Post‐Treatment of Mesoporous Scaffolds for Enhanced Photovoltage of Triple‐Mesoscopic Perovskite Solar Cells

Triple‐mesoscopic perovskite solar cells (PSCs) based on TiO₂/ZrO₂/carbon architecture have attracted much attention due to their excellent long‐term stability and screen‐printing technique‐based fabrication process. However, the relatively low open‐circuit voltage (V_OC) limits the further improvement of power conversion efficiency (PCE) for triple‐mesoscopic PSCs. Herein, 2‐phenyl‐5‐benzimidazole sulfonate‐Na to post‐treat the triple‐mesoscopic structured scaffold is introduced. The conduction band of the mesoporous TiO₂ layer (electron transport layer [ETL]) is significantly shifted up from −4.22 to −4.11 eV, which favors the electron transfer from the perovskite absorber to the ETL. At the same time, the recombination at the interface of ETL/perovskite is effectively suppressed. Correspondingly, the V_OC and fill factor (FF) of the devices are enhanced without sacrificing the photocurrent density (J_SC). With optimal post‐treatment conditions, the champion device delivers a V_OC of 1.02 V and an FF of 0.70 with J_SC of 23.06 mA cm⁻², showing an overall PCE of 16.51%. After 1000 h continuous operation at the maximum power point under AM1.5G 1 sun illumination, the devices can maintain 91.7% of the initial efficiency. This simple procedure and significant photovoltage enhancement render this method promising for fabricating efficient PSCs based on mesoporous charge transport layers.