CN103258896A - Manufacturing technology of soft CIGS thin film solar cell absorbing layer - Google Patents

Abstract

The invention discloses a preparation process for the absorbing layer of a flexible copper indium gallium selenium thin film solar cell, which utilizes a roll-to-roll production process and uses stainless steel with a thickness of 25-100 μm as a substrate. Firstly, the back electrode molybdenum layer is deposited on the substrate, and then the CIGS absorber layer is deposited by a three-step co-evaporation method. The first step is to co-evaporate In, Ga and Se elements at a substrate temperature of 300-400°C; the second step , when the substrate temperature is 550-580°C, co-evaporate Cu and Se elements until the film is rich in copper; the third step, when the substrate temperature is 550-580°C, co-evaporate In, Ga and Se elements, and finally get CIGS thin film satisfying the stoichiometric ratio. Through the roll-to-roll production process, the industrialized mass production of CIGS solar cells has been realized. Using this invention, a flexible CIGS solar cell with good conversion efficiency was prepared.

Description

Fabrication process of flexible CIGS thin film solar cell absorber layer

technical field

The invention relates to a preparation process of an absorbing layer of a flexible copper indium gallium selenium thin film solar cell, which belongs to the field of photoelectric elements, more precisely, belongs to the field of photovoltaic solar cells.

Background technique

Solar cells as a clean energy source have developed rapidly in recent years. Thin-film solar cells will become the development direction of solar cells in the future because of their advantages such as low cost, large-scale production, and easy integration. Among them, the copper indium gallium selenium thin film solar cell has the advantages of high light absorption coefficient, high conversion efficiency, adjustable band gap, high stability, strong radiation resistance, etc., and is considered to be the main material of the third generation solar cell (the first monocrystalline silicon, second-generation polycrystalline silicon, and amorphous silicon), and products have entered the solar cell market.

The highest conversion efficiency of a small sample CIGS thin-film solar cell reached 19.9% in March 2008, prepared by the US Renewable Energy Laboratory using a three-step evaporation method. Currently, the highest conversion efficiency of CIGS solar cells is 20.3% announced by German ZSW in August 2010, but its area is only 0.5cm ² . Due to the difficulty in controlling the element ratio of copper indium gallium selenide solar cells and the difficulty in achieving uniformity of the film, it is extremely difficult to prepare large-area CIGS thin film solar cells, the conversion efficiency is low, and the manufacturing equipment is expensive.

Contents of the invention

The invention relates to a preparation process of a flexible copper indium gallium selenium thin film solar battery absorption layer. The mass production of copper indium gallium selenium thin film solar cells can be realized by using the roll-to-roll preparation method. By adopting the preparation method, the stability of the large-area CIGS film preparation process and the uniformity of the film can be improved. Using the roll-to-roll method, combining rewinding and winding, and using the three-step co-evaporation method, the prepared film has high quality, good uniformity, and high battery yield, which is the best way for industrial mass production.

The invention relates to a preparation process of a flexible copper indium gallium selenium thin film solar battery absorption layer. Firstly, the isolation layer chromium and the bottom electrode layer molybdenum are sputtered by magnetron sputtering on the flexible stainless steel substrate. The absorbing layer CIGS was then evaporated using a three-step co-evaporation method using a roll-to-roll process.

Fabrication process of flexible copper indium gallium selenide thin film solar cell absorber layer. The three-step method includes the following steps:

First, at a substrate temperature of 300-400°C, co-evaporate In, Ga and Se elements to form a (In _1-x Ga _x ) ₂ Se ₃ pre-layer, and the element ratio during the preparation process is Se/(In+Ga) The flow ratio is greater than 3.

(In, Ga)+Se→(In _1-x Ga _x ) ₂ Se ₃

Secondly, when the substrate temperature is 550-580°C, co-evaporate Cu and Se elements, use a constant power to heat the substrate, and end this step when the substrate temperature drops rapidly during the preparation, and a copper-rich CIGS film will be formed .

(In _1-x Ga _x ) ₂ Se ₃ +Cu+Se→Cu(InGa)Se

When the composition ratio of Cu and Se reaches the amount of CIGS, continue to deposit Cu and Se. When the temperature is higher than 523°, CuxSe exists in the form of liquid phase, which has strong thermal radiation, so that the heat of the substrate Radiation is greater than absorption, causing the substrate temperature to drop rapidly, so the point of rapid substrate cooling can be taken as the end point of the second step.

Finally, keep the temperature at the bottom of the second step, evaporate the three elements of In, Ga, and Se on the slightly copper-rich film, form an In-rich film on the surface of the film, and finally obtain CuIn _1-x that meets the required stoichiometric ratio _{GaxSe2 film} .

Description of drawings

Fig. 1 is a schematic diagram of the preparation process of an absorber layer of a flexible copper indium gallium selenide thin film solar cell according to the present invention. Among them: substrate heater 1, baffle plate 2, vacuum pump 3, inner cover 4, equipment shell 5, stainless steel substrate belt 6.

Fig. 2 is a scanning electron microscope (SEM) image of a CIGS solar cell prepared on a stainless steel substrate.

Detailed ways

In order to further understand the aspect characteristics, usability and feasibility of industrial mass production of the present invention, the embodiments are enumerated hereby, and the detailed description is as follows in conjunction with the accompanying drawings:

Firstly, sputtering isolation layer chromium and bottom electrode layer molybdenum on a flexible stainless steel substrate with a thickness of 25-100 μm by magnetron sputtering. The absorbing layer CIGS was then evaporated using a three-step co-evaporation method using a roll-to-roll process. Step 1: At a substrate temperature of 300-400°C, co-evaporate In, Ga and Se elements to form a (In _1-x Ga _x ) ₂ Se ₃ pre-prepared layer. The ratio of elements during the preparation process is Se/(In+ Ga) The flow ratio is greater than 3. The second step: when the substrate temperature is 550-580°C, co-evaporate Cu and Se elements, use a constant power to heat the substrate, and end this step when the temperature of the substrate drops rapidly during the preparation, and a copper-rich layer will be formed. CIGS film. Step 3: Keep the sinking temperature of the second step, evaporate the three elements of In, Ga, and Se on the slightly copper-rich film, form an In-rich film on the surface of the film, and finally obtain a close to stoichiometric ratio CuIn _{0 7} Ga _{0 3} CIGS Thin Film of Se ₂

In the first step, the stainless steel coil 6 moves at a constant speed from a fixed direction with the speed controlled by precision electrodes.

In the second pass, the coil of stainless steel undergoes rewinding sputtering, moving in the opposite direction.

In the third step, the stainless steel coil rewinds again, and finally realizes three-step co-evaporation of a CIGS thin film that satisfies the stoichiometric ratio.

Claims (8)

1. the preparation technology of a flexible CIGS thin-film solar cell absorbed layer, it is characterized in that: utilizing the production technology of volume to volume, is substrate deposition back electrode molybdenum layer with the stainless steel, utilizes the method deposition CIGS absorbed layer of three-step approach coevaporation then.

2. preparation method according to claim 1, it is characterized in that: the substrate of flexible CIGS thin-film solar cell is the thick stainless steel bands of 25～100 μ m.

3. preparation method according to claim 1 is characterized in that: the preparation form adopts the plated film mode of volume to volume (Roll-To-Roll), and the technology of this winding type is to realize the optimal path of large area film, production in enormous quantities.

4. preparation method according to claim 3, it is characterized in that: it is wide that the thin film solar cell width of preparation can be 300～100mm, the long 500～1000m of winding.

5. preparation method according to claim 1, it is characterized in that: the initial pressure of vaporization chamber is 2 * 10 ^-4Pa.

6. preparation method according to claim 1 is characterized in that: three-step approach is adopted in the preparation of absorbed layer, specifically comprises following processing step:

(1) when 300～400 ℃ of underlayer temperatures, coevaporation In, Ga and Se element, evaporation time are 15～25 minutes.

(2) when 550～580 ℃ of underlayer temperatures, coevaporation Cu and Se element finish when the rich copper of film.

(3) when 550～580 ℃ of underlayer temperatures, coevaporation In, Ga and Se element finally are met the CIGS film of stoichiometric proportion.

7. preparation method according to claim 1 is characterized in that: the thickness of the CIGS absorbed layer of final preparation is 1.5～2.5 μ m.

8. preparation method according to claim 1, it is characterized in that: the hull cell stoichiometric proportion of preparation is near CuIn _1-xGa _xSe ₂

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