different annealing temperatures. The vertical axis of Fig. 6A represents the open circuit voltage in millivolts, and the horizontal axis represents different annealing temperatures. Figure 6B is a graph showing the short circuit current of the compound solar cell of this comparative example versus different annealing temperatures. The vertical axis of Fig. 6B represents the short-circuit current in units of milliamperes per square centimeter, and the horizontal axis represents different annealing temperatures. Figure 6C is a graph showing the fill factor of the compound solar cell of this comparative example versus different annealing temperatures. The vertical axis of Fig. 6C represents the fill factor, the unit of which is a percentage, and the horizontal axis represents the different annealing temperatures. Figure 6D is a graph plotting the energy conversion efficiencies of the compound solar cells of this comparative example versus different annealing temperatures. The vertical axis of Fig. 6D represents the energy conversion efficiency, the unit of which is a percentage, and the horizontal axis represents a different annealing temperature. In addition, in FIGS. 6A to 6D, the reference "reference" indicates a control condition in which potassium fluoride is not evaporated. The label "375 ° C KF" indicates that the substrate temperature of potassium fluoride deposited on the surface of the copper indium gallium selenide is 375 degrees Celsius. The label "375 °C KF (KCN)" indicates that the surface of the copper indium gallium selenide is first etched with potassium cyanide (Potassium cyanide), and then the surface of the etched surface is vapor-deposited with potassium fluoride, and when potassium fluoride is evaporated. The substrate temperature is 375 degrees Celsius. The label "425 ° C KF" indicates that the substrate temperature of potassium fluoride deposited on the surface of the copper indium gallium selenide is 425 degrees Celsius. In addition, the label "425 ° C KF (KCN)" indicates that the surface of the copper indium gallium selenide is first etched with potassium cyanide, and then the surface of the etched surface is vapor-deposited with potassium fluoride, and the substrate temperature at the time of vapor deposition of potassium fluoride It is 425 degrees Celsius. Specifically, comparing FIGS. 3A to 3D with FIGS. 6A to 6D, it is understood that the compound solar cell 100 has better component performance, and the compound solar cell 100 has higher energy conversion efficiency.

FIG. 7 illustrates a method of fabricating a light absorbing layer according to an embodiment of the present disclosure. Please refer to FIG. 7. In the present embodiment, the method of fabricating the light absorbing layer can be applied at least to the light absorbing layer AL (first type doped semiconductor layer 120) of the compound solar cell 100 of the embodiment of FIG. 1F. The method for fabricating the light absorbing layer is as follows. In step S710, a precursor layer is formed on the substrate, the precursor layer includes a plurality of nano particles, and the materials of the nano particles include copper oxide, indium oxide, and gallium oxide. In step S720, a slurry is provided on the precursor layer, wherein the material of the slurry includes an alkali metal compound. Further, in step S730, the slurry and the precursor layer are subjected to heat treatment. Specifically, the method for fabricating the light absorbing layer of the embodiment of the present disclosure can at least be sufficiently taught, suggested, and implemented by the description of the embodiment of FIG. 1A to FIG. 1F, and thus will not be described again.

In summary, in the method for fabricating the light absorbing layer of the embodiment, the precursor layer includes a plurality of nano particles, and the materials of the nano particles include copper oxide, indium oxide, and gallium oxide. In addition, the method of fabricating the light absorbing layer includes providing a slurry on the precursor layer, and the material of the slurry includes an alkali metal compound. The compound solar cell of the embodiment of the present invention uses the light absorbing layer fabricated by the above manufacturing method as the first type doped semiconductor layer, and thus the first type doped semiconductor layer includes at least one of a plurality of elements, and these elements It includes alkali metal elements such as potassium, strontium and barium. Further, at least one of these alkali metal elements has an appropriate concentration distribution among the first type doped semiconductor layers. Since the alkali metal element can be distributed in the surface, crystal structure and grain boundary of the light absorbing layer during heat treatment such as selenization, vulcanization or any combination of selenization and vulcanization, the material interface and crystal of the light absorbing layer are made. The passivation effect of the boundary is generated, and the composite probability of the electron hole can be reduced. In addition, the P/N junction can achieve a better energy level matching. Therefore, the compound solar cell can have a higher open circuit voltage and a fill factor in a non-vacuum process, and thus has better energy conversion efficiency.

The present disclosure has been disclosed in the above embodiments, but it is not intended to limit the disclosure, and any person skilled in the art can make some changes and refinements without departing from the spirit and scope of the disclosure. The scope of protection of this disclosure is subject to the definition of the scope of the appended claims.

100‧‧‧ compound solar cells

110‧‧‧First electrode

120‧‧‧First type doped semiconductor layer

122‧‧‧ elements

130‧‧‧Second type doped semiconductor layer

140‧‧‧second electrode

142‧‧‧ Essential zinc oxide layer

144‧‧‧Transparent conductive layer

150‧‧‧electrode

190‧‧‧Slurry

192‧‧‧Alkali metal compounds

194‧‧‧ solvent

A‧‧‧ area

AL‧‧‧Light absorbing layer

P1, P2‧‧ points

PrL‧‧‧ precursor layer

S1‧‧‧ first side

S2‧‧‧ second side

Steps for making S710, S720, S730‧‧‧ light absorbing layer

SUB‧‧‧ substrate

T‧‧‧ thickness

1A-1F are flow diagrams showing the fabrication of a compound solar cell according to an embodiment of the present disclosure. 2 is a graph showing element content analysis of light absorbing layers of the compound solar cell of the embodiment of FIG. 1F at different depths. 3A to 3D are graphs showing the different parameters of photoelectric conversion of the compound solar cell of the embodiment of FIG. 1F versus the concentration of potassium fluoride in the slurry. 4A is a graph showing element content analysis of light absorption layers of compound solar cells with or without potassium fluoride at different depths. Figure 4B shows the current versus voltage curve (I-V curve) for a compound solar cell with or without potassium fluoride. 5A to 5D illustrate the performance of different parameters of photoelectric conversion of a compound solar cell of a comparative example. 6A to 6D illustrate the performance of different parameters of photoelectric conversion of a compound solar cell of another comparative embodiment. FIG. 7 illustrates a method of fabricating a light absorbing layer according to an embodiment of the present disclosure.

Claims (16)

A compound solar cell comprising: a first electrode; a second electrode; a first type doped semiconductor layer disposed between the first electrode and the second electrode, and a second type doped semiconductor layer, Disposed between the first type doped semiconductor layer and the second electrode, wherein the first type doped semiconductor layer has a first side close to the first electrode and a first type close to the second type doped semiconductor layer a second side, the first type doped semiconductor layer includes at least one of a plurality of elements, and the elements include potassium, germanium, and germanium, wherein at least one of the elements has a high concentration on the first side The concentration on the second side. The compound solar cell according to claim 1, wherein the first type doped semiconductor layer comprises a group IB element, a group IIIA element, a group VIA element or a combination thereof, or a group IB element, a group IIB element, or a group IVA. Element, group VIA element, or a combination thereof. The compound solar cell of claim 1, wherein the first electrode comprises molybdenum, silver, aluminum, chromium, titanium, nickel, gold or a combination thereof. The compound solar cell of claim 1, wherein one of the first type doped semiconductor layer and the second type doped semiconductor layer is a P type doped semiconductor layer, and the first type is doped The other of the hetero semiconductor layer and the second type doped semiconductor layer is an N-type doped semiconductor layer. The compound solar cell of claim 1, further comprising a substrate, wherein the first electrode is disposed between the first type doped semiconductor layer and the substrate. A method for fabricating a light absorbing layer: forming a precursor layer on a substrate, the precursor layer comprising a plurality of nano particles, and the materials of the nano particles comprise copper oxide, indium oxide and gallium oxide; A slurry is provided on the precursor layer, wherein the material of the slurry comprises an alkali metal compound; and the slurry and the precursor layer are subjected to a heat treatment. The method of fabricating a light absorbing layer according to claim 6, wherein the method of forming the precursor layer on the substrate comprises: coating a precursor on the substrate to form the precursor layer. The method for fabricating a light absorbing layer according to claim 6, wherein the method for providing the slurry on the precursor layer comprises: by capillary coating, spin coating, brush coating, blade coating, spraying Coating or printing is applied to coat the slurry onto the precursor layer. The method for producing a light absorbing layer according to claim 6, wherein the slurry further comprises a solvent, and the alkali metal compound is uniformly dispersed in the solvent. The method for producing a light absorbing layer according to claim 9, wherein the solvent comprises water, an alcohol solvent, an ester solvent, a ketone solvent, an ether solvent, an amine solvent, an acid solvent, a base solvent or Its combination. The method for producing a light absorbing layer according to claim 6, wherein the alkali metal compound has a concentration by weight in the slurry of 0.01% to 0.6%. The method for fabricating a light absorbing layer according to claim 9, further comprising: after the slurry is provided on the precursor layer, the slurry is subjected to a drying treatment to volatilize the solvent. The method for producing a light absorbing layer according to claim 6, wherein the alkali metal compound comprises at least one of a plurality of elements, and the elements include potassium, rubidium, and cesium. The method for fabricating a light absorbing layer according to claim 6, wherein the slurry provided on the precursor layer forms a film layer, and the film layer has a thickness of from 3 nm to 100 nm. In the range. The method for fabricating a light absorbing layer according to claim 13, wherein the method of performing the heat treatment on the slurry and the precursor layer comprises: placing the slurry and the precursor layer in a gas atmosphere A light absorbing layer is formed, wherein the gas environment comprises a gas of a Group VIA element, and the temperature of the gas environment falls within a range of 300 degrees Celsius to 600 degrees Celsius. The method for fabricating a light absorbing layer according to claim 15, wherein the light absorbing layer comprises at least one of the elements, and at least one of the elements is at a concentration higher than the substrate The concentration of the substrate.