Remarkable Cd-free Sb2Se3 solar cell yield achieved by interface band-alignment and growth orientation screening

Abstract

Sb₂Se₃ has attracted a lot of attention in recent years owing to its excellent photoelectrical properties. Eco-friendly TiO₂, with its wide band gap, is a promising candidate for the electron transporting layer (ETL) of Cd-free Sb₂Se₃ solar cells. However, the undesirable band alignment of the TiO₂/Sb₂Se₃ interface hinders its wide application. Herein, a TiCl₄-passivated TiO₂ ETL was introduced to solve this problem. The incorporation of Cl atoms leads to the enhanced (101) orientation of anatase TiO₂, by which the growth orientation of the Sb₂Se₃ film could be effectively tailored. The performance of the Sb₂Se₃ device with TiCl₄ treatment was dramatically enhanced by the improved band alignment at the TiO₂/Sb₂Se₃ interface, decreased interface defects, a pinhole-free ETL and enhanced crystal orientation. Finally, the synergetic improvement of the device parameters yielded a best device efficiency of 5.33% for a configuration of ITO/TiO₂/Sb₂Se₃/Au. In this configuration, the preferred band offset renders the highest open circuit voltage (V_oc) value (394 mV) in a Cd-free Sb₂Se₃ solar cell processed using vapor transport deposition (VTD). This work is expected to provide helpful guidance for future experimental efforts to improve Cd-free device performance and interface quality.