JPS59124772A - Hetero-junction photovoltaic cell of crystal system semiconductor and amorphous semiconductor - Google Patents

Abstract

PURPOSE:To improve conversion efficiency, and to manufacture the photovoltage cell at low cost by joining a unit cell consisting of an amorphous semiconductor with the amorphous semiconductor hetero-junctioned with the single crystal or polycrystalline crystal system semiconductor. CONSTITUTION:K+2C (K=1 or 2 and C is zero or an integer) P type polycrystalline semiconductors 11p and at least each one of P type, I type and N type 2-K+3A (A is an integer) amorphous or crystallite semiconductors 20n are hetero-junctioned HJ, thus forming the unit cell. P type amorphous silicon (P-aSi) 21p, I type amorphous silicon (I-aSi) 21i and N type amorphous silicon (N-aSi) or N type crystallite silicon (N-thetaC.Si) 21n constitute an amorphous unit cell P-I-N joined. A transparent conductive film 10 as an electrode is formed on the semiconductor 21n. The unit cell of the semiconductor 20n absorbs light on the short wavelength side in incident light, and the semiconductor 11p absorbs light on the long wavelength side, thus effectively utilizing light extending over a wide range by the single photovoltaic cell.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a photovoltaic element used in solar cells, detection elements, etc., which is a combination of a single crystal or polycrystalline semiconductor and an amorphous semiconductor.

Prior Art Conventionally, solar cells using semiconductor materials include Si.
In addition to solar cells with homojunction or heterojunction of P-type and N-type 01 crystal or polycrystalline semiconductors such as SGaAs, CdS, CdTe, etc., N-type, ■-type, and P-type Solar cells with two layers of amorphous silicon deposited are commercially available. Furthermore, a solar cell has been proposed in which high voltage output can be extracted from a single element by stacking multiple intermediate cells each deposited with N-type, ■-type, and P-type a-8I layers. .

In order to manufacture solar cells at low cost, it is necessary to make them thinner, and amorphous silicon solar cells have the advantage of being only 0.5i1m thick compared to 300/1m for single crystal silicon. , as shown in Fig. 1, the area surrounded by the gear collection efficiency curve a-8i of the amorphous silicon solar cell for each wavelength of incident light is approximately half the area surrounded by the carrier collection efficiency curve c-8i of the single-crystal silicon solar cell. As a result, the conversion efficiency of amorphous silicon solar cells is lower than that of single crystal silicon solar cells. In other words, in Figure 1, the horizontal axis shows the wavelength λ[, #m], and the vertical axis shows the carrier collection efficiency η [%], and the carrier collection efficiency curve c-8i of the single-crystal silicon solar cell has a relatively long wavelength. In contrast, the carrier collection efficiency curve a-3i of an amorphous silicon solar cell is biased toward relatively short wavelength light. Therefore, the amorphous silicon solar cells that have been put into practical use cannot utilize incident light as effectively as crystalline semiconductor solar cells, so their conversion efficiency is as low as 8-9%. .

Therefore, recently, for sunlight with a wide spectrum,
A-3i solar cells having a multilayer unit cell structure in which wavelength-divided unit cells are stacked to have the maximum value of carrier collection efficiency for each wavelength width in a certain range are also being studied. For amorphous semiconductors, the optical band gap, which influences the carrier collection efficiency for each wavelength, can be changed by changing the type of gas supplied or the mixing ratio thereof during manufacturing. As amorphous semiconductors for short wavelengths, hydrogenated amorphous silicon carbide a-3iC:11,
Hydrogenated amorphous silicon nitride a-8iN:11, hydrogenated amorphous silicon germanium a-8i Ge:H, hydrogenated 4-amorphous silicon tin a-8i Sn:@, etc. are used for long wavelengths. However, even in these amorphous solar cells with a multilayer unit cell structure, as mentioned above, the amorphous semiconductor cannot absorb long wavelength light as well as the crystalline semiconductor due to its woody nature. It is not possible to fully compensate for the shortcomings.

Purpose of the Invention The present invention provides an amorphous semiconductor unit cell that absorbs a large amount of incident light by joining an intermediate cell made of an amorphous semiconductor to an amorphous semiconductor heterojunctioned with a single-crystalline or polycrystalline crystalline semiconductor. A single photovoltaic element can effectively utilize a wide range of light by absorbing short-wavelength light, and the crystalline semiconductor absorbs long-wavelength light that cannot be absorbed by amorphous semiconductor unit cells. To provide a photovoltaic element that has improved conversion efficiency than a solar cell made of a crystalline semiconductor alone or an amorphous semiconductor alone, and that can be manufactured at a lower cost than a stacked solar cell made only of a crystalline semiconductor. It is in.

EXAMPLES Hereinafter, examples of the present invention will be described in detail. Figure 2 (A)
1 is a configuration diagram of the first embodiment of the present invention, 1 is an aluminum electrode, 11r) is a P-type polycrystalline silicon substrate (P
-Poly-8i), 2On is N-type amorphous silicon (N-aSi) or N-type microcrystalline silicon (N
-, &C-8i), which is a P-type polycrystalline semiconductor 11p
and an amorphous or microcrystalline semiconductor 2On are formed into a heterojunction HJ to form a unit cell. 21p is P-type amorphous silicon (P-a Si ), 21+ is ■-type 7-E-rufus silicon (] -a Si >, 21
n is N-type amorphous silicon (N-aSi> or N
type microcrystalline silicon (N-, pc-si), 21
p121i and 21n constitute a P-I-N junction amorphous unit cell. Furthermore, a transparent conductive film 10 as an electrode is formed on the N-type semiconductor 21n. The charge-controlled microcrystalline semiconductor described above has optical properties similar to those of an amorphous semiconductor, and electrical properties similar to those of a crystalline semiconductor. The embodiment of FIG. 2(A) is K12C (K=1 or 2, C
is zero or an integer) single crystal or polycrystalline semiconductors and at least one each of P type, I type and N type.
In a photovoltaic device with a heterojunction of +3A (A is an integer) amorphous semiconductors, K=1, C=O1
This is a case where A=1, a crystalline semiconductor and an amorphous semiconductor are heterojunctioned to form an intermediate cell, and a unit cell of an amorphous semiconductor is further junctioned. These amorphous semiconductors 2On, 21r+, 21
i, 21n and the thickness of the transparent conductive film 10 are each 3000. FIG. 2(B) is an energy band diagram of the photovoltaic device of FIG. 2(A). In the same figure, E (
Jol is the forbidden band width of the polycrystalline silicon semiconductor 11p and is approximately 1
．． 1 [eVl, and E Oal is the forbidden band width of amorphous silicon semiconductor, which is approximately 1.7 to 1.8 [eVl].
Vl, and E(Ial > F(Icl). In the same figure, "C" is the lower limit of the conduction band, "" is the Fermi level, and EV is the upper limit of the valence band. indicates the level of

In FIG. 3, the horizontal axis is the wavelength λ [Pm] of the incident light, and the vertical axis is the carrier collection efficiency η [rel ·U], and shows the carrier collection efficiency of the solar cell with respect to the change in the wavelength λ of the incident light. In the same figure, a dashed-dotted line Sun-8 indicates the spectrum curve of sunlight. In addition, each wavelength λ[)Lm ] of light incident on an amorphous unit cell with a large forbidden band width
The carrier collection efficiency η[rel ·ul with respect to the current value is as shown by the solid line a-3i in the same figure.

Next, the polycrystalline semiconductor 11p, which has a small forbidden band width, absorbs the light on the long wavelength side that has passed through the amorphous semiconductor, and the carrier collection efficiency of the polycrystalline semiconductor is expressed by the dotted line poly-
As shown in 8i. As a result, Sung developed a single photovoltaic device that was made by bonding a unit cell made of an amorphous semiconductor to an amorphous semiconductor that was heterojunctioned with a crystalline semiconductor to effectively utilize a wide range of light from short wavelengths to long wavelengths. -8-' I can do that.

FIG. 4 is a diagram showing actually measured values of the T-■ characteristic of the photovoltaic device shown in FIG. 2(A).

In the figure, the horizontal axis shows the output voltage Vout[V] of the photovoltaic device in FIG. 2(A), and the vertical axis shows the output current 1out[mΔ/(Tlll) of the photovoltaic device.

The conversion efficiency of the photovoltaic element shown in FIG. 2(A), determined from the IV characteristics shown in the same drawing, was 11 to 12%, which is much higher than the 8 to 9% of published amorphous solar cells.

FIG. 5(A) is a configuration diagram showing a second embodiment of the present invention, in which a P-N junctioned crystalline semiconductor constitutes a unit cell, and a P-1-N junctioned amorphous semiconductor The semiconductor groups constitute first and second unit cells, and the intermediate cell of these crystalline semiconductors and the 181 of the amorphous semiconductor group constitute the first and second unit cells.
1 unit cell or a heterojunction. In the figure, 2 is a substrate made of a thin plate of inorganic solid such as metal, glass, or reramic, or a film of organic solid such as polyimide. 1 is an ohmic electrode formed on the substrate 2, and 1111 is a P deposited on the ohmic electrode.
The type crystalline gallium arsenide GaAS 111n is N-type crystalline gallium arsenide GaAs, and these P-type crystalline gallium arsenide and N-type crystalline gallium arsenide are PN-junctioned to form the unit cell 11. 21+1 is P-type amorphous silicon stacked on N-type crystalline gallium arsenide 1n, 211 is ■-type amorphous silicon, 21n
is N-type amorphous silicon, and these amorphous silicones 21p, 21i, and 21n constitute the first unit cell 21. N-type crystalline gallium arsenide 11n and the first
The P-type amorphous silicon 21r+ forming a part of the amorphous unit cell 21 is in a heterojunction 1-IJ. Further, on the amorphous first unit cell 21, P-type amorphous silicon carbide (a-3i C)2
2p, I-type amorphous silicon carbide 22i, and N-type amorphous silicon carbide 22n constitute a second amorphous intermediate cell 22. A transparent conductive film 10 as an electrode is formed on the N-type amorphous silicon carbide 22n. The embodiment of FIG. 5(A) is K+2C (K=1 or 2
, C is zero or an integer) single-crystal or polycrystalline crystalline semiconductors and 2-+3△ (△ is an integer) amorphous semiconductors including at least one each of P type, ■ type, and N type. In the bonded photovoltaic device, K=2, C-0
, Δ-2, and one crystalline semiconductor unit (f
This is a case where an f cell and two amorphous semiconductor intermediate cells are formed, and the crystalline semiconductor of the formed crystalline intermediate cell and the amorphous semiconductor of the formed amorphous unit cell are heterojunctioned.

FIG. 5(R) is an energy band diagram of the photovoltaic device shown in FIG. 5(Δ). In the figure, "gcl is the forbidden band width of the unit cell 11 of crystalline gallium arsenide, which is approximately 1.4 [f
3V], E gal is about 1.8 [eVl at the forbidden band width of the first amorphous intermediate cell 21, and F! ]a
2 is the forbidden band width of the second amorphous unit cell 22, which is approximately 2
．． 0[eVl, and the relationship between the forbidden band width is Fg
a2 > EOal > Eoc111-. In addition, in the figure, Ec, Ff, J: and EV are the same as in FIG. 2(B). The second amorphous unit cell 22 whose forbidden band width is the maximum E aa2
absorbs light with a relatively short wavelength among the incident light. The first amorphous unit cell 21 having the second largest forbidden band width E gal absorbs light having a relatively long wavelength that has passed through the second amorphous intermediate cell 22 . Furthermore, the crystalline unit cell 11 with the smallest forbidden band width E oa2 absorbs the long wavelength light that has passed through the first amorphous unit cell 21 . As a result, the crystalline unit cell 11 and the first amorphous unit cell 21 are heterojunctioned, and the second amorphous unit cell 22 is further joined onto the first amorphous unit cell 21 to form a single photovoltaic power. The device can absorb light with a wide range of wavelengths from short wavelengths to long wavelengths.

FIG. 6 is a configuration diagram showing a third embodiment of the present invention, in which a group of crystalline semiconductors connected to a P-N junction sequentially constitute first to third crystalline intermediate cells, and P-1-N junction amorphous semiconductors 012- constitute first to third amorphous unit cells in sequence, and form a third crystal system. 11th cell The crystalline semiconductor on the surface of cell 0 and the amorphous semiconductor on the surface of the first amorphous unit cell 21 are in a heterojunction. In the figure, reference numeral 1 denotes a stainless steel substrate which also serves as an electrode. 11 is a first crystalline unit cell of P-N junction; 12
is the second crystalline unit cell of the P-N junction, 13 is the third crystalline intermediate cell of the P-N junction, 21 is the first amorphous unit cell of the P-T-N junction, and 22 is the P-N junction. -1-N junction second amorphous unit cell; 23 is P-T-N junction third amorphous unit cell; 10 is a transparent conductive film forming an electrode. The crystalline semiconductor on the surface of the third crystalline unit cell 130 and the amorphous semiconductor on the surface of the first amorphous unit cell 210 form a heterojunction HJ. Furthermore, the first to third crystalline intermediate cells are each composed of germanium (Ge), silicon (Si), and gallium arsenide (GaAs) semiconductor groups, and the forbidden band widths of these intermediate cells are as follows. , [”gc1=0.7
[c Vl, F(]c2 = 1.1 [e Vl and Egc3-1.4 [eV].Furthermore, the first to third amorphous unit cells are each made of amorphous silicon germanium (a-8i -Ge)
, amorphous silicon (a-8i) and amorphous silicon carbide (a-8i C), and the forbidden band width of each of these unit cells is Foa
l = 1.6[e Vl , Eaa2 = 1.8[
e Vl and J: and ``ga3 = 2.0 [e Vl.

The third amorphous unit cell 22 having the largest bandgap absorbs light with a relatively short wavelength of the incident light, and the second amorphous unit cell 22 having the second largest bandgap absorbs light with a relatively short wavelength of the incident light. The amorphous shell (absorbs light with a relatively long wavelength that has passed through the FF cell 23.
amorphous unit cell, a third crystalline unit cell, a second
In the order of the first crystalline unit cell and the first crystalline unit cell, light having a relatively short wavelength is absorbed in order, and in the later unit cells, light having a relatively long wavelength is absorbed. In this way, the single photovoltaic element described above can absorb light of a wide range of wavelengths from short wavelengths to long wavelengths.

Figure 7 (Δ) shows that, in order to increase the absorption of incident light within a photovoltaic element, countless tiny tetragons are formed on the surface of a crystalline semiconductor substrate, an inorganic solid thin plate, or an organic solid film substrate. It is a model diagram in which unevenness made of a body is formed. The figure (B) shows that by providing the unevenness shown in the figure (△), light absorption is increased by optical multiple reflection and refraction between the incident light and the pyramid surface of the surface, and the crystalline semiconductor of the present invention and the amorphous The conversion efficiency of the photovoltaic element can be improved by combining a structure in which a semiconductor is heterojunctioned with an amorphous t1'i cell, or a structure in which a crystalline intermediate cell and an amorphous unit cell are heterojunctioned. can be done. In the same figure (R), 10 is a transparent conductive film, 21 is an amorphous semiconductor, 11 is a crystalline semiconductor, and incident light is transmitted to the interface between the transparent conductive film 10 and the amorphous semiconductor 21, and the interface between the amorphous semiconductor 21 and the crystalline semiconductor 11. As shown by the solid line, multiple reflections occur one after another, and the absorption of light can be increased by confining the light.

According to the photovoltaic device of the present invention, light on the shorter wavelength side of incident light is absorbed by the amorphous semiconductor unit cell, and furthermore, these amorphous semiconductors absorb light on the shorter wavelength side. A single photovoltaic element can absorb a wide range of light from short wavelengths to long wavelengths by absorbing the long-wavelength light that has been transmitted through a crystalline semiconductor or crystalline unit cell. Therefore, it has a higher conversion efficiency than a solar cell made of a crystalline semiconductor alone or an amorphous semiconductor, and can be manufactured at a lower cost than a stacked solar cell made of a crystalline semiconductor alone, and is highly effective. Furthermore, since the photovoltaic element of the present invention is made of laminated materials having different spectral sensitivity characteristics, it can also be used as a photodetecting element that also detects light of a specific wavelength.

[Brief explanation of drawings]

Figure 1 shows the wavelength λ[Pml (horizontal axis) of incident light 16- and the carrier collection efficiency ηL of a conventional crystalline solar cell 1-3i) and an amorphous solar cell (a-8t).
%] (l-axis), FIG. 2 (A) and (B) are respectively a block diagram and an energy band diagram of the first embodiment of the photovoltaic device of the present invention, and FIG. is the second
In the configuration of the embodiment shown in Figure (A), an amorphous semiconductor (
The relationship between the incident light λ[,1,1ml (horizontal axis) and the carrier collection efficiency η[rel・'1] (vertical axis) to the solid line curve a-8t) and the polycrystalline semiconductor (dotted line curve poly-8i) A diagram showing the relationship, FIG. 4 is the IV characteristic of the photovoltaic device of the example shown in FIG. Pictorial diagram showing the output current Iout [mA/cT11]) of the element, No. 5
Figures (△) and (B) are the configuration diagram and energy band diagram of the second embodiment of the photovoltaic device of the present invention, respectively, and Fig. 6 is the configuration of the third embodiment of the photovoltaic device of the present invention. figure,
FIGS. 7(Δ) and 7(B) are a model diagram and an operation explanatory diagram, respectively, in which a texture pattern that increases the absorption of incident light is formed on the substrate of the photovoltaic device of the present invention. 1... Electrode (ohmic electrode or conductive substrate), 2
...Inorganic solid thin plate substrate or organic solid film substrate, 11.12.13...Crystalline semiconductor unit cell, 11p, 11n...Crystalline semiconductor, 21.22
．． 23...Amorphous semiconductor unit cell, 2On,
21p, 21i, 21n, 22rl, 221.22
n...Amorphous semiconductor, E (IC1, EOC2,
E(IC3...The forbidden band width of a crystalline semiconductor or a unit cell of a crystalline semiconductor, E(Ial, Ega2, Fga
3-...bandgap width of unit cell of amorphous semiconductor, H
J: Heterojunction between a crystalline semiconductor and an amorphous semiconductor. Agent: Hiroshi Nakai, Patent Attorney - 1 drawing - No change to the drawing (no change in content) 1 [μm] 0 1.2 24 3.6
Procedural document (spontaneous) January 1980 310 Commissioner of the Japan Patent Office 1981 Special IT Application No. 23197 2 Title of the invention Junction photovoltaic device between a crystalline semiconductor and an amorphous semiconductor 3 , Relationship with the case filed by amendment Patent application by Keihiro Hamayo, 3-17-4 Minamihanayashiki, Yonishi City, Hyogo Prefecture (
4. Agent address: November 5, 1 Nutagawa 2-chome, Osaka 532, Date of amended order Voluntary procedure Main gate of Tani 11 (Voluntary) 1980/1/1980 Patent Application No. 23/1197 2, Name of the Invention Peter Junction Photovoltaic Element of Crystalline Semiconductor and Amorphous Semiconductor 3, Relationship with Corrected Dimensions 1'1 Patent Application Nishiichi Minami for Hyogo Prefecture Hanayashiki 3-17-4 Keihiro Hamayo (and 2 others) 4, with agent Address 2-1-1 Tanyo, Yodoyo-ku, Osaka 532
No. 1 No. 7, the statement of contents of the amendment is amended as follows. (1) On page 17, line 1, next to “de・kiru.”
Since the above-mentioned element has a structure in which materials r1 with different spectral sensitivities are stacked in series, it is possible to use special color filters by utilizing the different spectral sensitivities of each cell that makes up the element. Even without it, it can be used as a light detection element such as a color sensor. For example, the element shown in Figure 5 (Δ) can have independent spectral sensitivities for the three primary colors of light, blue, green, and red, and can also detect intermediate colors by combining these outputs. Therefore, it can be used as a golden sensor. Compared to the Golden Sensing System, which uses color filters, this method has an advantage in that it is possible to detect colors even at points, and when integrated, the degree of integration can be increased. Insert -1. (2) On page 17, line 16, after "I'm there," insert "By utilizing the unique spectral sensitivity of each cell that makes up one element, there is no need to use a special color filter." do. (3) On page 17, line 16, after "detect", add "like color sense ()" by 1Φ. 346-

Claims (1)

[Claims] 1 K+20 (K=1 or 2, C is zero or an integer) medium-crystalline or polycrystalline crystalline semiconductors and 2- containing at least one each of P type, I type, and N type; +3A (A
is an integer) amorphous semiconductors in a heterojunction. 2. The photovoltaic device according to claim 1, wherein one or more of the amorphous semiconductors is a charge-controlled microcrystalline semiconductor. 3. The photovoltaic device according to claim 1, wherein the crystalline semiconductor is used as a substrate, and a crystalline semiconductor or an amorphous semiconductor is deposited on the substrate. 4. The photovoltaic device according to claim 1, wherein the crystalline semiconductor is deposited on a substrate of an inorganic solid thin plate or an organic solid film. 5. The stacked photovoltaic device according to any one of claims 1 to 4, wherein the crystalline semiconductor and the amorphous semiconductor are heterojunctioned to form a unit cell. 6 The crystalline semiconductor and the amorphous semiconductor each form a unit cell, and the crystalline semiconductor of the formed crystalline unit cell and the amorphous semiconductor of the formed amorphous unit cell are heterojunctioned. Stack type photovoltaic device according to any one of Items 1 to 4. 7. The crystalline semiconductor is composed of a plurality of intermediate cells, and the forbidden band width of each unit cell is F! when viewed from the direction of incident light. ]CI
,E(102,·,Egcn-1,Egcn (E!
ICn-1)Egcn) Any one of claims 1 or 3 to 6 stacked in the following order:
The photovoltaic device described in . 8 The amorphous semiconductor is composed of a plurality of intermediate cells, and the forbidden band width of each unit cell is E when viewed from the direction of incident light.
oal, F oa2. ..., E 0an-1,F
(tan(E(Jan-1>Fgan)) The photovoltaic element according to any one of claims 1 to 7, which is stacked in the order of (tan(E(Jan-1>Fgan)). The photovoltaic device according to claim 3, wherein the photovoltaic element is formed with a textured pattern that increases the absorption of light. 5. The photovoltaic device according to claim 4, wherein the photovoltaic device is formed with a pattern of increasing texture.