Improving the photovoltaic performance of solid-state ZnO/CdTe core–shell nanorod array solar cells using a thin CdS interfacial layer

Abstract

The properties of the electron donor–acceptor interface play a crucial role in the photovoltaic performance of the core–shell nanorod array solar cells (NRASCs). In this paper, all-inorganic solid-state ZnO/CdTe and ZnO/CdS/CdTe core–shell NRASCs have been fabricated by a simple low temperature and low cost solution-based process. We investigate the influence of the CdS interfacial layer with different thicknesses on the performance of the solar cells. It is found that inserting such an interfacial layer can significantly improve the short-circuit current density and the open-circuit voltage of the device. The overall power conversion efficiency of the ZnO/CdS/CdTe core–shell NRASC with a 4 nm thick CdS interfacial layer can reach 0.72% under AM 1.5G illumination (100 mW cm⁻²), which is three times that of the ZnO/CdTe NRASC. The improvement in the performance is attributed to the designed graded energy band alignment of ZnO/CdS/CdTe and the passivation of surface defects of the ZnO nanorod by the CdS interfacial layer, which can result in the enhanced carrier separation and collection. The result clearly demonstrates that the performance of all-inorganic core–shell photovoltaic devices can be greatly improved with uncomplicated interface engineering.