Solid-state selenization of printed Cu(In,Ga)S2 nanocrystal layer and its impact on solar cell performance

Abstract

Cu(In,Ga)S2nanopowder was printed on Mo-coated sodalime glass substrates and selenized from a Se-coated cover glass. The selenized Cu(In,Ga)(Se,S)2 film consisted of three layers with a different morphologies and micro-structures. Although the top layer showed large grains recrystallized from nanocrystals, the bottom layer was almost identical to the original precursor. The middle layer, as a thin boundary layer was found to be a mixture of carbon and Cu sulfoselenide. At a higher Se thickness (>1.2μm), a lower fill factor and short circuit current density were obtained, which might result from the accumulation of a Cu secondary phase. The solar cell, which consisted of Al2O3:ZnO/i-ZnO/CdS/Cu(In,Ga)(S,Se)/Mo/glass using the selenized absorber, showed the following properties: efficiency=8.28%, Jsc=26.14mA/cm2, Voc=0.483V, and fill factor=65.58% for AMG1.5 at 25°C.