JP2006128630A - Photovoltaic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deterioration of output characteristics of a solar battery in a heating process after forming an amorphous semiconductor thin film layer by a plasma CVD method. <P>SOLUTION: A photovoltaic device is formed with a substantially intrinsic amorphous silicon layer containing hydrogen between an n-type single crystal silicon substrate and a p-type amorphous silicon layer containing hydrogen. A trap layer whose hydrogen concentration is lower than that of the intrinsic amorphous silicon layer is formed between the p-type amorphous silicon layer and the intrinsic amorphous silicon layer. By this trap layer, hydrogen diffusion from the intrinsic amorphous layer to the p-type amorphous silicon layer is prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photovoltaic device having a hetero semiconductor junction.

  In recent years, as photovoltaic devices, research and practical application of solar cells using crystalline semiconductors such as single crystal silicon and polycrystalline silicon have been actively conducted. Among them, a solar cell having a hetero semiconductor junction constituted by combining amorphous silicon and crystalline silicon can form the junction by a low temperature process such as a plasma CVD method at 200 ° C. or less, and Because of its high conversion efficiency, it has attracted attention. In such a photovoltaic device, in order to improve the photoelectric conversion efficiency, it is necessary to improve the fill factor (FF) while maintaining a high short circuit current (Isc) and an open circuit voltage (Voc).

  Therefore, a substantially intrinsic amorphous silicon layer containing hydrogen (i-type amorphous silicon layer) is inserted between the n-type single crystal silicon substrate and the p-type amorphous silicon layer containing hydrogen. So-called H. I. T.A. Solar cells having a (Heterojunction with Intrinsic Thin-layer) structure have been developed. H.I.T. In the solar cell device having the structure, the optical band gap of the i-type amorphous silicon layer is in contact with the p-type amorphous silicon layer in order to further reduce the recombination of photogenerated carriers and improve the photoelectric conversion efficiency. A wide configuration has been proposed on the side (see, for example, Patent Document 1).

H. mentioned above. I. T. T. et al. In the solar cell device having the structure, the p-type amorphous silicon layer located on the light incident side is doped with p-type impurities such as hydrogen concentration and boron (B) in consideration of both conductivity and light transmittance. And the like are configured in an optimized layer. In addition, the i-type amorphous silicon layer is also a layer in which the composition such as the hydrogen concentration is optimized in order to improve the interface characteristics. In this way, the conventional HIT.com that simply optimizes the p-type amorphous silicon layer and the i-type amorphous silicon layer, respectively. In the solar cell having the structure, the hydrogen concentration of the i-type amorphous silicon layer is higher than that of the p-type amorphous silicon layer.
JP 2002-76409 A

  By the way, when various solar cells having an amorphous silicon layer formed by plasma CVD are heated at a high temperature of 200 ° C. or higher for a long time, the output characteristics deteriorate. For this reason, the electrode formation and lamination process after the formation of the amorphous silicon layer is managed so as not to exceed the temperature of the CVD process as much as possible.

  The causes of the characteristic deterioration due to high temperature heating are (1) diffusion of electrode material into hydrogen-containing valence-controlled amorphous semiconductor thin film, and (2) substantially intrinsic amorphous material containing hydrogen. The diffusion of the dopant into the semiconductor thin film layer, (3) the diffusion of hydrogen, etc. can be considered. Of these, (3) shows the effect at the lowest temperature.

  In particular, due to hydrogen diffusion from the i-type amorphous silicon layer to the p-type amorphous silicon layer, the activation rate of boron (B), which is a dopant, is lowered, the built-in electric field is lowered, and the output characteristics of the solar cell are reduced. There was a problem of being lowered.

  This invention makes it a subject to suppress the fall of the output characteristic of a solar cell in the heating process after forming the amorphous type semiconductor thin film layer by plasma CVD method in view of the above-mentioned problem.

The present invention relates to a crystalline semiconductor substrate, a substantially intrinsic amorphous semiconductor thin film layer containing hydrogen provided on the crystalline substrate, and hydrogen provided on the intrinsic amorphous semiconductor thin film. An amorphous semiconductor thin film layer controlled by valence electrons, and the amorphous semiconductor thin film layer controlled by valence electrons and the intrinsic amorphous semiconductor thin film layer. And a hydrogen diffusion suppression region that suppresses hydrogen diffusion from the amorphous semiconductor thin film layer to the valence electron controlled amorphous semiconductor thin film layer.

  As described above, according to the present invention, hydrogen diffusion from the intrinsic amorphous semiconductor thin film layer to the valence electron controlled amorphous semiconductor thin film layer can be suppressed by the hydrogen diffusion suppression region. As a result, it is possible to suppress a decrease in output characteristics of the solar cell in the heating process after the formation of the amorphous semiconductor thin film layer.

  The hydrogen diffusion suppression region has a hydrogen concentration in the intrinsic amorphous semiconductor thin film layer in the vicinity of the interface between the valence-controlled amorphous semiconductor thin film layer and the intrinsic amorphous semiconductor thin film layer. It can be formed in a region having a higher hydrogen concentration.

  As described above, by providing a region having a higher hydrogen concentration than the intrinsic amorphous semiconductor thin film layer, a hydrogen diffusion suppression region can be configured. The region having a high hydrogen concentration can suppress hydrogen diffusion from the intrinsic amorphous semiconductor thin film layer to the amorphous semiconductor thin film layer controlled by valence electrons.

  The hydrogen diffusion suppression region is formed in the vicinity of the interface between the valence electron controlled amorphous semiconductor thin film layer and the intrinsic amorphous semiconductor thin film layer. It can be formed in a region where the hydrogen concentration is higher than the hydrogen concentration and is doped with impurities for controlling valence electrons of the same type as the amorphous semiconductor thin film layer controlled for valence electrons.

  As described above, a region having a hydrogen concentration higher than that of the intrinsic amorphous semiconductor thin film layer and doped with impurities for controlling valence electrons of the same type as the amorphous semiconductor thin film layer controlled by valence electrons By providing this, a hydrogen diffusion suppression region can be configured. The region can suppress hydrogen diffusion from the intrinsic amorphous semiconductor thin film layer to the amorphous semiconductor thin film layer controlled by valence electrons.

  The hydrogen diffusion suppression region is formed in the vicinity of the interface between the valence electron controlled amorphous semiconductor thin film layer and the intrinsic amorphous semiconductor thin film layer. It can be formed with a trap layer having a hydrogen concentration lower than the hydrogen concentration.

  As described above, by providing a trap layer having a hydrogen concentration lower than that of the intrinsic amorphous semiconductor thin film layer, a hydrogen diffusion suppression region can be configured. The trap layer can suppress hydrogen diffusion from the intrinsic amorphous semiconductor thin film layer to the amorphous semiconductor thin film layer controlled by valence electrons.

  The trap layer may be formed of a substantially intrinsic amorphous semiconductor thin film layer.

  The trap layer may be doped with impurities for controlling valence electrons of the same type as the amorphous semiconductor thin film layer controlled for valence electrons.

  The present invention also provides an n-type single crystal silicon substrate, a substantially intrinsic amorphous silicon layer containing hydrogen provided on the single crystal silicon substrate, and the intrinsic amorphous silicon layer. A hydrogen-containing p-type amorphous silicon layer, and the p-type amorphous silicon layer is provided between the p-type amorphous silicon layer and the intrinsic amorphous silicon layer. And a hydrogen diffusion suppressing region that suppresses hydrogen diffusion into the amorphous silicon layer.

  As described above, according to the present invention, hydrogen diffusion from the intrinsic amorphous silicon layer to the p-type amorphous silicon layer can be suppressed by the hydrogen diffusion suppression region. As a result, it is possible to suppress a decrease in output characteristics of the solar cell in the heating process after the formation of the amorphous silicon layer.

  The hydrogen diffusion suppression region is a region whose hydrogen concentration is higher than the hydrogen concentration of the intrinsic amorphous silicon layer in the vicinity of the interface between the p-type amorphous silicon layer and the intrinsic amorphous silicon layer. Can be formed.

  As described above, a hydrogen diffusion suppression region can be configured by providing a region having a higher hydrogen concentration than the intrinsic amorphous silicon layer. Then, hydrogen diffusion from the intrinsic amorphous silicon layer to the p-type amorphous silicon layer can be suppressed by the region having a high hydrogen concentration.

  The hydrogen diffusion suppression region has a hydrogen concentration higher than the hydrogen concentration of the intrinsic amorphous silicon layer in the vicinity of the interface between the p-type amorphous silicon layer and the intrinsic amorphous silicon layer. In addition, it can be formed in a region doped with the p-type impurity.

  As described above, by providing a region having a higher hydrogen concentration than the intrinsic amorphous silicon layer and doped with the p-type impurity, a hydrogen diffusion suppression region can be configured. The region can suppress hydrogen diffusion from the intrinsic amorphous silicon layer to the p-type amorphous silicon layer.

  The hydrogen diffusion suppression region is a trap layer having a hydrogen concentration lower than the hydrogen concentration of the intrinsic amorphous silicon layer in the vicinity of the interface between the p-type amorphous silicon semiconductor thin film layer and the intrinsic amorphous silicon layer. May be formed.

  As described above, by providing a trap layer having a hydrogen concentration lower than that of the intrinsic amorphous silicon layer, a hydrogen diffusion suppression region can be configured. The trap layer can suppress hydrogen diffusion from the intrinsic amorphous silicon layer to the p-type amorphous silicon layer.

  The trap layer may be formed of a substantially intrinsic amorphous silicon layer. In this case, the thickness of the trap layer is 1 nm to 5 nm, preferably 1 nm to 2 nm.

  The trap layer may be composed of an amorphous silicon layer doped with p-type impurities. In this case, the thickness of the trap layer is 0.1 nm or more and less than 3 nm, preferably 0.3 nm or more and 2 nm or less.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, a photovoltaic device having an H.I.T. structure to which the present invention is applied will be described with reference to FIG. FIG. 1 shows an H.I.T. It is a schematic sectional drawing which shows the photovoltaic apparatus of a structure.

  As shown in FIG. 1, this photoelectric conversion device has a resistivity of about 1 Ω · cm and a thickness of about 300 μm as a crystalline semiconductor substrate and an n-type single crystal silicon (C−) having a (100) plane. (Si) substrate 1 (hereinafter referred to as n-type single crystal silicon substrate 1). On the surface of the n-type single crystal silicon substrate 1, pyramidal irregularities having a height of several μm to several tens of μm are formed. On this n-type single crystal silicon substrate 1, a substantially intrinsic i-type amorphous film having a thickness of 3 nm to 250 nm is formed as a substantially intrinsic amorphous semiconductor thin film layer containing hydrogen by RF plasma CVD. A quality silicon (a-Si: H) layer 2 is formed. On the i-type amorphous silicon layer 2, a p-type amorphous silicon layer 3 having a thickness of about 5 nm is formed as a hydrogen-containing valence-controlled amorphous semiconductor thin film layer. .

In this embodiment, an ITO (Indium Thin Oxide) film 4 is formed on the p-type amorphous silicon layer 3 as an oxide transparent conductive film having a thickness of about 100 nm by a magnetron sputtering method. The ITO film 4 is made of In ₂ O ₃ (indium oxide) to which SnO ₂ (tin oxide) is added.

  A comb-shaped collecting electrode 5 made of silver paste is formed in a predetermined region on the upper surface of the ITO film 4.

A substantially intrinsic i-type amorphous silicon layer 6 having a thickness of about 5 nm is formed on the lower surface of the n-type single crystal silicon substrate 1. An n-type amorphous silicon layer 7 having a thickness of about 20 nm is formed on the i-type amorphous silicon layer 6. As described above, the i-type amorphous silicon layer 6 and the n-type amorphous silicon layer 7 are sequentially formed on the lower surface of the n-type single crystal silicon substrate 1, thereby forming a so-called BSF (Back Surface Field) structure. Is formed. Furthermore, an ITO film 8 is formed on the n-type amorphous silicon layer 7 as a transparent oxide conductive film having a thickness of about 100 nm in this embodiment by magnetron sputtering. The ITO film 8 is formed of In ₂ O ₃ to which SnO ₂ is added.

  A comb-shaped collecting electrode 9 made of silver paste is formed in a predetermined region on the upper surface of the ITO film 8.

  A manufacturing example of the above-described photovoltaic device will be described below. The cleaned n-type single crystal silicon substrate 1 is introduced into a vacuum chamber and heated to an appropriate temperature (200 ° C. or lower) to remove moisture adhering to the substrate surface as much as possible. Next, hydrogen gas is introduced and the substrate surface is cleaned by plasma discharge.

Thereafter, silane (SiH ₄ ) gas and hydrogen gas are introduced to form a non-doped i-type amorphous silicon layer 2. Subsequently, diborane (B ₂ H ₆ ) gas is introduced as SiH ₄ gas, hydrogen gas, and doping gas to form the p-type amorphous silicon layer 3 to complete the pn junction. Further, an indium tin oxide layer is formed by sputtering as the surface electrode 4, and a silver electrode is formed by screen printing as the collecting electrode 5, and this silver electrode is baked to form the collecting electrode 5.

  Note that a non-doped i-type amorphous silicon layer 6, an n-type amorphous silicon layer 7, and back electrode layers 8 and 9 may be formed on the opposite side of the substrate 1 to form a so-called BSF structure. At this time, the order of creating the p-type layer may be created from the back side (n-type side) or from the front side (p side).

  The substrate is p-type, the front side is a non-doped amorphous silicon layer, the n-type amorphous silicon layer, the indium tin oxide layer, the silver collector electrode, the back side is the non-doped amorphous silicon layer, the p-type When the amorphous silicon layer and the back electrode layer are formed, they can be handled in the same manner. Table 1 shows the conditions for forming each amorphous silicon layer at the time of producing a solar cell as a photovoltaic device.

  As described above, the conventional H.264, which optimized the p-type amorphous silicon layer 3 and the i-type amorphous silicon layer 2 respectively. I. T.A. In the solar cell having the structure, the hydrogen concentration of the i-type amorphous silicon layer 2 is higher than that of the p-type amorphous silicon layer 3.

  FIG. I. T.A. 2 schematically shows a hydrogen concentration profile in the vicinity of an interface between a p-type amorphous silicon layer 3 and an i-type amorphous silicon layer 2 of a solar cell having a structure. The hydrogen concentration of the i-type amorphous silicon layer 2 is higher than that of the p-type amorphous silicon layer 3, and in the vicinity of the interface between the p-type amorphous silicon layer 3 and the i-type amorphous silicon layer 2, A negative hydrogen concentration gradient is formed from the i-type amorphous silicon layer (i layer) 2 toward the p-type amorphous silicon layer (p layer) 3. For this reason, the film is formed by high-temperature heating such as baking for forming a collecting electrode performed after the interface between the p-type amorphous silicon layer 3 and the i-type amorphous silicon layer 2 is formed or a laminating process for modularization. The hydrogen therein is easily diffused from the i-type amorphous silicon layer 2 to the p-type amorphous silicon layer 3.

  FIG. 3 shows the H.264 in the first embodiment of the present invention. I. T.A. 2 schematically shows a hydrogen concentration profile in the vicinity of an interface between a p-type amorphous silicon layer and an i-type amorphous silicon layer of a solar cell having a structure. As shown in FIG. 3, in the first embodiment of the present invention, the hydrogen concentration increases from the i-type amorphous silicon layer 2 toward the p-type amorphous silicon layer 3 contrary to the prior art. Thus, a positive hydrogen concentration gradient is provided. That is, the hydrogen concentration of the p-type amorphous silicon layer 3 is set higher than that of the i-type amorphous silicon layer 2 to form a hydrogen diffusion suppression region. With this configuration, hydrogen diffusion into the p-type amorphous silicon layer 3 is prevented.

In order to make the hydrogen concentration in the p-type amorphous silicon layer 3 higher than that in the i-type amorphous silicon layer 2, the following method may be used.
(1) The substrate temperature at the time of forming the p-type amorphous silicon layer 3 is set lower than that at the time of forming the i-type amorphous silicon layer 2. (2) The hydrogen dilution amount at the time of forming the p-type amorphous silicon layer 3 is set higher than that at the time of forming the i-type amorphous silicon layer 2. (3) The film forming pressure at the time of forming the p-type amorphous silicon layer 3 is made higher than that at the time of forming the i-type amorphous silicon layer 2. (4) The RF input power when forming the p-type amorphous silicon layer 3 is made higher than when forming the i-type amorphous silicon layer 2.

  The first embodiment of the present invention was created by forming the p-type amorphous silicon layer 3 with a higher amount of hydrogen dilution than when forming the i-type amorphous silicon layer 2. Table 2 shows specific conditions for forming the p-type amorphous silicon layer 3 and the i-type amorphous silicon layer 2 on the front side. The conditions on the back side were created according to the conditions shown in Table 1. The i-type amorphous silicon layer 2 was formed with a thickness of 10 nm, and the p-type amorphous silicon layer 3 was formed with a thickness of 5 nm.

  According to Table 2, the first embodiment of the present invention was formed with the hydrogen dilution amount at the time of forming the p-type amorphous silicon layer being higher than that at the time of forming the i-type amorphous silicon layer. FIG. 4 shows the results of measuring the hydrogen concentration profile in the film by SIMS using the first embodiment of the present invention and the conventional apparatus. The conventional apparatus was formed under the same conditions as in the first embodiment except that it was formed with the same hydrogen dilution amount. FIG. 4 shows the H.264 in the first embodiment. I. T.A. It is a figure which shows the hydrogen concentration profile of the interface part of the p-type amorphous silicon layer 3 and the i-type amorphous silicon layer 2 which measured the solar cell of the structure by SIMS.

The SIMS apparatus used for the measurement and the measurement conditions of hydrogen (H) and fluorine (F) are described below. The measurement is performed by counting the number of secondary ions of hydrogen negative ions (H ⁻ ), fluorine negative ions (F ⁻ ), and silicon negative ions (Si ⁻ ) that are emitted by irradiating the sample with cesium positive ions (Cs ⁺ ). The hydrogen concentration is quantified as [H ⁻ ] / [Si ⁻ ] and the fluorine concentration is [F ⁻ ] / [Si ⁻ ]. However, the silicon concentration is 5.0 × 10 ²² / cm ³ . Moreover, the measurement apparatus was ADEPT1010 made from ULVAC-PHI (Physical electronic Information), and ion irradiation energy was 1 keV.

  From the hydrogen concentration profile measured by SIMS shown in FIG. 4, a hydrogen concentration profile similar to the schematic diagram of FIGS. 2 and 3 can be confirmed. In the first embodiment of the present invention, the i-type amorphous silicon layer 2 It can be seen that the p-type amorphous silicon layer 3 has a positive hydrogen concentration gradient toward the p-type amorphous silicon layer 3, and the p-type amorphous silicon layer 3 has a higher hydrogen concentration than the i-type amorphous silicon layer 2.

  In the first embodiment, in addition to the effect of preventing hydrogen diffusion due to the high hydrogen concentration of the p-type amorphous silicon layer 3 corresponding to the window layer on the light incident side, the p-type amorphous silicon layer 3 This also has the effect of reducing the light absorption loss and increasing the generated current.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 shows an H.264 operation according to the second embodiment of the present invention. I. T.A. 2 schematically shows a hydrogen concentration profile in the vicinity of an interface between a p-type amorphous silicon layer and an i-type amorphous silicon layer of a solar cell having a structure.

  As shown in FIG. 5, in the second embodiment, the configuration of the p-type amorphous silicon layer 3 is changed. In the first embodiment, the hydrogen concentration of the entire p-type amorphous silicon layer 3 is increased, whereas in the second embodiment, the i-type amorphous silicon of the p-type amorphous silicon layer 3 is used. Only the front half 31 on the side close to 2 has a high hydrogen concentration, and the rear half 32 returns to a hydrogen concentration equivalent to that of the conventional apparatus.

  In the structure of the second embodiment, the boron (B) doping concentration of the p-type amorphous silicon layer 31 in the first half is relatively low (<1.0 at.%), And the boron (B) doping in the second half 32 is performed. It is effective when the concentration is relatively high (> 2.0 at.%). This is because the structure of the second embodiment can prevent hydrogen diffusion from the i-type amorphous silicon layer to the p-type amorphous silicon layer, as in the first embodiment, but the first half of the p-type amorphous structure. Hydrogen diffuses from the porous silicon layer 31 to the amorphous silicon layer 32 in the latter half. However, since the amorphous silicon layer 32 in the latter half has a high boron (B) concentration, even if a part of boron (B) due to a small amount of diffused hydrogen is inactivated, the influence on the device characteristics can be made relatively small.

Table 3 shows the formation conditions of the second embodiment. As can be seen from this table, the p-type silicon layer 31 and the p-type silicon layer 32 have different B ₂ H ₆ flow rates to form films. The B ₂ H ₆ flow rate was higher in the p-type amorphous silicon layer 32 than in the p-type amorphous silicon layer 31, and the hydrogen dilution amount was higher in the p-type amorphous silicon layer 31. The conditions on the back side were created according to the conditions shown in Table 1. The i-type amorphous silicon layer 2 was formed with a film thickness of 10 nm, and the p-type amorphous silicon layers 31 and 32 were formed with a film thickness of 4 nm.

  Then, the second embodiment and a conventional apparatus were prepared, and the hydrogen concentration profile in the film was measured by SIMS. The result is shown in FIG. FIG. 6 shows the H.I.T. It is a figure which shows the hydrogen concentration profile of the interface part of the p-type amorphous silicon layers 31 and 32 and the i-type amorphous silicon layer 2 which measured the solar cell of the structure by SIMS. Conditions such as measurement are the same as those in the first embodiment.

  From the hydrogen concentration profile measured by SIMS in FIG. 6, a concentration profile similar to the schematic diagram in FIGS. 2 and 5 can be confirmed, and the first half of the p-type amorphous silicon layer on the side close to the i-type amorphous silicon layer. It can be seen that only hydrogen 31 has a high hydrogen concentration, and the latter half 32 has a hydrogen concentration gradient equivalent to that of the conventional apparatus.

  Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 7 schematically shows a hydrogen concentration profile in the vicinity of the interface between the p-type amorphous silicon layer and the i-type amorphous silicon layer of the solar cell having the HIT structure according to the third embodiment of the present invention. is there.

  In the third embodiment, a low hydrogen concentration i-type trap layer 33 having a thickness of about 2 nm is provided as a hydrogen diffusion suppression region in the vicinity of the interface between the p-type amorphous silicon layer 3 and the i-type amorphous silicon layer 2. Is installed. In the third embodiment, hydrogen diffusion from the i-type amorphous silicon layer 2 to the i-type trap layer 33 occurs, but the influence does not reach the p-type amorphous silicon layer.

  Table 4 shows the formation conditions of the third embodiment. The conditions on the back side are the same as the conditions shown in Table 1. The i-type amorphous silicon layer 2 including the i-type trap layer 33 was formed to a thickness of 10 nm, the i-type trap layer 33 was set to 2 nm, and the p-type amorphous silicon layer 3 was formed to a thickness of 8 nm.

  In order to make the hydrogen concentration in the i-type trap layer 33 lower than that in the i-type amorphous silicon layer, the i-type trap layer 33 is not diluted with hydrogen in the third embodiment. There is.

  (1) The substrate temperature at the time of forming the p-type amorphous silicon layer is set higher than that at the time of forming the i-type amorphous silicon layer. (2) The hydrogen dilution amount at the time of forming the p-type amorphous silicon layer is made lower than that at the time of forming the i-type amorphous silicon layer. (3) The film forming pressure at the time of forming the p-type amorphous silicon layer is made lower than that at the time of forming the i-type amorphous silicon layer. (4) RF input power at the time of forming the p-type amorphous silicon layer is made lower than that at the time of forming the i-type amorphous silicon layer.

  A third embodiment and a conventional apparatus were prepared, and the hydrogen concentration profile in the film was measured by SIMS. The result is shown in FIG. FIG. 8 shows the H.264 in the third embodiment. I. T.A. It is a figure which shows the hydrogen concentration profile of the interface part of the p-type amorphous silicon layer 3, the i-type trap layer 33, and the i-type amorphous silicon layer 2 which measured the solar cell of the structure by SIMS. Conditions such as measurement are the same as those in the first embodiment. Conditions such as measurement are the same as those in the first embodiment.

  From the hydrogen concentration profile measured by SIMS in FIG. 8, a concentration profile similar to the schematic diagram in FIGS. 2 and 7 can be confirmed, and it can be seen that hydrogen diffusion from the i-type amorphous silicon layer 2 can be trapped in the trap layer 33. .

  Next, a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 9 schematically shows the hydrogen concentration profile in the vicinity of the interface between the p-type amorphous silicon layer and the i-type amorphous silicon layer of the solar cell having the HIT structure according to the fourth embodiment of the present invention. is there.

  The hydrogen concentration of the i-type amorphous silicon layer 2 in the vicinity of the interface between the p-type amorphous silicon layer 3 and the i-type amorphous silicon layer 2 affects the power generation voltage of the H.I.T. solar cell. It has been found that the output voltage can be improved by increasing the hydrogen concentration in the latter half of the i-type amorphous silicon layer 2 (on the p-type amorphous silicon layer 3 side). The third embodiment described above is in the opposite direction, and hydrogen diffusion into the p-type amorphous silicon layer 3 can be prevented, but the output voltage is slightly reduced. Therefore, in the fourth embodiment, boron (B) is doped into the trap layer 34 having a thickness of about 2 nm. Thereby, hydrogen diffusion into the p-type amorphous silicon layer 3 can be prevented without lowering the output voltage.

  Table 5 shows the formation conditions of the fourth embodiment. The conditions on the back side are the same as the conditions shown in Table 1. The i-type amorphous silicon layer 2 was formed to a thickness of 10 nm, the trap layer 34 was formed to a thickness of 0.5 nm, and the p-type amorphous silicon layer 3 was formed to a thickness of 6 nm.

  The fourth embodiment and a conventional apparatus were prepared, and the hydrogen concentration profile in the film was measured by SIMS. The result is shown in FIG. FIG. 10 shows H.264 in the fourth embodiment. I. T.A. It is a figure which shows the hydrogen concentration profile of the interface part of the p-type amorphous silicon layer 3, the trap layer 34, and the i-type amorphous silicon layer 2 which measured the solar cell of the structure by SIMS. Conditions such as measurement are the same as those in the first embodiment. Conditions such as measurement are the same as those in the first embodiment.

  From the hydrogen concentration profile measured by SIMS in FIG. 10, the same concentration profile as in the schematic diagrams in FIGS. 2 and 9 can be confirmed, and it can be seen that hydrogen diffusion from the i-type amorphous silicon layer 2 can be captured by the trap layer. .

  Next, the H.264 according to the first to fourth embodiments of the present invention described above will be described. I. T.A. Table 6 shows the results obtained by preparing a solar cell device having a structure and a conventional solar cell device, performing thermal annealing at 250 ° C. for 3 hours in the atmosphere, and measuring the change in characteristics.

  As can be seen from Table 6, by providing a hydrogen diffusion suppression region between the p-type amorphous silicon layer and the i-type amorphous silicon layer as in the first to fourth embodiments of the present invention, It was confirmed that the degradation of output characteristics due to high temperature heating could be greatly suppressed. In addition, since the deterioration of output characteristics can be suppressed even when high-temperature heating is performed, a high-temperature fired material can be used as the collector electrode, and the electrode resistance can be reduced.

  Next, the film thickness of the trap layer 33 and the trap layer 44 was changed, and the change in characteristics was examined. First, a solar cell device as a sample was formed by varying the film thickness of the i-type trap layer 33 in the third embodiment. A sample was prepared under the above-described formation conditions except that the film thickness of the i-type trap layer 33 was changed. Each sample was thermally annealed at 250 ° C. for 3 hours in the atmosphere, and the initial characteristics, change rate, and post-anneal characteristics were examined. The results are shown in Table 7 and FIGS. The characteristics were normalized by setting the output of the conventional example without the trap layer 33 as 1. FIG. 11 is a characteristic diagram showing the relationship between the film thickness and the initial characteristics, and FIG. 12 is a characteristic diagram showing the relative output of the characteristics after the heat treatment and the initial characteristics as the rate of change, and the relationship with the film thickness. 13 is a characteristic diagram showing the relative output after heat treatment in relation to the film thickness.

  From Table 6 and FIGS. 11 to 13, it can be seen that when the i-type trap layer 33 is provided, the post-annealing characteristics are improved as compared with the conventional example when the film thickness is 1 nm or more and 5 nm or less. Therefore, the film thickness of the i-type trap layer 33 may be 1 nm or more and 5 nm or less, and more preferably 1 nm or more and 2 nm or less. In addition, this film thickness is a value calculated by forming time for forming a film having a predetermined film thickness and calculating each sample based on the forming time.

  Next, a solar cell device as a sample was formed by variously changing the film thickness of the trap layer 34 doped with boron (B) in the fourth embodiment. A sample was prepared under the above-described formation conditions except that the thickness of the trap layer 34 was changed. Each sample was thermally annealed at 250 ° C. for 3 hours in the atmosphere, and the initial characteristics, change rate, and post-anneal characteristics were examined. The results are shown in Table 8 and FIGS. The characteristics were normalized by setting the output of the conventional example without the trap layer 34 to 1. FIG. 14 is a characteristic diagram showing the relationship between the film thickness and the initial characteristics, and FIG. 15 is a characteristic diagram showing the relative output of the characteristics after the heat treatment and the initial characteristics as the rate of change, and the relationship with the film thickness. 16 is a characteristic diagram showing the relative output after the heat treatment in relation to the film thickness.

  From Table 8 and FIGS. 14 to 16, when the trap layer 34 is provided, it can be seen that when the film thickness is 0.1 nm or more and less than 3 nm, the post-annealing characteristics are improved, and further 0.3 nm or more and 2 nm or less. It can be seen that the characteristics are further improved. Therefore, the thickness of the trap layer 34 is preferably 0.1 nm or more and less than 3 nm, and more preferably 0.3 nm or more and 2 nm or less. In addition, this film thickness is a value calculated by forming time for forming a film having a predetermined film thickness and calculating each sample based on the forming time.

  In the above-described embodiment, the single crystal silicon substrate is used as the crystalline semiconductor substrate. However, the same effect can be obtained by using a polycrystalline semiconductor substrate such as a polycrystalline silicon substrate. In the above-described embodiment, an amorphous silicon layer is used as the amorphous semiconductor film containing hydrogen. However, the present invention is not limited thereto, and amorphous silicon carbide, amorphous silicon germanium amorphous Similar effects can be obtained by using a silicon-based alloy or a semiconductor thin film containing minute crystal grains in the film.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

H. to which this invention is applied I. T.A. It is a schematic sectional drawing which shows the photovoltaic apparatus of a structure. Conventional H.264. I. T.A. It is a schematic diagram which shows the hydrogen concentration profile of the interface vicinity of the p-type amorphous silicon layer and i-type amorphous silicon layer of the solar cell of a structure. H. in the first embodiment of the present invention. I. T.A. It is a schematic diagram which shows the hydrogen concentration profile of the interface vicinity of the p-type amorphous silicon layer and i-type amorphous silicon layer of the solar cell of a structure. H. in the first embodiment of the present invention. I. T.A. It is a figure which shows the hydrogen concentration profile of the interface part of the p-type amorphous silicon layer and i-type amorphous silicon layer which measured the solar cell of the structure by SIMS. H. in the second embodiment of the present invention. I. T.A. It is a schematic diagram which shows the hydrogen concentration profile of the interface vicinity of the p-type amorphous silicon layer and i-type amorphous silicon layer of the solar cell of a structure. H. in the second embodiment of the present invention. I. T.A. It is a figure which shows the hydrogen concentration profile of the interface part of the p-type amorphous silicon layer and i-type amorphous silicon layer which measured the solar cell of the structure by SIMS. H. in the third embodiment of the present invention. I. T.A. It is a schematic diagram which shows the hydrogen concentration profile of the interface vicinity of the p-type amorphous silicon layer and i-type amorphous silicon layer of the solar cell of a structure. H. in the third embodiment of the present invention. I. T.A. It is a figure which shows the hydrogen concentration profile of the interface part of the p-type amorphous silicon layer and i-type amorphous silicon layer which measured the solar cell of the structure by SIMS. H. in the fourth embodiment of the present invention. I. T.A. It is a schematic diagram which shows the hydrogen concentration profile of the interface vicinity of the p-type amorphous silicon layer and i-type amorphous silicon layer of the solar cell of a structure. H. in the fourth embodiment of the present invention. I. T.A. It is a figure which shows the hydrogen concentration profile of the interface part of the p-type amorphous silicon layer and i-type amorphous silicon layer which measured the solar cell of the structure by SIMS. It is a characteristic view which shows the relationship between the film thickness of the trap layer in 3rd Embodiment of this invention, and an initial characteristic. It is the characteristic view which calculated | required the relative output of the characteristic after heat processing, and the initial characteristic as a change rate in the 3rd Embodiment of this invention, and showed it with the film thickness of the trap layer. It is the characteristic view which showed the relative output after heat processing in the 3rd Embodiment of this invention by the relationship with the film thickness of a trap layer. It is a characteristic view which shows the relationship between the film thickness of the trap layer in 4th Embodiment of this invention, and an initial characteristic. It is the characteristic view which calculated | required the relative output of the characteristic after heat processing, and an initial characteristic as a change rate in 4th Embodiment of this invention, and showed it by the relationship with the film thickness of the trap layer. It is the characteristic view which showed the relative output after heat processing in 4th Embodiment of this invention with the relationship with the film thickness of a trap layer.

Explanation of symbols

1 n-type single crystal silicon substrate 2 i-type amorphous silicon layer 3 p-type amorphous silicon layer 4 ITO film 5 collector electrode 6 i-type amorphous silicon layer 7 n-type amorphous silicon layer 8 ITO film 9 collection electrode

Claims (16)

A crystalline semiconductor substrate, a substantially intrinsic amorphous semiconductor thin film layer containing hydrogen provided on the crystalline substrate, and a load containing hydrogen provided on the intrinsic amorphous semiconductor thin film An electronically controlled amorphous semiconductor thin film layer, and the intrinsic amorphous semiconductor thin film layer provided between the valence-controlled amorphous semiconductor thin film layer and the intrinsic amorphous semiconductor thin film layer. And a hydrogen diffusion suppressing region that suppresses hydrogen diffusion from the semiconductor thin film layer to the amorphous semiconductor thin film layer controlled by valence electrons. The hydrogen diffusion suppression region has a hydrogen concentration in the intrinsic amorphous semiconductor thin film layer in the vicinity of the interface between the valence-controlled amorphous semiconductor thin film layer and the intrinsic amorphous semiconductor thin film layer. The photovoltaic device according to claim 1, wherein the photovoltaic device is formed in a region having a higher hydrogen concentration. The hydrogen diffusion suppression region has a hydrogen concentration in the intrinsic amorphous semiconductor thin film layer in the vicinity of the interface between the valence-controlled amorphous semiconductor thin film layer and the intrinsic amorphous semiconductor thin film layer. The hydrogen concentration is higher and the amorphous semiconductor thin film layer controlled by valence electrons is formed in a region doped with impurities for controlling valence electrons of the same type. Photovoltaic device. The hydrogen diffusion suppression region has a hydrogen concentration in the intrinsic amorphous semiconductor thin film layer in the vicinity of the interface between the valence-controlled amorphous semiconductor thin film layer and the intrinsic amorphous semiconductor thin film layer. The photovoltaic device according to claim 1, wherein the photovoltaic device is formed of a trap layer having a lower hydrogen concentration. The photovoltaic device according to claim 4, wherein the trap layer is formed of a substantially intrinsic amorphous semiconductor thin film layer. 5. The photovoltaic device according to claim 4, wherein the trap layer is doped with impurities for controlling valence electrons of the same type as the amorphous semiconductor thin film layer controlled for valence electrons. 6. An n-type single crystal silicon substrate, a substantially intrinsic amorphous silicon layer containing hydrogen provided on the single crystal silicon substrate, and a p containing hydrogen provided on the intrinsic amorphous silicon layer Provided between the p-type amorphous silicon layer, the p-type amorphous silicon layer, and the intrinsic amorphous silicon layer, from the intrinsic amorphous silicon layer to the p-type amorphous silicon layer A photovoltaic device, comprising: a hydrogen diffusion suppression region that suppresses hydrogen diffusion. The hydrogen diffusion suppression region is a region whose hydrogen concentration is higher than the hydrogen concentration of the intrinsic amorphous silicon layer in the vicinity of the interface between the p-type amorphous silicon layer and the intrinsic amorphous silicon layer. The photovoltaic device according to claim 7, wherein the photovoltaic device is formed. The hydrogen diffusion suppression region has a hydrogen concentration higher than the hydrogen concentration of the intrinsic amorphous silicon layer in the vicinity of the interface between the p-type amorphous silicon layer and the intrinsic amorphous silicon layer, and The photovoltaic device according to claim 7, wherein the photovoltaic device is formed in a region doped with a p-type impurity. The hydrogen diffusion suppression region is formed by a trap layer having a hydrogen concentration lower than the hydrogen concentration of the intrinsic amorphous silicon layer in the vicinity of the interface between the p-type amorphous silicon layer and the intrinsic amorphous silicon layer. The photovoltaic device according to claim 7, wherein The photovoltaic device according to claim 10, wherein the trap layer is formed of a substantially intrinsic amorphous silicon layer. The photovoltaic device according to claim 11, wherein the trap layer has a thickness of 1 nm to 5 nm. The photovoltaic device according to claim 11, wherein the trap layer has a thickness of 1 nm to 2 nm. 11. The photovoltaic device according to claim 10, wherein the trap layer is an amorphous silicon layer doped with a p-type impurity. The photovoltaic device according to claim 14, wherein the trap layer has a thickness of 0.1 nm or more and less than 3 nm. The photovoltaic device according to claim 14, wherein the trap layer has a thickness of 0.3 nm to 2 nm.

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