ZnO/CdTe and ZnO/CdS core-shell nanowire arrays for extremely thin absorber solar cells

Abstract

In this study we report on ZnO/CdTe core-shell nanostructures fabrication for extremely thin absorber (Eta)-solar cells. Successive ion layer adsorption and reaction (SILAR) and close space sublimation (CSS) methods were used to sensitize electrodeposited ZnO nanowires by CdS and CdTe. The close morphological investigation showed that CdTe thin layer deposited by CSS method did not uniformly cover the ZnO nanowires (NWs). On the tip of the NWs, nanoparticles with a 20 nm diameter were observed whereas some areas were not covered, which could affect the solar cell efficiency. ZnO/CdS nanowires arrays were prepared by SILAR technique and were compared to those of ZnO/CdTe. The obtained uniform layers (∼ 25 nm thick) on the entire ZnO NWs surface allowed us to consider SILAR method as a good alternative for deposition of conformal extremely thin films. The adsorption edge up to 800 nm for CdTe compared to 500 nm for CdS, foresees the ZnO/CdTe core/shell structure favourable to achieve good photovoltaic performances. Enhanced optical properties of the nanostuctured electrodes over the planar counterparts proved the effect of the increased surface area.