• Witte, W.; Abou-Ras, D.; Hariskos, D.: Improved growth of solution-deposited buffer layers on Cu(In,Ga)Se2. Physica Status Solidi - Rapid Research Letters 10 (2016), p. 300-304


CdS and Zn(O,S) grown by chemical bath deposition (CBD) are well established buffer materials for Cu(In,Ga)Se2 (CIGS) solar cells. As recently reported, a non-contiguous coverage of CBD buffers on CIGS grains with {112} surfaces can be detected, which was explained in terms of low surface ener­ gies of the {112} facets, leading to deteriorated wetting of the chemical solutionon the CIGS surface. In the present contri­ bution, we report on the effect of air armealing of CIGS thin films prior to the CBD of CdS and Zn(O,S) layers. In cantrast to the growth on the as-grown CIGS layers, these buffer layers grow densely on the annealed CIGS layer, even on grains with {112} surfaces. We explain the different growth behav­ ior by increased surface energies of CIGS grains due to the armealing step, i.e., due to oxidation of the CIGS surface. Reference solar cells were processed and completed by i-ZnO/ZnO: Allayers for CdS and by (Zn,Mg)O/ZnO: Al for Zn(O,S) buffers. For solar cells with both, CdS and Zn(O,S) buffers, air-annealed CIGS films with improved buffer cover­ age resulted in higher power-conversion efficiencies, as com­ pared with the devices cantairring as-grown CIGS layers.