JP2009158603A - Photoelectric conversion device, electronic equipment, manufacturing method of photoelectric conversion device, and manufacturing method of electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion device which has excellent characteristics, especially, a superior photoelectric conversion device using a liquid silicon material. <P>SOLUTION: The manufacturing method of the photoelectric conversion device includes a first stage of forming a microcrystalline silicon layer (15) of a first conductivity type, a second stage of coating the microcrystalline silicon layer with the liquid silicon material, and a third stage of making the liquid crystal silicon material amorphous, wherein an amorphous sillicon layer (17) is formed among microcrystal grains (15g) in the microcrystalline silicon layer and on the microcrystalline silicon layer (15) by the second and third stages. In this method, the liquid silicon material enters among microcrystal grains and becomes amorphous. Then, the microcrystalline grains and amorphous silicon layer come into contact with each other to improve the interface area. The photoelectric conversion efficiency can thus be improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion device, in particular, a photoelectric conversion device using a liquid silicon material, a manufacturing method thereof, and the like.

The development of solar cells (photoelectric conversion devices) is drawing attention as an energy-saving, resource-saving and clean energy source. A solar cell is a power device that uses the photovoltaic effect to directly convert light energy into electric power. Although there are various configurations, for example, a solar cell of HIT (Heterojunction with Intrinsic Thin-layer) type is given as a solar cell having high conversion efficiency and good temperature characteristics. This HIT type solar cell is formed by laminating an amorphous silicon layer and a translucent conductive film on one or both sides of a crystalline silicon substrate (see, for example, Patent Document 1 below).
JP 2003-282905 A

  The present inventors are conducting research and development on solar cells (photoelectric conversion devices and semiconductor devices) using a liquid silicon material, and studying solar cells that are easy to manufacture and have good characteristics.

  In particular, in order to improve the conversion efficiency, it is necessary to increase the interface area between the light absorption layer and the photoelectric conversion layer. For example, in Patent Document 1 described above, a concavo-convex structure on the order of several microns is formed on the crystalline silicon surface.

  However, in the structure of Patent Document 1, the photolithography process and the etching process are complicated, and the manufacturing cost may increase. Further, in such a structure, the interfacial area contributing to photoelectric conversion can be increased, but the increase is limited.

  Therefore, it is desired to develop a new structure of a solar cell that can easily improve the interfacial area. In addition, development of cost reduction and simplification of the manufacturing method of the solar cell is desired.

  Therefore, a specific embodiment according to the present invention aims to provide a photoelectric conversion device having good characteristics and a method for manufacturing the photoelectric conversion device. In particular, an object of the present invention is to provide a good photoelectric conversion device using a liquid silicon material and a manufacturing method thereof.

  The photoelectric conversion device according to the present invention includes a first conductivity type microcrystalline silicon layer and an amorphous silicon layer formed on the microcrystalline silicon layer. With this configuration, the interface area between the microcrystalline silicon layer and the amorphous silicon layer can be improved. Therefore, the photoelectric conversion efficiency can be improved. The amorphous silicon layer is intrinsic.

  For example, the amorphous silicon layer is a deposited film. Thus, a deposited film may be used as the amorphous silicon layer.

  The photoelectric conversion device according to the present invention includes a first conductivity type microcrystalline silicon layer, and an amorphous silicon layer formed between the microcrystalline grains in the microcrystalline silicon layer and on the microcrystalline silicon layer. According to such a configuration, the fine crystal grains and the amorphous silicon layer come into contact with each other, and the interface area can be improved. Therefore, the photoelectric conversion efficiency can be improved.

  For example, the amorphous silicon layer is formed by solidifying a liquid silicon material applied on the microcrystalline silicon layer. According to such a configuration, the amorphous silicon layer can be easily disposed between the microcrystalline grains.

  For example, a second conductive type amorphous silicon layer formed on the amorphous silicon layer and an electrode formed on the second conductive type amorphous silicon layer. In this way, the second conductivity type amorphous silicon layer and the electrode may be disposed.

  The electronic device according to the present invention includes the solar cell. According to such a configuration, the characteristics of the electronic device can be improved. In addition, the productivity of such electronic devices can be improved.

  The manufacturing method of the photoelectric conversion device according to the present invention includes a first step of forming a first conductivity type microcrystalline silicon layer and a second step of forming an amorphous silicon layer on the microcrystalline silicon layer by using a deposition method. And having. According to this method, the amorphous silicon layer is deposited on the microcrystalline grains of the microcrystalline silicon layer, and the interfacial area of these layers can be improved by the unevenness. Therefore, a photoelectric conversion device with improved photoelectric conversion efficiency can be manufactured.

  For example, the second step includes a step of depositing amorphous silicon by a sputtering method or a step of amorphizing after depositing a silicon film by a CVD method. As described above, a sputtering method or a CVD method can be used as the deposition method.

  The method for manufacturing a photoelectric conversion device according to the present invention includes a first step of forming a first conductivity type microcrystalline silicon layer, a second step of applying a liquid silicon material on the microcrystalline silicon layer, and the liquid silicon. A third step of making the material amorphous. According to this method, the liquid silicon material penetrates between the microcrystalline grains and becomes amorphous. Therefore, the microcrystalline grains and the amorphous silicon layer come into contact with each other, and the interface area can be improved. Therefore, a photoelectric conversion device with improved photoelectric conversion efficiency can be manufactured.

  For example, an amorphous silicon layer is formed between the microcrystalline grains in the microcrystalline silicon layer and on the microcrystalline silicon layer by the second and third steps. Thus, since the liquid silicon material penetrates between the microcrystalline grains and becomes amorphous, an amorphous silicon layer is formed between the microcrystalline grains in the microcrystalline silicon layer. An amorphous silicon layer can remain on the layer.

  For example, the method includes a step of forming a second conductivity type amorphous silicon layer on the amorphous silicon layer and a step of forming an electrode on the second conductivity type amorphous silicon layer. In this manner, the second conductivity type amorphous silicon layer and the electrode may be formed.

  The manufacturing method of the electronic device which concerns on this invention has the manufacturing method of the said solar cell. According to such a method, an electronic device having good characteristics can be manufactured. In addition, the productivity of such electronic devices can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same or related code | symbol is attached | subjected to what has the same function, and the repeated description is abbreviate | omitted.
<Structure of solar cell>
1-4 is process sectional drawing which shows the manufacturing method of the solar cell (photoelectric conversion apparatus) of this Embodiment. As shown in the final process cross-sectional view of FIG. 4B, the solar cell (porous HIT type silicon thin film solar cell) of the present embodiment includes a substrate 11, a lower electrode 13, a first conductivity type microcrystalline silicon. A film (layer) 15, an intrinsic amorphous silicon film (layer) 17, a second conductivity type silicon film 19, and an upper electrode 21 are included.

  The first and second conductivity types are n-type or p-type. In the case of n-type, n-type impurities such as phosphorus are included, and in the case of p-type, p-type impurities such as boron are included. Intrinsic (i-type) is a semiconductor film that is not doped with impurities and has a lower impurity concentration than an n-type or p-type semiconductor film (layer). The crystal grain size (diameter) of the microcrystal is 0.01 μm or more and 10 μm or less, more preferably 0.01 μm or more and 1 μm or less. Further, when amorphous silicon is heat-treated at a low temperature of 400 to 600 ° C. (for example, about 500 ° C.), a fine crystal layer is generated. This can also be said to be microcrystalline silicon.

  For example, as shown in FIG. 5, when the lower electrode 13 and the upper electrode 21 are connected by an external circuit (wiring or the like) 8, a current (photoexcitation current) flows through the external circuit 8.

Here, the characteristic configuration of the present embodiment is that an amorphous silicon film 17 is formed between and on the microcrystalline grains 15g constituting the microcrystalline silicon film 15 (see FIG. 3). ). FIG. 3 shows a partially enlarged view of the interface between the microcrystalline silicon film 15 and the amorphous silicon film 17.
<Solar cell manufacturing process>
Next, a method for manufacturing the solar cell (photoelectric conversion device) of the present embodiment will be described with reference to FIGS.

  As shown in FIG. 1A, for example, a quartz glass substrate is prepared as the substrate 11. As the substrate 1, other glass substrates such as soda glass substrates, resin substrates using ceramics such as polycarbonate and polyethylene terephthalate, ceramic substrates, and the like may be used. If the substrate 11 is light transmissive, light can be collected from the back side (lower side in the figure) of the substrate 11. However, since it is possible to use only light from above the substrate 11, a material having low light transmittance may be used as the material of the substrate 11 or the lower electrode 13 described later. Further, a base film may be formed in the lower layer of the substrate 11 as necessary, or the substrate 11 itself may be composed of a plurality of layers of materials.

  Next, an Al (aluminum) film is formed on the substrate 11 as the lower electrode (first electrode) 13. For example, the lower electrode 13 is formed by depositing Al on the substrate 11 by sputtering and patterning as necessary. For example, a photoresist film is formed on the Al film, and is exposed and developed (photolithography) to form a substantially rectangular (see FIG. 5) photoresist film. Next, the Al film is etched using the photoresist film as a mask. Next, the remaining photoresist film is removed. A series of steps from formation to removal of the photoresist film is called patterning.

As a material of the lower electrode 13, in addition to Al, nickel (Ni), cobalt (Co), platinum (Pt), silver (Ag), gold (Au), copper (Cu), molybdenum (Mo), titanium (Ti) ), Metal materials such as tantalum (Ta) may be used. Moreover, you may use these alloys. Alternatively, a conductive metal oxide such as indium tin oxide (ITO), fluorine-doped tin oxide (FTO), indium oxide (IO), or tin oxide (SnO ₂ ) may be used. These are transparent conductive oxides, and their use can improve the light transmission from the back side (the lower side in the figure) of the substrate 11. Further, a conductive carbon material such as carbon, carbon nanotube, or fullerene may be used. Moreover, you may use in combination of 2 or more types of said various materials. These material films can be formed by a sputtering method, a spray method, an ink jet method, or the like.

Next, as shown in FIG. 1B, a microcrystalline silicon film 15 doped with a p-type impurity is formed as a first conductive semiconductor film on the substrate 11 including the lower electrode 13. The microcrystalline silicon film 15 is formed by RF (Radio Frequency) magnetron sputtering using, for example, a silicon (Si) target doped with a p-type impurity (for example, boron) at a high concentration. For example, in order to prevent oxidation of the deposited film, 7N (99.99999% or more) pure hydrogen is allowed to flow into the chamber (processing chamber), and the pressure in the chamber is 0.3 to 1.0 Torr (1 Torr = 1). 33322 × 10 ² Pa), an RF power of 100 W to 450 W, a substrate temperature of 60 to 100 ° C., and a deposition rate of 3 to 25 nm / min. The film thickness of the microcrystalline silicon film 15 is, for example, several μm to several hundred μm, and preferably 5 μm or more.

  According to the study by the present inventors, a microcrystalline silicon film 15 having a thickness of about 12 μm was obtained by forming a film at a deposition rate of 25 nm / min for 8 hours. In this case, the crystal grain size (average) of the microcrystals in the film was about 20 nm. Note that FIG. 1B is a diagram schematically showing microcrystalline grains 15g in the microcrystalline silicon film 15 for easy understanding, and the number and the stacked state thereof are different from those of an actual deposited film. Note that as a method for forming the microcrystalline silicon film 15, a CVD (Chemical Vapor Deposition) method, a solution process, or the like may be used in addition to the above sputtering method. Alternatively, an amorphous silicon film may be deposited and microcrystallized by heat treatment or the like.

Next, as shown in FIG. 2A, a liquid silicon material 17 a is applied over the microcrystalline silicon film 15. As the liquid silicon material, for example, a liquid in which polysilane (polymer hydrogenated silane, Si _n H _{2n + 2} (n> 2)) is dispersed in an organic solvent can be used. This liquid silicon material 17 is applied onto the microcrystalline silicon film 15 by spin coating. Next, the liquid silicon material 17 is subjected to heat treatment at 250 ° C. to 350 ° C. for about 10 minutes to 1 hour to be amorphous (solidified and fired). Thereby, an amorphous silicon film (photoelectric conversion layer) 17 is formed (FIG. 2B).

  Here, since the liquid silicon material 17a penetrates between the microcrystalline grains 15g and becomes amorphous, an amorphous silicon film 17 is formed between the microcrystalline grains 15g and on the microcrystalline silicon film 15 (see FIG. 3). . 3 is a partial enlarged view of the interface between the microcrystalline silicon film 15 and the amorphous silicon film 17, for example, as shown in FIG. The thickness of the amorphous silicon film 17 on the microcrystalline silicon film 15 is preferably about 5 to 50 nm.

  Further, as the liquid silicon material 17a, an organic silicon compound may be used in addition to the above. Further, the liquid silicon material 17a may be applied using an inkjet method in addition to the spin coating method. In this case, the liquid silicon material 17a can be applied (discharged) only to a desired region.

Next, as shown in FIG. 4A, a silicon film 19 doped with n-type impurities is formed on the amorphous silicon film 17 as a second conductivity type semiconductor film. The silicon film 19 is formed using, for example, an impurity-added liquid silicon material obtained by adding a phosphorus compound such as yellow phosphorus (P ₄ ) to the liquid silicon material. An impurity-added liquid silicon material is applied onto the amorphous silicon film 17 by a spin coating method. Next, the impurity-added liquid silicon material is heat-treated and solidified (fired). The heat treatment conditions are, for example, about 250 ° C. to 350 ° C. and about 10 minutes to 1 hour, and the film is made amorphous.

  Next, as shown in FIG. 4B, an ITO film is formed on the silicon film 19 as the upper electrode (second electrode) 21. For example, an ITO film is deposited on the silicon film 19 by a sputtering method, and the upper electrode 21 is formed by patterning as necessary. At this time, the underlying silicon film 19, amorphous silicon film 17, and microcrystalline silicon film 15 may be patterned simultaneously. Further, at this time, by patterning into a shape smaller than the lower electrode 13, the lower electrode 13 is exposed and contact with the external circuit (wiring, etc.) 8 becomes possible (see FIG. 5).

  In the present embodiment, the upper electrode 21, the lower electrode 13, and the like are patterned in a substantially rectangular shape. However, the present invention is not limited to these shapes, and may have other shapes.

  Next, an interlayer insulating layer (not shown), wiring connected to the lower electrode 13 or the upper electrode 21 and the like are appropriately formed, and the external circuit (8) and the solar cell of the present embodiment are connected.

  FIG. 5 is a perspective view showing the configuration of the solar cell of the present embodiment. As shown in FIG. 5, for example, light such as sunlight is incident to convert light energy into electrical energy.

  In particular, according to the HIT type solar cell, by forming an intrinsic amorphous silicon film between the first and second conductivity type silicon films (15, 19), these interface characteristics are improved, and power generation loss is reduced. Can be reduced.

  Furthermore, according to the present embodiment, the first conductive type silicon film is the microcrystalline silicon film 15, the liquid silicon material is used as the intrinsic amorphous silicon film 17, and the amorphous silicon film 17 is also formed between the microcrystalline grains 15g. Since it is formed, the interface area (interface area, contact area, boundary area) between the amorphous silicon film 17 and the microcrystalline grains (microcrystalline silicon film) increases, and the power generation efficiency (photoelectric conversion efficiency) can be improved. .

Next, simulation results by the present inventors will be described. An acquisition characteristic (voltage-current characteristic) of a solar cell using a microcrystalline silicon film having a film thickness of 12 μm formed by the above manufacturing process was measured using a solar simulator. FIG. 6 shows the acquisition characteristics. The vertical axis represents photocurrent density (mA / cm ² ), and the horizontal axis represents output voltage (V). Simulation was performed with AM1.5G and 100 mW / cm ² , which are irradiation conditions of simulated sunlight.

  Graph (A) is the characteristic of the solar cell of the present embodiment, and graph (B) is a comparative example. In the solar cell of the comparative example, a single crystal silicon film having a film thickness of 625 μm is used instead of the microcrystalline silicon film 15, and an amorphous silicon layer 17 is formed by a CVD method.

  Even though the thickness of the microcrystalline silicon film 15 is 12 μm, which is 1/50 or less of 625 μm, the short-circuit current value IscA remains only about 10% lower than IscB.

  In this way, characteristics comparable to the comparative example were confirmed. It was also found that high photoelectric conversion efficiency was obtained even when the microcrystalline silicon film 15 was thinned.

  As described above in detail, according to the present embodiment, the first conductive type silicon film is the microcrystalline silicon film 15, and a liquid silicon material is used as the intrinsic amorphous silicon film 17. Since amorphous silicon is also formed, the interfacial area between the amorphous silicon film and the microcrystalline grains (microcrystalline silicon film) increases, and the power generation efficiency can be improved.

  Furthermore, in the comparative example, since the single crystal film is used, the cost is high. However, the solar cell of the present embodiment can provide an inexpensive and highly efficient device.

  Moreover, according to the said manufacturing process, a low-temperature process is possible and it is also possible to make the board | substrate 1 flexible, such as a resin substrate. Therefore, the cost can be reduced and the electronic device can be used for various electronic devices. For example, it can be used as a driving battery for a display device formed on a flexible substrate such as electronic paper.

  Although the microcrystalline silicon film 15 is p-type and the silicon film 17 is n-type in the above embodiment, the microcrystalline silicon film 15 may be n-type and the silicon film 17 may be p-type. In this case, a microcrystalline silicon film 15 is formed using a silicon target doped with an n-type impurity at a high concentration, and a silicon film 17 is formed using an impurity-added liquid silicon material added with a p-type impurity.

  FIG. 7 is a cross-sectional view showing another configuration of the solar cell (photoelectric conversion device) of the present embodiment. In FIG. 4B, the amorphous silicon film 17 is formed using a liquid silicon material, but a deposition method may be used. As shown in FIG. 7, the amorphous silicon film 17A may be formed by sputtering. Alternatively, the amorphous silicon film 17A may be formed by depositing a silicon film by a CVD method and then making it amorphous. In this case, no silicon film is formed between the microcrystalline grains, but the interfacial area between the microcrystalline silicon film 15 and the silicon film 17A increases due to the unevenness of the microcrystalline grains. For example, the interface area becomes larger than that of the comparative example, and the conversion efficiency can be improved.

<Electronic equipment>
The solar cell (photoelectric conversion device) can be incorporated into various electronic devices. There is no limitation on applicable electronic devices, but an example thereof will be described. 8 to 11 illustrate examples of electronic devices using the solar cell of this embodiment.

  FIG. 8 is a plan view showing a calculator to which the solar cell (photoelectric conversion device) of the present invention is applied, and FIG. 9 is a perspective view showing a mobile phone (including PHS) to which the solar cell (photoelectric conversion device) of the present invention is applied. FIG.

  A calculator 100 illustrated in FIG. 8 includes a main body unit 101, a display unit 102 provided on the upper surface (front surface) of the main body unit 101, a plurality of operation buttons 103, and a photoelectric conversion element installation unit 104.

  In the configuration shown in FIG. 8, five photoelectric conversion elements 1 are arranged in series in the photoelectric conversion element installation unit 104.

  A cellular phone 200 illustrated in FIG. 9 includes a main body portion 201, a display portion 202 provided on the front surface of the main body portion 201, a plurality of operation buttons 203, an earpiece 204, a mouthpiece 205, and a photoelectric conversion element installation portion 206. I have.

  In the configuration illustrated in FIG. 9, the photoelectric conversion element installation unit 206 is provided so as to surround the display unit 202, and a plurality of photoelectric conversion elements 1 are arranged in series.

  In addition to the calculator shown in FIG. 8 and the mobile phone shown in FIG. 9, the electronic apparatus of the present invention can be applied to, for example, an optical sensor, an optical switch, an electronic notebook, an electronic dictionary, a wristwatch, a clock, and the like.

  FIG. 10 is a perspective view illustrating a wrist watch that is an example of an electronic apparatus. The wristwatch 1100 includes a display portion 1101. For example, the solar cell of this embodiment can be incorporated in the outer periphery of the display portion 1101.

  FIG. 11 is a perspective view illustrating an electronic paper which is an example of the electronic apparatus. The electronic paper 1200 includes a main body portion 1201 formed of a flexible substrate and a display portion 1202. The solar cell of this embodiment can be incorporated in the outer periphery of the display portion 1201.

  It should be noted that the examples and application examples described through the above embodiment can be used in appropriate combination according to the application, or can be used with modifications or improvements, and the present invention is limited to the description of the above embodiment. Is not to be done.

It is process sectional drawing which shows the manufacturing method of the solar cell (photoelectric conversion apparatus) of this Embodiment. It is process sectional drawing which shows the manufacturing method of the solar cell (photoelectric conversion apparatus) of this Embodiment. It is process sectional drawing which shows the manufacturing method of the solar cell (photoelectric conversion apparatus) of this Embodiment. It is process sectional drawing which shows the manufacturing method of the solar cell (photoelectric conversion apparatus) of this Embodiment. It is a perspective view which shows the structure of the solar cell of this Embodiment. It is a figure which shows the acquisition characteristic (voltage-current characteristic) of the solar cell (photoelectric conversion apparatus) of this Embodiment. It is sectional drawing which shows the other structure of the solar cell (photoelectric conversion apparatus) of this Embodiment. It is a top view which shows the calculator to which the solar cell (photoelectric conversion apparatus) of this invention is applied. It is a perspective view which shows the mobile telephone to which the solar cell (photoelectric conversion apparatus) of this invention is applied. It is a perspective view which shows the wristwatch which is an example of an electronic device. It is a perspective view which shows the electronic paper which is an example of an electronic device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 8 ... External circuit, 11 ... Substrate, 13 ... Lower electrode, 15 ... Microcrystalline silicon film, 15g ... Fine crystal grain, 17, 17A ... Amorphous silicon film, 17a ... Liquid silicon material, 19 ... Silicon film, 21 ... Upper electrode DESCRIPTION OF SYMBOLS 100 ... Calculator 101 ... Main-body part 102 ... Display part 103 ... Operation button 104 ... Photoelectric conversion element installation part 200 ... Cell-phone, 201 ... Main-body part 202 ... Display part 203 ... Operation button 204 ... Earpiece, 205 ... Mouthpiece, 206 ... Photoelectric conversion element installation part, 1100 ... Wristwatch, 1101 ... Display part, 1200 ... Electronic paper, 1201 ... Display part, IscA, IscB ... Short-circuit current value

Claims (12)

A first conductivity type microcrystalline silicon layer;
An amorphous silicon layer formed on the microcrystalline silicon layer;
A photoelectric conversion device comprising:   The photoelectric conversion device according to claim 1, wherein the amorphous silicon layer is a deposited film. A first conductivity type microcrystalline silicon layer;
An amorphous silicon layer formed between and on the microcrystalline silicon layer in the microcrystalline silicon layer;
A photoelectric conversion device comprising:   4. The photoelectric conversion device according to claim 3, wherein the amorphous silicon layer is formed by solidifying a liquid silicon material applied on the microcrystalline silicon layer. A second conductivity type amorphous silicon layer formed on the amorphous silicon layer;
An electrode formed on the second conductivity type amorphous silicon layer;
5. The photoelectric conversion device according to claim 1, comprising:   An electronic apparatus comprising the photoelectric conversion device according to claim 1. A first step of forming a first conductivity type microcrystalline silicon layer;
A second step of forming an amorphous silicon layer on the microcrystalline silicon layer using a deposition method;
A process for producing a photoelectric conversion device, comprising:   8. The method of manufacturing a photoelectric conversion device according to claim 7, wherein the second step includes a step of depositing amorphous silicon by a sputtering method, or a step of depositing a silicon film by CVD and then amorphizing. . A first step of forming a first conductivity type microcrystalline silicon layer;
A second step of applying a liquid silicon material on the microcrystalline silicon layer;
A third step of making the liquid silicon material amorphous;
A process for producing a photoelectric conversion device, comprising:   10. The photoelectric conversion device according to claim 9, wherein an amorphous silicon layer is formed between and on the microcrystalline grains in the microcrystalline silicon layer by the second and third steps. Method. Forming a second conductivity type amorphous silicon layer on the amorphous silicon layer;
Forming an electrode on the second conductivity type amorphous silicon layer;
The method for manufacturing a photoelectric conversion device according to claim 7, comprising:   A method for manufacturing an electronic device, comprising the method for manufacturing a photoelectric conversion device according to claim 7.