Efficiency enhanced rutile TiO2 nanowire solar cells based on an Sb2S3 absorber and a CuI hole conductor

Abstract

Despite the excellent photo-generated charge separation and transport properties of the 1D rutile TiO₂ nanowire (NW) array, insufficient light harvesting due to a low surface area is a key factor that limits the photovoltaic performance of TiO₂ NW-based solar cells. Herein, we apply the Sb₂S₃ semiconductor as a light absorber and sprayed p-CuI as a hole conductor for TiO₂ NW solar cells. The Sb₂S₃-sensitized device displays significantly improved light absorption compared to its corresponding dye-sensitized device, with a peak incident-photon-to-current conversion efficiency (IPCE) of 64%. Moreover, CuI film deposited by the spray technique enables improved pore filling and better electrical contact between the Sb₂S₃ absorber and CuI, as well as CuI crystals themselves, and facilitates hole transfer from Sb₂S₃ to CuI crystals and hole transportation in the CuI layer. As a result, the TiO₂ NW/Sb₂S₃/CuI-spray/Au device exhibits an overall power conversion efficiency of 1.18% under AM 1.5G simulated solar irradiation, which is about 2.88 times and 2.11 times higher than TiO₂ NW/N719/CuI-spray/Au and TiO₂ NW/Sb₂S₃/CuI-drop coating/Au devices, respectively. This study thus demonstrates the superiority of the Sb₂S₃ sensitizer for TiO₂ NW solar cells and the spray technique for the preparation of the p-CuI hole conductor.