A systematic study on the deposition of μm thick CuInS2 spray ILGAR layers

The Spray Ion Layer Gas Reaction (ILGAR) is a new non-vacuum process, well suited for roll-to-roll production. In the first step of the process a metal salt solution is sprayed onto a heated substrate. The resulting solid layer is converted to the metal sulfide by H2S. Both steps are repeated until the desired thickness is achieved. Recently In2S3 buffer layers for highly efficient Cu(In,Ga)(S,Se)2 solar cells have been deposited by this method. Now we have significantly extended the process and enabled the deposition of copper containing compounds, such as CuInS2. By aerosol preheating, temperature optimization and the use of appropriate precursor-salts, the deposition rate has been increased from 3nm/cycle up to 35 nm/cycle in order to achieve μm thick films needed for solar cells. However, in addition to CuInS2, In2O3 was also detected, which was strongly reduced by H2S-postanealing. Nevertheless, XPS-, ERDA-, SEM- and EDX-measurements still revealed some structural and chemical inhomogeneities. Thus several approaches like a reducing atmosphere were tested to further improve the layer quality. Working solar cells have been produced with these CuInS2 absorber layers. Their optimization with respect to photovoltaic performance is in progress