JPH01773A - photovoltaic element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a photovoltaic device used as a solar cell or an optical sensor, and particularly to a photovoltaic device formed by laminating thin film semiconductors.

[Conventional technology] Solar cells use inexhaustible sunlight as an energy source, have little impact on the environment, and do not lose efficiency even on a small scale.
Moreover, since it is easy to maintain, it is expected to be used as a next-generation power source, especially as a distributed power source.

Among the photovoltaic elements used for solar power generation, St and GaA
A conversion efficiency of over 20% has been obtained in an element using a single crystal of s. However, these devices are expensive to manufacture, and the price of the resulting power is significantly higher than that of other power generation means, so they have not become widespread.

On the other hand, as photovoltaic elements that can be manufactured at low cost, amorphous silicon pin type elements, Schottky type elements,
Examples include thin film photovoltaic devices such as Cd5-CdTe heterojunction devices. As an example, an amorphous silicon Luminous n-type device is shown in FIG.

In FIG. 2, 22 is an n-type thin film semiconductor layer mixed with P, 23 is a thin film semiconductor layer not mixed with impurities, and 24 is an n-type thin film semiconductor layer mixed with P.
2 is a p-type Fit film/half-film conductor layer mixed with 2, and these are sequentially provided on a metal substrate 21. The photocurrent generated by the photons passing through the transparent conductive layer 25 is
Current is collected to a current collecting electrode 26 via a transparent conductive layer 25.

In the case of such photovoltaic devices, although it is expected that the manufacturing cost of the device itself will be lower, the conversion efficiency η has not reached more than 10% on a practical scale, and the installation cost is also low. The cost is relatively high, and in the end it has not been possible to reduce the price of electricity sufficiently.

In order to improve this current situation, various improvements have been made to increase the conversion efficiency η of thin film photovoltaic elements.

One of the improvement plans is to replace the n-type or p-type thin film semiconductor provided on one or both surfaces of the thin film photovoltaic element with a thin film semiconductor layer (temporarily referred to as layer A) containing an impurity element and the impurity element. A layer in which a thin film semiconductor layer having a different concentration, a different impurity element, or a thin film semiconductor layer (temporarily referred to as layer B) in which no impurity element is mixed than the thin film semiconductor layer mixed with the A layer,
It is a photovoltaic element that is made into a laminated thin film semiconductor by depositing layers (B layer, A layer, B layer, etc.). In the above, the thickness of one of the thin film semiconductor layers is often 100 Å or less. Further, each thin film semiconductor layer may be different from each other, for example, A layer, B layer, 0 layer, D layer, etc., as long as it functions as an element.

FIG. 1 shows an example in which this improved proposal was applied to an a-Si:)I photovoltaic device. Here, 1 is a metal substrate, such as a stainless steel plate with a polished surface. 2 is a thin film semiconductor layer of a-3t:H with a thickness of 50 mm and made n-type by mixing PH3 during film formation. 3 is a thin film semiconductor layer of a-Si:H with a thickness of 50 mm without mixing PH during film formation.

4 is a-5t:H thickness 500 without mixing impurities
There are 0 semiconductor layers. 5 is a 50-layer thin film semiconductor layer of a-3t:H made p-type by mixing B and H6. 6
is a 50 mm thick thin film semiconductor layer of a-3t:H without 82H6 mixed therein. 7 is a transparent conductive layer, for example, an ITO film or the like is used. Reference numeral 8 represents a current collecting electrode, and silver or the like is used, for example.

With the above configuration, the short circuit current (I sc
) for a while. This is because in the device shown in FIG. 2, photons absorbed in the n-type thin film semiconductor layer 22 and the p-type thin film semiconductor layer 24 can hardly generate electrons or holes, whereas in the device shown in FIG. It is presumed that this is because electrons and holes can be generated more effectively in the n-type thin film semiconductor layer 2 and p-type thin film semiconductor layer 5.

However, even in the case of the device shown in FIG.
oc) and fill factors (F, F,) were not sufficient, and the resulting conversion efficiency q could not be improved significantly. In addition, when applying a reverse bias voltage to the device and using it as a photosensor, the dark current σd (
The smaller the diode saturation current (corresponding to the saturation current of the diode) is, the better the ratio (S/N ratio) to the photocurrent can be obtained, and the range of light intensity that can be used as a photosensor will be expanded.

However, at present, the dark current σd is large and does not fully meet practical requirements.

[Problem to be solved by the invention 1 As stated above, in the conventional thin film photovoltaic device, the short circuit current (I ic ) is small, so the conversion efficiency η
is low, and even in the improved plan, the open circuit voltage (V oc)
and fill factor (F, F,) were not sufficiently improved, and the dark current σd was large when a reverse bias voltage was applied, so the S/N ratio as an optical sensor was low.

The present invention solves the above problems of the conventional thin film photovoltaic device, and reduces not only the short circuit current (RIC) but also the open circuit voltage (V
oc) and fill factor (F, F,), and the resulting conversion efficiency η to a value that is practical for solar cells. A further object of the present invention is to reduce the dark current of a thin film photovoltaic element when a reverse bias voltage is applied, and to improve the S/N ratio as a photosensor.

[Means for Solving the Problems] The present invention provides a thin film semiconductor having a thickness of 1 to 1 p-type or n-type by mixing impurity elements on one or both surfaces of the thin film semiconductor during deposition.
A thin film semiconductor with a thickness of 00 Å or less, a thin film semiconductor with a thickness of 100 Å or less in which an impurity element with a concentration different from the above impurity was mixed during deposition, and a film with a thickness of 10.0 Å or less in which an impurity element of a different type than the above impurity element was mixed during deposition. thin film semiconductors,
Alternatively, in a photovoltaic element formed by repeatedly depositing at least one type of thin film semiconductor of 100λ or less in thickness without mixing impurity elements at least twice, the laminated thin film semiconductor is made of silicon. The hydrogen content of the thin film semiconductor is 1.
The gist of the photovoltaic device is that it is a photovoltaic device characterized by having an atomic ratio of at least 10 atomic ratios and no more than 10 atomic ratios.

[Function] As a result of intensive study on the manufacturing method and manufacturing conditions of an element having silicon as a main constituent element and having the structure as shown in FIG.
It has been found that the hydrogen content in an n-type or p-type laminated thin film semiconductor greatly influences the characteristics of a photovoltaic device. The present invention has been made based on this fact.

That is, in the present invention, for example, as in the element shown in FIG. 1 of the improvement plan described in the prior art, a thin film semiconductor layer mixed with an impurity element and a thin film semiconductor layer mixed with the impurity element have different concentrations. For photovoltaic elements that are made into a laminated thin film semiconductor by repeatedly depositing thin film semiconductor layers with different impurity elements or with no impurity elements mixed, the hydrogen content in the thin film semiconductor layer is further reduced. The atomic ratio is 1 to 10.

By forming a layered structure, the short circuit current (I sc ) is improved as described in the conventional technology, and furthermore, by setting the hydrogen content in the thin film semiconductor layer to an atomic ratio of 1 to 10, the open circuit voltage (VOC) and The fill factor (F, F,) increases. This is because the density of electrons and holes in the laminated n-type and p-type semiconductor layers increases, and an electric field is effectively applied to the i-type semiconductor layer.

(Experiments for Detailed Explanation of the Present Invention) Hereinafter, the effects of the present invention will be specifically explained based on experimental results.

(2) Sample Preparation Method and Apparatus Experimental samples were prepared using the apparatus shown in FIG. This device is a hydrogen radical CVD (HR-CVD) device that produces a functional deposited film by reacting a raw material gas containing at least the constituent elements of the functional deposited film and a halogen element with hydrogen radicals.
This is an example of an apparatus for realizing a functional deposited film production method called method D). The HR-CVD method was used because the hydrogen content in the film can be controlled over a wide range, making it easier to demonstrate the effects of the present invention.

In FIG. 3, 31 is a vacuum chamber, which is evacuated by a vacuum pump. A substrate holder 32 is provided in the vacuum chamber 31, and a substrate 33 is fixed onto the substrate holder 32. The base 33 can be heated to a desired temperature by a heater provided within the base holder 32. In addition, the vacuum chamber 31 includes a thick quartz glass tube (outer tube) 34 and a thin quartz glass tube (inner tube).
35 are concentrically connected, and a gas containing hydrogen and a raw material gas for film formation are introduced from the rear end of each. The introduced gas containing hydrogen and the raw material gas for film formation are decomposed and reacted by microwave power of 2.45 GHz applied through the metal applicator 36, and a thin film semiconductor is deposited on the substrate 33. do. Using this apparatus, a 3 ffl thin film semiconductor was manufactured under the manufacturing conditions shown in Table 1. The reason why X is shown in Table 1 is because the experiment was conducted by changing this value.

■Explanation of the effects of laminating membranes Experimental In order to examine the effects of laminating membranes, the following samples were prepared using the apparatus described in (■).

500 silicon nitride layers (hereinafter abbreviated as SiN layers) were deposited on a Corning Co., Ltd. No. 7059 glass substrate whose surface was coated with an ITO film by glow discharge decomposition using SiH4 and NH3 as source gases. On this SiN layer, the first
Under condition A in the table, x = 160W and the n-type silicon layer is
00 people deposited, then under condition B with x=160W and n
A mold silicon layer of 3μ was deposited. Furthermore, 5 layers of SiN are added again.
After depositing 0.00 ml of the sample, an A1 film was deposited on the surface to serve as a surface electrode and a sample (N-1).

Also, instead of the n-type silicon layer, X÷
Sample (p-i) was prepared in the same manner as sample (N-1) except that 300 p-type silicon layers were deposited at 160 W.

Next, after depositing 500 Sin layers on Corning Co. No. 7059 glass coated with an ITO film, under condition A, x =
25 n-type silicon layers were deposited at 160 W, then 25 n-type silicon layers were deposited under condition B with x = 160 W, 25 n-type silicon layers were deposited again, and then n
The process of depositing a mold silicon layer by 25 people was repeated 12 times, resulting in a total of 600 laminated thin film semiconductors. Continue, n
After depositing a mold silicon layer of 3 μm and depositing 500 SiN films again, an Afl film was deposited on the surface to serve as a surface electrode and was used as a sample (N-2).

Also, instead of n-type silicon, x = 1 under condition C in Table 1.
Sample (P-2) was prepared in the same manner as sample (N-2) except that 25 people each deposited a p-type silicon layer at 60 W.

Similarly, the thickness L per layer is changed to 50, 100, and 150 people instead of 25 people, and the n-layer and i-layer or the p-layer and i-layer are repeated 6 times, 3 times, and 2 times, respectively. sample (N
-3) and (P-3).

(N-4) and (P-4), (N-5) and (P-5)
was created.

Using each sample prepared in this way, Time
Of Flight (T OF ) method measurement was performed. Figure 4 shows the setup for this measurement.
The case where N-4) or (P-4) is used is shown. The measurement setup for other samples is similar.

Here, 41 is a glass substrate, 42 is a coated transparent conductive layer of ITO film, and 43 and 47 are SiN layers. SiN
The layer is inserted to prevent injection of electrons and holes from the electrode. 44 is an n-type or p-type thin film semiconductor layer, 45
and 46 are i-type semiconductor layers. Note that the last i-type layer in the laminated thin film semiconductor layer is under the same conditions as the subsequently deposited i-type layer, so it is not distinguished in the figure.

A sample in which the laminated thin film semiconductor is composed of an n-type layer and an i-type layer (
The measurement procedure will be explained for cases N-1) to (N-5). First, in the dark, the IT film was placed between the ITO film 42 and the A1 film 48.
Immediately after applying a voltage pulse such that the O film 42 is positive, pulsed dye laser light excited by a nitrogen laser is incident from the substrate glass 41 side. Since the wavelength of the incident laser light is as short as 460 nm, most of the light is absorbed in the laminated thin film semiconductor (n-type layer of samples (N-1) to (N-5)). Holes generated in this portion drift toward the Afl film 48 due to the electric field, and current flows to the external circuit. By integrating this current, the number of holes flowing through the film can be calculated. If the holes generated in the laminated thin film semiconductor are recombined immediately, the integrated current value Q will decrease, and the degree of hole recombination in the laminated thin film semiconductor can be evaluated.

On the other hand, in the case of samples (p-B to (P-5)) in which the laminated thin film semiconductor is composed of a p-type layer and an i-type layer, the laminated thin film semiconductor is The degree of electron recombination in semiconductors can be similarly evaluated.

Table 2 shows the relative values of the current integrated value Q for each sample. Samples (N-1) to (N-5) and (
In p-t) to (P-5), it is clear from the graph that the total layer thickness of the n-type layer or p-type layer of the laminated thin film semiconductor (thickness of one layer LX < number of repetitions) is 300 people. They are all aligned. Further, the current integration point in the single-layer samples (N-1) and (P-1) was set as the reference for Q (1,0).

As can be seen from Table 2, as the number of repetitions increases, the current integration point Q increases.

In particular, a sample (N-2
) to (N-5) and (P-2) to (P-5), the current integrated value Q (relative value) is 5 or more, and the laminated thin film semiconductor has n
It has been found that recombination of holes and electrons is significantly reduced both when using a p-type semiconductor and when using a p-type semiconductor.

In addition, samples in which the thickness L of one layer exceeds 100 people (
For samples (N-5) and (P-5), samples (N-2) to (N-
4) and (P-2) to (P-4), the improvement is only slight.

The above results show that, for example, when a laminated thin film semiconductor is used as the n-type layer of a pin-type photovoltaic element, the rate at which holes generated in the laminated thin film semiconductor or in the i-type layer near the laminated thin film semiconductor recombine decreases, and the short-circuit photocurrent Is of the photovoltaic element
This shows that it contributes to an increase in c. Similarly, when a laminated thin film semiconductor is used for the p-type layer, the rate at which electrons generated in the laminated thin film semiconductor or in the i-type layer near the laminated thin film semiconductor recombine decreases, resulting in an increase in XSC. This shows that it contributes to

The mechanism by which this effect occurs is thought to be due to a change in the distribution of electrons or holes at the recombination level in the n-type layer or p-type layer in the laminated thin film semiconductor, particularly in the portion adjacent to the i-type layer. Therefore, considering the above mechanism, if L is 100 Å or less, the same effect can be expected even if the number of repetitions is two.

From the above experimental results and considerations, when using a laminated thin film semiconductor as a p-type layer or an n-type layer of a photovoltaic element, the thickness L of one layer should be 100 Å or less, and the number of repetitions should be 2 or more. It can be seen that the tsc of the photovoltaic device can be increased.

(2) Experiment to explain the effect of hydrogen content First, in order to demonstrate that the hydrogen content in the film can be controlled by the HR-CVD method described in (2), the following experiment was conducted. St wafer not doped with impurities (
Using a substrate (with a thickness of 500 μm) as a substrate, an n-type layer, an i-type layer, and a p-type layer with a thickness of 1 μm were fabricated on the substrate under conditions A, B, and C in Table 1, with the microwave discharge power X being 60 W. , respectively as samples (N-6), (I-6), and (P-6).

Similarly, the microwave power X is aow, to.

Samples (N-
7) to (N-11), (I-7) to (I-11), and (P-7) to (P-11) were produced.

Samples (N-6) to (N-1) prepared as above
1), (I-6) to (I-11), and (P-6) to (
P-11) was subjected to a Fourier transform infrared absorption (FTIR) device, and the absorption spectrum of 2000 cm-'~
The absorption intensity of the 5i-H stretching mode existing in the region of 2100 cm-' was measured, and the hydrogen content was calculated. The results are shown in Table 3.

As is clear from Table 3, as the microwave power increases, the hydrogen content increases.

This shows that the hydrogen content can be controlled by microwave power.

Next, samples for evaluating the conductivity of the multilayer film when the hydrogen content was changed were prepared in the following manner. Five n-type layers were formed on a Corning Co., Ltd. No. 7059 glass substrate using the HR-CVD method with microwave power X = 60 W and under the conditions shown in Table 1 A.
0 people were deposited.

After that, under conditions B, 50 people were exposed to the i-type layer, and 50 people were again exposed to the n-type layer.
Repeat layer 100 times for 50 people to a thickness of approx.
Deposition of μm was performed. Thereafter, a permalloy mask was applied, AJZ vapor deposition was performed, and a coplanar type electrode was attached to prepare a sample (N-12). Similarly, the sample (N-
A sample (P-12) was prepared in the same manner as in 12). Furthermore, except for the microwave power X of 80W, the sample (N-
Samples (N-13) and (P-13) were prepared in the same manner as 12) and (P-12). Similarly, X is 100W
Samples (N-14) and (P-14) as
Samples (N-15) and (P-15) with 0W, samples (N-16) and (P-16) with X as 160W,
Samples (N-17) and (P-17) when X is 200W
was created.

The prepared samples (N-12) to (N-17) and (P-1
Table 4 shows the results of evaluating the electrical conductivity σd of the samples using 2) to (P-17). From Table 4, the electrical conductivity σd decreases as the microwave power increases, that is, as the hydrogen content increases, both in the case of a laminated thin film semiconductor using an n-type layer and in the case of a laminated thin film semiconductor using a p-type layer. I know what you're doing. In particular, as compared with Table 3, samples with hydrogen content exceeding 10 atomic ratio and microwave power of 120 W or more (N-
12) ~ (N-17) and (P-12) ~ (P-17)
It has been shown that b od is significantly reduced.

This decrease in Cd is considered to be due to the difference in the density of electrons in the case of a laminated thin film semiconductor using an n-type layer, and of holes in the case of a laminated thin film semiconductor using a p-type layer. pi
In an n-type photovoltaic element, the higher the electron density of the n-type layer and the electron density of the p-type layer, the more difficult it is for the n-type layer or the p-type layer to become a depletion layer, and the lower the drop in potential is, so the higher the open circuit voltage V is. C is obtained. Furthermore, since the electric field strength in the i-type layer between the p-type layer and the n-type layer increases, the fill factor (F, F,) also increases.

From the results of (1) and (2) above, in a pin-type photovoltaic device using a silicon thin film semiconductor, the p-type layer and/or the n-type layer is thinner with a -layer thickness of 100 Å or less.
A structure in which a type layer and an i-type layer are laminated two or more times (hereinafter referred to as a p-type laminated thin film semiconductor), and/or a layer with a thickness of 100 Å.
Conversion efficiency is achieved by creating a structure in which the following thinner n-type layers and i-type layers are laminated two or more times (hereinafter referred to as n-type laminated thin film semiconductor), and by keeping the hydrogen atom content in the film to less than 10 atomic ratio. A significant improvement was seen.

Further, when a photovoltaic element is used as an optical sensor, it is required that the saturation current as a diode is small as described above. As is well known, high open circuit voltage ■. Generally, a photovoltaic device exhibiting a low saturation current has a small saturation current, but the photovoltaic device of the present invention has an open circuit voltage V. C is high;
That is, it was found that the saturation current was small and that it exhibited excellent characteristics as an optical sensor.

Note that the present invention is not limited to the pin type device as described above, but can be used for any thin film photovoltaic device such as a Schottky type device or a Cd5-CdTe heterojunction device. . In addition, as elements contained in the thin film semiconductor layer, quaternary elements such as Ge%C other than the main Si
A genus element may be included. These matters will be illustrated in Examples.

[Examples] Hereinafter, it will be specifically shown by Examples that the present invention actually exhibits excellent characteristics as a photovoltaic element or an optical sensor. In addition, the gist of the present invention also applies to photovoltaic elements other than pin type,
It will also be shown that the present invention is applicable to other thin film semiconductor devices having Si as a main constituent element.

(Example 1) Using the apparatus shown in FIG. 3, a photovoltaic device according to the present invention having the configuration shown in FIG. 1 and a photovoltaic device having the configuration shown in FIG. A device was fabricated. Also,
We also evaluated these photovoltaic elements as optical sensors. In the following, samples (PV-2) to (PV-4) are examples of the present invention, and samples (PV-1) and (Pv-5) to
(PV-7) is a comparative example. In addition, a monolayer sample (pv
-1) is omitted, and in samples (Pv-2) to (PV-4),
It has a similar laminated structure.

Hereinafter, the steps for manufacturing the present example and comparative example will be explained with reference to FIG.

A stainless steel substrate with a size of 50 mm x 50 mm was placed in a sputtering device (not shown), and the inside of the device was heated for 10 minutes.
After evacuation to -'Torr or less, about 1000 Ag electrodes were deposited on the substrate as a lower electrode.

Next, in FIG. 3, this substrate 33 is placed in a substrate holder 32.
The heater is adjusted so that the substrate temperature is 300° C., and the vacuum chamber 31 is evacuated to 1 O −5 Torr or less.

Ar from the outer tube 34 at 250SCCM and H2 at 20SC
CM is flowed, and then 27 SCCM of SiF4 is poured from the inner tube 35.
and 33CCM of pFs diluted to 1% with SiF4 (
In total, SiF4 is about 30SCCM, PFs is 0.03S
CCM), and the exhaust speed was adjusted so that the pressure was 0.5 Torr. Next, 2.45G from the microwave power source
A microwave of 160 W at Hz was applied to generate plasma and film formation was started. In this way, an n-type layer was deposited to a thickness of 150 layers. Note that the manufacturing conditions are the conditions in A of Table 1 where x=160W.

At this point, the microwave input was temporarily stopped, the flow of PF5 was stopped, and the SiF4 was adjusted to 30SCCM, and then the microwave power

This manufacturing condition corresponds to the condition where x=160W in B of Table 1.

Stop the microwave input again and reduce the S i F4 flow rate to 2.
Furthermore, as 7SCCM, 3SCCM of BF3 diluted to 8% with SiF4 (total Si F4 is about 30S
CCM%BF, is 0.03SCCM), the microwave power X is set to 160W, the discharge is restarted, and the p-type layer is
50 people deposited. This manufacturing condition is C in Table 1, x=16
This corresponds to the condition of 0W.

After completing the formation of the three layers, n-type layer, i-type layer, and p-type layer, the sample was taken out from the apparatus, set in a vacuum evaporation apparatus (not shown), and evacuated to 10-' Torr or less. Sn
metal pieces were placed in a crucible at a weight ratio of 1:1, and heated by resistance heating in an oxygen atmosphere of approximately 1X10-3 Torr.
A TO thin film was deposited by about 700 people to form a transparent conductive layer. The substrate temperature at this time was 175°C. After cooling, take out the board,
A permalloy mask was placed on the transparent conductive layer, and the layer was placed in a vacuum evaporation device and evacuated to below 1X10-' Torr, and then Ag was deposited to a thickness of about 1.0 μm by resistance heating to form a comb-tooth-shaped current collecting electrode. This was designated as a sample (PV-1).

In this sample (pv-B), both the n-type thin film semiconductor layer and the p-type thin film semiconductor layer are single layers, and the structure is similar to that of the device shown in FIG. 2 described in the related art.
2 is a metal substrate, 22 is an n-type thin film semiconductor layer, 23 is a thin film semiconductor layer with no impurities mixed therein, 24 is a p-type thin film semiconductor layer, 25 is a transparent conductive layer, and 26 is a current collecting electrode.

In the samples (PV-2) to (PV-7) described below,
As shown in FIG. 1, an n-type thin film semiconductor layer and a p-type thin film semiconductor layer have a laminated structure.

In FIG. 1, 1 is a metal substrate, 2 is a thin film semiconductor layer mixed with P and made n-type, 3 is a thin film semiconductor layer that is not mixed with P, 4 is a thin film semiconductor layer that is not mixed with impurities, and 5 is a thin film semiconductor layer that is not mixed with P. 6 is a thin film semiconductor layer mixed with B to make it a p-type thin film semiconductor layer, 7 is a transparent conductive layer, and 8 is a current collecting electrode.

Condition A (x = aow) and Condition B (x =
60W), the n-type layer 2 and the i-type layer 3 were stacked three times by 50 people to form an n-type laminated thin film semiconductor, and then layered on top of it under condition B (x=160W) in Table 1. 5000 i
Deposit mold layer 4, and then apply condition C (x=60W) in Table 1.
and Condition B (X=60W), the p-type layer 5 and the i-type layer 6 are deposited three times by 50 people each to form a p-type laminated thin film semiconductor. Finally, the sample (similar to pv-B,
A transparent conductive layer of ITO thin film and a current collecting electrode were formed, and a sample (
PV-2).

The sample (PV
A sample (PV-3) was prepared in the same manner as in -2).

Follow the same procedure for x-100W and 120W.

Samples (PV-4) as 160W and 200W, respectively.
, (PV-5), (pv-a).

(PV-7) was produced.

The sample prepared in this way was irradiated with AM-1 light (100 mW/Cm2) from the ITO film side, and the short-circuit photocurrent I SC
+Open circuit voltage V. C1 fill factor, F.

and the conversion efficiency η were measured. The results of the measurements are shown in Table 5.

In Table 5, the sample (pv-B does not have a laminated structure of an n-type thin film semiconductor layer and a p-type thin film semiconductor layer, and I, c,
V. . , F, F, and η were the lowest values. On the other hand, samples (PV-2) to (PV-7) all have a laminated structure, but when compared with Table 3, samples (PV-5) to (PV-7) have a laminated thin film semiconductor structure. The hydrogen atom content exceeds 10%, which is outside the scope of the present invention. Therefore, these samples (PV-5) to (P
V-7), although the ISC is larger, the VO
C, F, and F are still low, and η cannot be said to be sufficiently high.

In contrast to the above comparative example, a sample (P
In V-2) to (PV-4), the hydrogen content in the laminated thin film semiconductor is less than 10 atomic ratio, and these are ■. 6.F.
-F also increased, and sufficiently good characteristics were obtained, which clearly demonstrates the effects of the present invention.

Next, the same sample (PV-1) ~ (PV-7) -5
Dark current with a reverse bias of V applied, 1 on the sample surface
00f1. Photocurrent when exposed to ux light and S/Nt
H (photocurrent/dark current) is shown in Table 6. As shown in Table 6, sample (pv-t) and sample (PV-5) ~ (P
Comparative example V-7) has a small S/N ratio and cannot be said to be practical. On the other hand, in the samples (PV-2) to (PV-4) with a hydrogen content of 10% or less, which are examples of the present invention, the S/N ratio was obtained at a value of 4 digits or more, and the The dynamic range is sufficient for practical use as a sensor. In other words, it is shown that the embodiment of the present invention is sufficiently effective as an optical sensor.

(Example 2) As an example of a photovoltaic element in which group 4 elements such as Ge and C are included in addition to the main Si as elements contained in the thin film semiconductor layer, a pin made of a p-type SiC laminated thin film semiconductor is used. An example of a type laminated thin film semiconductor device is shown.

Using the apparatus shown in FIG. 3, a p-type SiC thin film semiconductor was deposited on the same metal substrate as in Example 1 under the conditions p in Table 7, and a p-type SiC thin film semiconductor was deposited under the conditions E in Table 7. By depositing a SiC thin film semiconductor that does not contain any intervening impurities, it is more than 2f! A p-type laminated thin film semiconductor is produced by repeating the deposition of
Other conditions were the same as in Example 1, and samples (PV-8) and (PV-9) of thin film photovoltaic elements having the laminated structure shown in FIG. 1 were prepared.
was created.

Here, the sample (PV-a) is a comparative example, and the sample (PV-a) is a comparative example.
-9) is an example of the present invention. That is, the sample (PV
-8), the hydrogen content in the p-type laminated thin film semiconductor is 10 atomic ratio or more, and in the sample (PV-9), the hydrogen content in the p-type laminated thin film semiconductor is 10 atomic ratio or less. Hydrogen content was controlled by microwave power as described above.

Table 8 shows the results of measuring the characteristics of these samples as solar cells and optical sensors. The S/N ratio in Table 8 is 1 when applying a reverse bias voltage of -5V.
This is the ratio of photocurrent to dark current (photocurrent/dark current) when irradiated with light of 00 lux.

As shown in Table 8, the sample of the example of the present invention (PV-9
) compared to the comparative sample (pv-a), I! iC
1" 0C1F -F, + n + and S/N ratio are both improved, especially in the S/N ratio, the sample (P
V-9) is the sample (PV-8) (7310 times or more value). That is, the sample of the example of the present invention (PV-9
) has extremely good solar cell characteristics and optical sensor characteristics, and the effects of the present invention are clear. Also, for example, like the device using the p-type SiC laminated thin film semiconductor mentioned above,
It can be seen that even when the present invention is applied to a photovoltaic element in which a group 4 element such as Ge or C other than the main Si is contained in the thin film semiconductor layer, the same effect is exhibited.

(Example 3) As an example of a photovoltaic device other than a pin type photovoltaic device of the present invention, an example of a Schottky type photovoltaic device will be described.

Using the apparatus shown in FIG. 3, a Schottky thin film photovoltaic device sample (PV-10) and (
PV-11) was produced.

In addition, the sample (PV-10) is a comparative example, and the sample (PV-10) is a comparative example.
-tl) is an example of the present invention.

Here, 51 to 54 in FIG. 5 correspond to 1 to 4 in FIG. 1. That is, in FIG. 5, 51 is a metal substrate, 52 is a thin film semiconductor layer mixed with P to make it n-type, 53 is a thin film semiconductor layer not mixed with P, and 54 is a thin film semiconductor layer not mixed with impurities. It is. Further, 55 is an upper electrode,
56 is a current collecting electrode.

A conductive substrate such as stainless steel is used as the substrate 51, and a p-type or n-type thin film semiconductor layer 52 with a thickness of 100 Å or less is formed on the substrate 51 using the same manufacturing method as in Example 1 of the pin type element. and an i-type thin film semiconductor layer 53 having a thickness of 100 Å or less were laminated three times. Thereafter, an i-type semiconductor layer 54 is laminated, a semi-transparent gold film vacuum-deposited using a resistance heating method is formed as an upper chamber 8i55, and a thickness of 50 nm thick is formed.Finally, a final electrode 56 is formed.

Note that although the number of times of lamination in this example is three, the number of times of lamination may be at least two or more times. Further, the upper electrode 55 is made of, for example, Au or Pt.

Any light-transmissive conductive film may be used, such as a film made of Pd or the like to a thickness of 200 Å or less.

A sample of Schottky-type thin-film photovoltaic device with the above structure (
In PV-10) and (PV-11), the hydrogen content in the thin film semiconductor layer is controlled by microwave power. That is, in the sample of the comparative example (PV-10), the hydrogen content in the thin film semiconductor layer is 10 atomic ratio or more, and in the sample of the example of the present invention (PV-11), the hydrogen content in the thin film semiconductor layer is The atomic ratio is 10 or less.

Samples of these Schottky-type thin film photovoltaic devices (pv
Table 9 shows the characteristics of solar cells and optical sensors of -to) and (PV-11).

As shown in Table 9, the sample of the example of the present invention (PV-1
1) compared to the comparative example sample (PV-10), Isc,
”01: + Both F, F, , n, and S/N ratio have been improved, especially in S/N ratio,
V-11) has a value that is two orders of magnitude higher than that of the sample (PV-10). That is, the sample of the example of the present invention (
PV-11) had extremely good solar cell characteristics and optical sensor characteristics, and a significant improvement in conversion efficiency was observed. From this, the effects of the present invention are clear, and even when the present invention is applied to embodiments of photovoltaic elements other than pin type, such as the above-mentioned Schottky type photovoltaic element. , it can be seen that the effect remains unchanged.

(Example 4) As an example of a photovoltaic element produced by a method other than the HR-CVD method using the apparatus shown in Fig. 3, it was produced by the RF glow discharge method using SiH4 gas using the apparatus shown in Fig. 6. An example of a photovoltaic device manufactured by the present invention is shown below.

Using the apparatus shown in FIG. 6, samples of pin-type thin film photovoltaic elements (PV-12) and (PV-1) having the configuration shown in FIG.
3) was produced. Among these, sample (PV-12) is a comparative example, and sample (PV-13) is an example of the present invention.

In FIG. 6, reference numeral 61 denotes a vacuum chamber, which is evacuated in the direction of the arrow on the right side of the figure by a vacuum pump (not shown). Further, a grounded base holder 62 is provided in the vacuum N61, and a base 63 is fixed onto the base holder 62. The base 63 can be heated to a desired temperature by a heater provided within the base holder 62. Furthermore, a cathode electrode 64 is provided facing the base holder 62. The raw material gas introduced into the vacuum chamber 61 from the direction of the arrow on the left side of the figure by a gas introduction system (not shown) is transferred to the cathode electrode 64.
It is decomposed by the high frequency power of 13.56 MH2 applied to the substrate 63 and deposited as a thin film semiconductor on the substrate 63.

Using this apparatus, five types of thin film semiconductor layers were deposited under the manufacturing conditions shown in Table 10. That is, P in FIG.
An n-type thin film semiconductor layer 2 mixed with P is deposited under condition F, a thin film semiconductor layer 3 not mixed with P is deposited under condition G, a thin film semiconductor layer 4 not mixed with impurities is deposited under condition H,
A p-type thin film semiconductor layer 5 mixed with B is deposited under condition I,
A thin film semiconductor layer 6 without mixing was deposited under condition J.

The thickness of each layer is the same as in Example 1, and the metal substrate!
, the transparent conductive layer 7, and the current collecting electrode 8 are also the same as in Example 1.

A sample of the thin film photovoltaic device obtained as above (
In PV-12) and (PV-13), the hydrogen content in the thin film semiconductor layer is controlled by microwave power. That is, in the sample of the comparative example (PV-12), the hydrogen content in the thin film semiconductor layer is 10 atomic ratio or more, and in the sample of the example of the present invention (PV-13), the hydrogen content in the thin film semiconductor layer is The atomic ratio is 10 or less.

Table 11 shows the results of measuring the characteristics of samples (PV-12) and (PV-13)+7) as solar cells and optical sensors.

As shown in Table 11, the sample of the example of the present invention (PV-
13) has a higher Isc than the comparative sample (PV-12).
, Voc, F, F, , rl, and S/N ratio are both improved, and especially in the S/N ratio, the sample (
PV-13) has a value that is two orders of magnitude higher than the sample (PV-12) (7) value. That is, the sample (PV-13) of the example of the present invention has extremely good solar cell characteristics and optical sensor characteristics, and good characteristics as a solar cell and optical sensor can be obtained by controlling the hydrogen content. The effects of the present invention are clear. Further, even when the present invention is applied to a photovoltaic element produced by a method other than the HR-CVD method, for example, as in the case of the RF Douglow discharge method using SiH4 gas mentioned above, the effect remains unchanged. I can see that it will work.

Note that although the number of times of lamination in this example is three, the number of times of lamination may be at least two or more times. Further, the upper electrode 55 is made of, for example, Au or Pt.

Any light-transmissive conductive film may be used, such as a film made of Pd or the like to a thickness of 200 Å or less.

Although Examples 1 to 4 have been shown above, the number of laminations of the thin film semiconductor of the photovoltaic device according to the present invention may be any number of times as long as it is at least two times or more. The metal substrate may be any commonly used material, such as a stainless steel plate with a polished surface. Further, as the transparent conductive film, for example, In20s
, SnO2゜IT O, ZnO2, etc., and Au
Any light-transmissive conductive film may be used, such as a film formed of Pt, Pd, or the like to a thickness of 200 Å or less.

Further, as the current collecting electrode, any commonly used electrode such as Ag may be used. As shown in Example 2, the main element contained in the thin film semiconductor layer is S.
Group 4 elements such as Ge and C may be included in addition to t.

[Effects of the Invention] As described above in the detailed description of the invention, according to the thin film photovoltaic device of the present invention, the short circuit current (rsc) of the device
, open circuit voltage (■.c), and fill factor (F, F,), and furthermore, it became possible to reduce the dark current when applying a reverse bias voltage to the device. That is, it has a great effect on improving various properties of the photovoltaic element, such as the conversion efficiency as a solar cell, the S/N ratio as an optical sensor, and the dynamic range.

Table 1 Table 5 Table 6

[Brief explanation of drawings]

FIG. 1 is a sectional view of a pin type thin film photovoltaic device according to the present invention, and this figure also serves as a sectional view of a conventional pin type thin film photovoltaic device using a laminated thin film semiconductor. Second
The figure is a cross-sectional view of a conventional pin-type thin film optoelectronic device that does not use laminated thin film semiconductors in the p-type layer and n-type layer, and FIG. 3 is the HR-CVD method used to fabricate the devices of Examples 1 to 3 of the present invention. 4 is a diagram explaining an experiment using the TOF method, FIG. 5 is a cross-sectional view of a Schottky thin film photovoltaic device according to the present invention, and FIG. 6 is a diagram of the device of Example 4. FIG. 2 is a schematic diagram of a film forming apparatus using high-frequency power used for manufacturing. 1.21.51...Metal substrate, 2,22.52...
n-type thin film semiconductor layer, 3,53... thin film semiconductor layer not mixed with P, 4,23.54... thin film semiconductor layer not mixed with impurities, 5,24... n type thin film semiconductor Layer 6... Thin film semiconductor layer not mixed with B, 7.25
．． 42...Transparent conductive layer, 8,26.56...Collecting electrode, 31.61...Vacuum chamber, 32.62...Substrate holder, 33.63...Base, 34... Outer tube, 35・
... Inner tube, 36... Applicator, 41... Glass substrate, 43.47-"SiN layer, 44-n type or n-type thin film semiconductor layer, 45.46... 48
...AJ2 membrane, 49...Pulse power supply, 55...Upper electrode, 65...Cathode electrode. Figure 4 Figure 6

Claims (1)

[Claims] A thin film semiconductor with a film thickness of 100 Å or less made p-type or n-type by mixing an impurity element during deposition on one or both sides of the thin film semiconductor, and a film thickness obtained by mixing an impurity element at a concentration different from the above impurity during deposition. At least one type of thin film semiconductor of 100 Å or less, a thin film semiconductor of 100 Å or less with a thickness of 100 Å or less mixed with an impurity element different from the impurity element during deposition, or a thin film semiconductor of 100 Å or less with no impurity element mixed therein. In a photovoltaic device formed by repeatedly depositing a thin film semiconductor of A photovoltaic element characterized by a sub-atomic ratio.