Synergistic Passivation and Down‐Conversion by Imidazole‐Modified Graphene Quantum Dots for High Performance and UV‐Resistant Perovskite Solar Cells

Abstract Organic–inorganic hybrid perovskite solar cells (PVSCs) have achieved stunning progress during the past decade, which has inspired great potential for future commercialization. However, tin dioxide (SnO2) as a commonly used electron transport layer with varied defects and energy level mismatch with perovskite contributes to the energy loss and limitation of charge extraction. Herein, imidazole‐modified graphene quantum dots (IGQDs) are introduced as the interlayer, which plays a significant role in three aspects: 1) dually passivating the defects of SnO2 and buried interface of perovskite by first‐principles calculations; 2) accelerating the carrier extraction and transfer owing to ideal band alignment; and 3) improving light utilization through down‐conversion proved by light intensity measurement. Consequently, the devices based on IGQDs/SnO2 not only exhibit the champion power conversion efficiency (PCE) of 24.11%, but display a significantly enhanced ultraviolet (UV) stability retaining about 81% of their initial PCEs after continuous UV irradiation (365 nm, 20 mW cm−2) for 300 h. Moreover, the unencapsulated modified device remains 82% after storing for 1650 h in air (20–30 °C, RH 45–55%). This work furnishes a novel method for the combination of interfacial passivation and photon management, which holds out for the prospect of employment in other optoelectronic applications.