Inorganic perovskite/organic tandem solar cells with 25.1% certified efficiency via bottom contact modulation

Wide-bandgap perovskites in monolithic perovskite/organic tandem solar cells face challenges such as unregulated crystallization, severe defect traps, poor energetic alignment and undesirable phase transitions, primarily due to unfavourable bottom interfacial contact. These issues lead to energy loss and device degradation. In this Article, we synthesize acidic magnesium-doped tin oxide quantum dots to modulate the bottom interface contact in wide-bandgap CsPbI₂Br perovskite solar cells. This design balances physical, chemical, structural and energetic properties, passivating defects, optimizing energy band alignment, enhancing perovskite film growth and mitigating instability. We also elucidate the instability mechanism caused by alkaline-based tin oxide bottom contact, emphasizing the impact of the tin oxide solution’s acid/base properties on the stability and performance of the device. Consequently, the wide-bandgap CsPbI₂Br solar cell achieves a power conversion efficiency of 19.2% with a 1.44 V open-circuit voltage. The perovskite/organic tandem solar cell demonstrates an efficiency of 25.9% (certified at 25.1%), with improved stability under various conditions.