|SEMICONDUCTOR NON-TRADITIONAL ENERGY SOURCES<|
Thin film solar cells on the base of polycristalline layers
Cu(In, Ga)Se2, (CIGS) Cu(In, Ga)SeS (CIGSSe)
Thin film Cu(In, Ga)Se2 and Cu(In, Ga)SeS solar cells have major potential as a source of low cost, high efficency solar electricety. The mass production of solar panels on the base of these materials is developing in several countries (USA, Germany).
The left figure shows the construction of the CIGSSe based solar cell in schematic form. By virtue of the fact that CIGSSe is a direct semiconductor with a high absorption capability, layers as thin as just 2Ám only are required for absorption of light. The p-type CIGSSe absorber layers are deposited on Mo covered glass (back contact) in two steps. At the first step the metal precursors Cu, In and Ga are sputtered onto the Mo covered glass. In the second step the CIGSSe absorber is completed by selenising and sulfurising the precursors due to a diffusion process. The solar cells are finished by chemical bath deposition of a very thin CdS buffer layer and a sequence of an intrinsic ZnO and n-type ZnO:Al window layer by sputter deposition. The electrical series connection of the modules individual cells occurs during the deposition process through the structuring of the individual layers. The entire manufacturing process is illustrated in right figure.