One Material, Two Roles: Tungsten Oxide for Bifunctional Charge Transport in Inverted Perovskite Solar Cells

In this work, we explore the potential of tungsten oxide (WO x ) as a bifunctional material in inverted perovskite solar cells (IPSCs), simultaneously serving as both hole and electron transport layers (HTL and ETL) within the same device. By integrating WO x as HTL and ETL, we demonstrate a simplified device architecture [ITO/WO x /PTAA/MAPbI 3 /WO x /Al] and compare it to a conventional control structure employing PTAA as HTL and PC 61 BM as ETL. The WO x ‐based device achieved a power conversion efficiency (PCE) of 16.3%. Our findings demonstrated the viability of WO x as a multifunctional material, offering a path toward streamlined fabrication and reduced material complexity in PSCs. Notably, the WO x ‐based devices displayed superior long‐term stability under continuous 1‐sun illumination, maintaining over 95% of their initial efficiency after 1000 h of operation, in stark contrast to the control devices, which degraded significantly within the first 100 h. This enhanced operational stability is attributed to the robust physical and chemical properties of WO x , which act to suppress interfacial degradation and ion migration. This study paves the way for future exploration of multifunctional oxide materials in the development of high‐performance perovskite photovoltaics.