JPS5857914B2 - Manufacturing method of photoelectric conversion element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a photoelectric conversion element with improved power efficiency.

Conventionally, photoelectric conversion elements consisting of a heterojunction of n-type S n 02 and n-type S1 have been studied.

There are various reports regarding the open circuit voltage and fill factor of this photoelectric conversion element, and it has been difficult to obtain reproducibility even when the elements are manufactured under the same conditions.

The improvement of the manufacturing method that focuses on the open-circuit voltage is to intentionally create a thin 5in2 on the surface of the Si wafer and then apply SnO
This can be done by growing 2.

Unless the film thickness of this 5IO2 film is thicker than the film thickness that naturally occurs on the Si wafer surface by leaving it in air at a temperature of several tens of degrees Celsius or lower or by treating it with an oxidizing acid, there is a problem in terms of reproducibility.

However, the upper limit of the film thickness needs to be small enough to allow current to flow due to the tunnel effect.

The disadvantage of this stealing is that if you try to obtain the output as electricity,
The fill factor changes greatly depending on subtle changes in the thickness of the 5IO2 film, making it unsuitable for applications that extract electric power.

When growing Sn 02 on an 81 substrate from an oxidizing atmosphere containing at least Sn vapor or Sn compound vapor or Sn gaseous compound, the crystals are slightly degraded and have high resistivity at low growth temperatures. It was observed that a Sn02 film with many carrier recombination levels was obtained, and that a high growth temperature resulted in a 1', csn02 film with low resistance and good crystallinity.

Figure 1 shows n Summary 2) −/771, SnCl
2 is a Sn compound, H20 vapor is an oxidizing gas,
The growth temperature and resistivity ρ when 5bC15 is used as an n-type dopant, the open circuit voltage Voc under constant intensity tungsten lamp light as a photoelectric conversion element, and the terminal voltage ■ when outputting a short circuit current of 80 yen.

, 8 is shown. Note that the carrier gas flowing through the 5nC14 bubbler is approximately 0.51 layers/min, and the carrier gas flowing through the H20 bubbler is approximately 0.31 layers min.

The carrier gas flowing through the 5bC15 bubbler is approximately 0.31
The layer is min.

Terminal voltage■. , 8 is a number to indicate the fill factor, and the one that shows ideal diode characteristics is Voc-40m
It can increase up to a value of V.

Terminal voltage■.

, 8, the lower the power output.

The results of this experiment vary greatly even at the same temperature depending on the gas supply conditions and the history of the gas system, but the open circuit voltage Voc and the terminal voltage ■.

, 8 tends to increase as one becomes higher, so if the sample chamber is maintained and maintained strictly, the change in 320
'C to 360°C gives good results.

In this invention, compared to this condition, Voc
+ As a condition for obtaining large values for both Vo and s,
First, 10 or more low-temperature-grown S t 02 first layers, which are thought to have many minority carrier recombination levels, are grown on the Si, and then a layer with a lower resistivity than the first layer grown at a higher temperature is grown. Conditions are used to grow the second layer of SnO2.

In other words, from Figure 1, the growth conditions for the low resistance region are 340°C or higher, where there is little influence from changes in the concentration of raw materials in the gas due to the growth temperature dependence of resistivity ρ, and a region where there are many recombination levels of minority carriers. The growth conditions are an increase in resistivity ρ,
The temperature is set at 320° C. or lower using the increase in open circuit voltage Voc as an index.

According to the principles of this invention, a first S n 02 layer is formed on a Si single crystal below 320°C, a low resistance S n 02 layer is formed on a 340'CJl
Open circuit voltage Voc and terminal voltage ■ when growing the n02 region.

, 8 are shown in FIGS. 2 and 3. Figure 2 shows low resistance S
Open-circuit voltage Voc and open-circuit voltage of a 5n02/Si photoelectric conversion device manufactured by limiting the growth of the n02 region to 350°C or 380°C and changing the growth temperature of the first Sn02 layer to 320°C or lower ■.

, 8 shows the growth temperature dependence of the first S n 02 layer.

It is also superior in reproducibility and variation compared to the single growth temperature case shown in FIG.

Open circuit voltage V, oc and terminal voltage ■.

, 8 with the same temperature combination as shown in FIG. 1, the manufacturing conditions and the growth temperature range of the first S n 02 layer where a value equal to or higher than both can be obtained is 250'C to 320°
It is C.

Note that in this experiment, the first semiconductor S n
Although the thickness of layer 02 was varied from 10 to 1,000 layers, no significant change in properties was observed.

FIG. 3 shows the results when the growth temperature of the S n 02 layer of the first semiconductor was fixed at 300'C and the growth temperature of the low resistance S n 02 region was varied.

From 340 DEG C. to 420 DEG C., it gives better results than the manufacturing method shown in FIG.

Above 450° C., the electrical properties of the first semiconductor SnO2 layer appear to change during the growth of the low resistance SnO2 region.

Although it is necessary to change the temperature of the substrate between growth at a low temperature and growth at a high temperature, samples that continued to grow during this temperature change were even better in terms of reproducibility and characteristics.

In the above experiments, in the case of low resistance SnO2 growth, n-type impurities were mixed into the atmospheric gas, but this is not necessary if SnO2 with a low resistance value can be obtained.

In this experiment, the lead-out electrode on the S n 02 side was made of either A u +A g or Ni, and the lead-out electrode on the Si side was made of ultrasonic solder made of Ni1 low melting point metal alloy.

As described in detail above, according to the present invention, a photoelectric conversion element having a structure in which SnO2 is provided on Si and having a high power conversion efficiency can be obtained, and therefore it can greatly contribute to the solar cell industry in particular.

Furthermore, the manufacturing method of the present invention has the advantage that a desired photoelectric conversion element can be obtained with good reproducibility.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between growth temperature, resistivity, open circuit voltage, and terminal voltage in one embodiment of the manufacturing method of the present invention, and FIG. 2 is a diagram showing the relationship between growth temperature, open circuit voltage, and terminal voltage in another embodiment of the present invention. Similarly, FIG. 3 is a diagram showing the relationship between growth temperature, open circuit voltage, and terminal voltage in the low resistance SnO2 region. In the figure, Voc is the open circuit voltage, VO and S are the terminal voltages, and ρ is the resistivity.

Claims (1)

[Claims] I A Si thin film on a Si substrate or other substrate is coated with Sn vapor or a volatile Sn compound vapor or an oxidizing atmosphere containing a Sn gaseous compound in a temperature range of 320° C. or less. The present invention is characterized by comprising the step of growing 10 or more 02 films, and further growing SnO2 thereon in the above atmosphere or in an atmosphere in which an n-type dopant is added at a substrate temperature in the temperature range of 3408 C to 420 C. A method for manufacturing a photoelectric conversion element. 2. Start growing a Sn02 film on a Si thin film on a Si substrate or other substrate at a substrate temperature of 320°C or less in an oxidizing atmosphere containing Sn vapor, volatile Sn compound vapor, or Sn gaseous compound. A method for manufacturing a photoelectric conversion element, comprising the step of increasing the substrate temperature and growing an S n 02 film for a period of time until a predetermined film thickness is obtained in a temperature range of 340'C to 420°C. . 3. Start growing a SnO□ film on a Si thin film on a Si substrate or other substrate in an oxidizing atmosphere containing Sn vapor, volatile Sn compound vapor, or Sn gaseous compound at a substrate temperature of 320°C or less. After that, a step of mixing n-type impurities into the atmosphere, increasing the substrate temperature, and growing the S n 02 film for a period of time until a predetermined film thickness is obtained in a temperature range of 340° C. to 420° C. A method for manufacturing a photoelectric conversion element, comprising: