N-i-p Inorganic Perovskite/Organic Tandem Solar Cells Approaching 26% via Bottom Contact Modulation

Wide bandgap (WBG) perovskites in monolithic perovskite/organic tandem solar cells (POTSCs) face challenges like unregulated crystallization, severe defect traps, poor energetic alignment, and undesirable phase transitions, primarily due to unfavorable bottom interfacial contact. These issues lead to significant energy loss and device degradation. In this study, we synthesized customizable acidic tin oxide quantum dots (SQDs) to modulate the bottom interface contact in CsPbI2Br perovskite solar cells (PSCs). This design balances physical, chemical, structural, and energetic properties, initiating defect passivation, optimizing energy band alignment, enhancing perovskite film growth, and mitigating instability. We also elucidated the instability mechanism caused by alkaline-based tin oxide bottom contact, emphasizing the impact of tin oxide solution's acid/base properties on PSC stability and performance. Consequently, the WBG CsPbI2Br device achieved a record power conversion efficiency (PCE) of 19.2% with a 1.44 V open-circuit voltage (VOC). Our monolithic POTSCs demonstrated a PCE of 25.9% (certified at 25.1%), with superior stability under various conditions.