Photovoltaic properties of ZnO/CdTe heterojunctions prepared by spray pyrolysis

An extended investigation has been made of the electrical and photovoltaic properties of heterojunctions prepared by spray-pyrolysis deposition of thin ZnO films on single-crystal p-type CdTe. The principal experimental variables were the substrate temperature and the postdeposition temperature for annealing in H2. Under actual sunlight the optimum cell showed an open-circuit voltage of 0.54 V, a short-circuit current of 19.5 mA/cm2, and a solar efficiency (referred to the active area) of 8.8%, the highest value obtained to date for an authentic heterojunction on CdTe. The nature of the forward transport mechanism has been investigated, and a tunneling model in which bulk and interface deep traps control the forward characteristics is shown to provide good correlation with the experimental data.