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

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 & DEG;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.