Efficient photovoltaic devices based on p-ZnSe/n-CdS core-shell heterojunctions with high open-circuit voltage

For solar cells, high open circuit voltage is necessary for their high output voltage. Usually, two methods are used to increase the open circuit voltage: using suitable and matched large band-gap materials and reduction of saturation current. Herein, large band-gap p-type ZnSe nanowires and n-type CdS films are used to construct core-shell p-n heterojunctions with high open circuit voltage. Furthermore, a 4 nm Si3N4 layer is inserted between the ZnSe core and the CdS shell in order to passivate the interface defects and to reduce recombination and the saturation current. Additionally, a fast annealing process is employed to reduce the series resistance for improved performance. For a typical device, an optimum high open circuit voltage of similar to 1.3 V and an energy conversion efficiency of similar to 5.27% were achieved for its photovoltaic operation. Moreover, tens of devices were fabricated to demonstrate their stable and consistent performance.