WO_x@PEDOT Core–Shell Nanorods: Hybrid Hole-Transporting Materials for Efficient and Stable Perovskite Solar Cells

PEDOT-coated WOx nanorodes (NRs) were prepared for the first time by simply stirring WOx nanowires (NWs) with 3,4-ethylenedioxythiophene (EDOT) in aqueous solution. A series of spectroscopic characterizations indicate that the polymerization of EDOT occurrs not only on the surface but also along the [010] planes of WOx NW, resulting in the truncation of long WOx NW to produce WOx@PEDOT NRs with abundant oxygen vacancies. Furthermore, WOx@PEDOT NRs were used to prepare a hole transport layer (HTL) in planar p–i–n perovskite solar cells (PeSCs). The WOx@PEDOT-based devices yielded a comparable average power conversion efficiency (PCE) of 12.89% with improved open-circuit voltage (VOC) and fill factor (FF) but lower short-circuit current density (JSC), as compared to the devices with conventional PEDOT:PSS (12.88%). The observed device performance is mainly attributed to the better perovskite texture on the WOx@PEDOT HTL, improved energy alignment, and suppressed charge recombination at the WOx@PEDOT/perovskite interface as well as lower charge conductivity of the WOx@PEDOT HTL. In addition, the PeSCs based on WOx@PEDOT-doped PEDOT:PSS showed remarkably improved PCEs up to 14.73%, which may be ascrible to the combined merit of WOx@PEDOT NRs and PEDOT:PSS. More impressively, benefiting from the inherent neutral nature of WOx@PEDOT NRs, WOx@PEDOT-based devices exhibited obviously improved stability compared to that with PEDOT:PSS HTL. These results thus demonstrate a path toward the development of new hybrid nanostructures for efficient and stable PeSCs.