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 (VOC) 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 VOC and fill factor (FF) of the devices are enhanced without sacrificing the photocurrent density (JSC). With optimal post‐treatment conditions, the champion device delivers a VOC of 1.02 V and an FF of 0.70 with JSC 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. Post‐treating the mesoporous TiO2/ZrO2/carbon triple layer by alkali metal sulfonate compounds enables a significantly enhanced photovoltage for hole‐conductor‐free printable mesoscopic perovskite solar cells. The devices demonstrate high operational stability, retaining 91.7% of their initial efficiency after 1000 h continuous operation at the maximum power point under 1 sun illumination.