Conduction Band Energy-Level Engineering for Improving Open-Circuit Voltage in Antimony Selenide Nanorod Array Solar Cells

Abstract

Antimony selenide (Sb2Se3) nanorod arrays along the [001] orientation are known to transfer photogenerated carriers rapidly due to the strongly anisotropic one-dimensional crystal structure. With advanced light-trapping structures, the Sb2Se3 nanorod array-based solar cells have excellent broad spectral response properties, and higher short-circuit current density than the conventional planar structured thin film solar cells. However, the interface engineering for the Sb2Se3 nanorod array-based solar cell is more crucial to increase the performance, because it is challenging to coat a compact buffer layer with perfect coverage to form a uniform heterojunction interface due to its large surface area and length–diameter ratio. In this work, an intermeshing In2S3 nanosheet-CdS composite as the buffer layer, compactly coating on the Sb2Se3 nanorod surface is constructed. The application of In2S3-CdS composite buffers build a gradient conduction band energy configuration in the Sb2Se3/buffer heterojunction interface, which reduces the interface recombination and enhances the transfer and collection of photogenerated electrons. The energy-level regulation minimizes the open-circuit voltage deficit at the interfaces of buffer/Sb2Se3 and buffer/ZnO layers in the Sb2Se3 solar cells. Consequently, the Sb2Se3 nanorod array solar cell based on In2S3-CdS composite buffers achieves an efficiency of as high as 9.19% with a VOC of 461 mV.