KR20100058751A - Method of fabricating absorption layer of solar cell - Google Patents

Abstract

PURPOSE: A manufacturing method of an absorbing layer of solar battery is provided to improve the property of the solar battery by preventing a thermal budget and improving a step coverage. CONSTITUTION: An absorbing layer(250) is formed on a substrate(240) within a vacuum chamber(200) by the sputtering process. The vacuum chamber keeps the vacuum with a pumping system(210). Sputtering targets(262, 264, 266, 268) use the selenium binary selenides or the compound in which the sulfur is added to the selenium binary selenides.

Description

Method of fabricating absorption layer of solar cell {Method of fabricating absorption layer of solar cell}

The present invention relates to a method of manufacturing an absorbing layer of a solar cell, and more particularly, to a method of manufacturing the absorbing layer of a solar cell having excellent properties when using a I-III-VI chalcogenide-based semiconductor as a material. .

Recently, as interest in alternative energy is increasing, research on low-cost and high-efficiency solar cells is being actively conducted. Current solar cells are mostly made of bulk type crystalline silicon substrates, but these solar cells have the advantages of high efficiency and reliability, but they are difficult to lower in cost, and the thickness of absorbing layer is generally about 200 ~ 300㎛. It is difficult and has the disadvantage that the process is intermittent. In contrast, thin film solar cells include amorphous silicon (a-Si), thin film polycrystalline silicon (thin film poly-Si), indium copper selenide gallium (CIGS), cadmium telluride compounds (CdTe), and organic materials. It is made of material, and the thickness of absorbing layer can be made as thin as 2 ~ 3㎛ thin, can be continuously mass produced using low cost substrates such as glass, metal or plastic, and it is a low energy consumption process. It has the advantage that it can be manufactured.

Among them, CIGS is one of the I-III-VI chalcogenide-based semiconductors represented by CuInSe ₂ and has a direct transition energy band gap (Eg) of about 1.04 eV. Such chalcogenide-based semiconductors include CIGSS (Cu (In _x Ga _1-x ) (Se _y S _1-y ) ₂ ) and CIS. The chalcogenide-based semiconductor has a high light absorption coefficient of about 1x10 ⁵ ㎝ ^-1 and shows high efficiency when used as a light absorption thin film.In order to meet the ideal bandgap of 1.40eV, part of Ga is replaced with In and Se is replaced with S. You may. For reference, the energy band gap of 1.6eV is CuGaSe _2, CuGaS ₂ is an energy band gap of 2.5eV. Such materials can be easily controlled by the bandgap only by controlling the composition of the constituent elements constituting the compound, and have high reliability since they have a long-term stability of more than 10 years.

1 is a cross-sectional view showing an example of a conventional thin film solar cell. Referring to FIG. 1, the thin film solar cell 10 includes a metal back electrode 110, an absorbing layer 120, a buffer layer 130, and a window on a sodaime glass substrate 100 having a thickness of 2 to 3 mm. The layer 140 and the upper electrode 150 are sequentially stacked. The metal back electrode 110 is formed by sputtering an Mo layer having a thickness of about 1 μm, and the absorption layer 120 forms a CIGS layer having a thickness of about 2 μm to 3 μm. As the buffer layer 130, a CdS layer having a thickness of about 50 nm formed by a chemical bath deposition (CBD) is used. As the window layer 130, an n-type ZnO: Al layer of about 50 nm formed by sputtering is used. In the thin film solar cell 10 having such a structure, the absorbing layer 120 is formed mainly by applying co-evaporation to a metal element or a binary compound, or co-sputtering a Cu-In-Ga alloy. After formation, the Se pellets are heated by halogen lamps to form selenide Cu-In-Ga alloys. However, when the absorption layer 120 is formed by the evaporation method, the thermal budget may be a problem because the temperature is higher than that of the sputtering process, and the evaporation method may be applied only to a specific material such as a metal. The difference is that sputtering is applicable to any material. In addition, sputtering is superior to the evaporation method in terms of step coverage, radioactive damage, and generation of pollutants. On the other hand, since the process of forming a Cu-In-Ga alloy by simultaneous sputtering and selenizing it is to form the absorbing layer 120 by two separate processes, the process is not only complicated but also when moving between equipments. There is a fear that the already formed Cu-In-Ga alloy is contaminated. In addition, when controlling the Se content through the Se pellet, it also has the disadvantage that it is difficult to precisely control the composition of Se in the CIGS layer.

Therefore, the problem to be solved by the present invention, in manufacturing the absorbing layer of the solar cell, can proceed in a single process without applying excessive heat to prevent the occurrence of contamination, it is possible to easily precisely control the composition of each component element It is to provide a method for producing an absorbing layer of a solar cell.

The present invention for solving the above technical problem, relates to a method for producing a compound solar cell by forming Cu (In, Ga, Al) (Se, S) ₂ on the substrate as an absorption layer, selenium binary compound or The absorption layer of Cu (In, Ga, Al) (Se, S) ₂ is formed by sputtering using the compound which sulfur was added to the selenium binary compound as a target.

According to the present invention, it is possible to provide a method of manufacturing an absorbing layer of a solar cell, which does not cause a problem in thermal budget, but also provides superior solar cell absorbing layer in terms of step coverage, radiation damage, and generation of pollutants. The characteristics of the manufactured solar cell can be improved, and the unit cost thereof can be lowered.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are only presented to understand the content of the present invention, and those skilled in the art will be capable of many modifications within the technical spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited to these examples.

2 is a view for explaining a method for manufacturing an absorbing layer of a solar cell according to the present invention. Referring to FIG. 2, a Cu (In, Ga, Al) (Se, S) ₂ sputtering process is performed on a substrate 240 in a vacuum chamber 200 in which a vacuum is maintained therein by a pumping system 210. Thereby forming an absorbing layer 250. In the sputtering process, a selenium binary compound or a compound in which sulfur is added to the selenium binary compound is used as the sputtering targets 262, 264, 266, and 268. More specifically, reference numeral 262 is a Cu _x Se _y or Cu _x (Se, S) _y target, reference 264 is an Al _x Se _y or Al _x (Se, S) _y target, and 266 is In. _x Se _y or In _x (Se, S) _y target, and reference numeral 268 is a Ga _x Se _y or Al _x (Se, S) _y target. In the manufacturing method of this embodiment, a separate power (not shown) is applied to each target to control the band gap of the absorbing layer by adjusting the composition of the component elements of the absorbing layer to be formed. Meanwhile, during the sputtering process, a rotation system 220 is provided to heat the substrate 240 by the heater 230 and rotate the substrate 240 horizontally to form an absorption layer 250 having a uniform thickness. The uniformity of the absorbing layer 250 is increased. When sputtering targets of selenide compounds serving as the material of the absorbing layer in the apparatus, and manufacturing the absorbing layer on the substrate, the process is simple because there is no separate selenization step, and the composition control of the element of the absorbing layer is easy. It is easy to achieve the bandgap adjustment through it.

1 is a cross-sectional view showing an example of a conventional thin film solar cell; And

2 is a view for explaining a method for manufacturing an absorbing layer of a solar cell according to the present invention.

Explanation of reference numerals for main parts of the drawings

100, 240: substrate

110: metal back electrode

120, 250: absorption layer

130: buffer layer

140: window layer

150: upper electrode

200: vacuum chamber

210: pumping system

220: rotating system

230: heater

262, 264, 266, 268: sputtering targets

Claims (6)

In a method of manufacturing a compound solar cell by forming Cu (In, Ga, Al) (Se, S) ₂ as an absorption layer on a substrate, sputtering using a selenium binary compound or a compound in which sulfur is added to the selenium binary compound as a target A method for producing a compound solar cell, comprising: forming an absorption layer of Cu (In, Ga, Al) (Se, S) ₂ . The method of claim 1, wherein the selenium binary compound is Cu _x Se _y , In _x Se _y , Ga _x Se _y, and Al _x Se _y . The compound of claim 1, wherein sulfur is added to the selenium binary compound, wherein Cu _x (Se, S) _y , In _x (Se, S) _y , Ga _x (Se, S) _y, and Al _x (Se, S) _y is a method for producing a compound solar cell. The method of claim 2 or 3, wherein the sputtering is performed by simultaneous sputtering to apply separate power to the selenium binary compound or the compound to which sulfur is added to the selenium binary compound to control the band gap of the absorbing layer. Method for producing a compound solar cell. The method for producing a compound solar cell according to claim 2 or 3, wherein the sputtering is performed during heating by a heater. The method of claim 1, further comprising rotating the substrate horizontally during the sputtering.

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