CdTe:In - Post-Growth Doping and Proposals for Photovoltaic Devices

PV devices having n- rather than p-type CdTe absorbers offer the potential advantages of lower contact barriers and higher doping levels. In this work we present the results of post-growth doping trials using indium metal and indium chloride. The chemical incorporation of indium was measured by quantitative SIMS and the surface contamination resulting from indium chloride doping was evaluated by XRD and XPS. Carrier lifetimes were estimated by TRPL and the surface Fermi levels were measured by XPS. Trial junction structures were fabricated based on CdS and CdTe:In. These gave weak junctions as expected, but chlorine treatment gave PCE' of up to 10.3%. Such structures are not expected to out-perform n-CdS/p-CdTe junctions and we therefore propose a number of other junction designs for future studies which we assess here with SCAPS models.