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‐crystalp‐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.