Chlorine doping of Cu2O

Cu2O is a semiconductor suitable for photovoltaic applications. However, the highest efficiency obtained for a solar cell based on Cu2O is, to date, one order of magnitude lower than its theoretical limit. This could be due to the difficulties in the doping processes. In this paper we investigate the effects of chlorine doping on Cu2O. The doped material has a conductivity about one order of magnitude greater than the undoped material. The measurements of the carrier concentration as a function of temperature suggest that chlorine acts both as a donor, substituting the oxygen, and as an acceptor, sitting in an interstitial position. Moreover the p-type persistent photo-conductivity (PPC), shown by undoped samples after illumination, is very weak in the doped samples and it has a much longer decay time. Finally the effect of chlorine doping on the minority carrier lifetime is investigated by measurements of external quantum efficiency on Schottky junctions and the possible role of excitons is also discussed.