Fused-ring electron acceptor as an efficient interfacial material for planar and flexible perovskite solar cells

Abstract

Perovskite solar cell (PSC) has attracted great attention due to its high power conversion efficiency (PCE), low cost and solution processability. The well-designed interface and the modification of electron transport layer (ETL) are critical to the PCE and long-term stability of PSCs. In this article, a fused-ring electron acceptor is employed as the interfacial material between TiO 2 and the perovskite in rigid and flexible PSCs. The modification improves the surface of TiO 2 , which decreases the defects of ETL surface. Moreover, the modified surface has lower hydrophilicity, and thus is beneficial to the growth of perovskite with large grain size and high quality. As a result, the interfacial charge transfer is promoted and the interfacial charge recombination can be suppressed. The highest PCE of 19.61% is achieved for the rigid PSCs after the introduction of ITIC, and the hysteresis effect is significantly reduced. Flexible PSC with ITIC obtains a PCE of 14.87%, and the device stability is greatly improved. This study provides an efficient candidate as the interfacial modifier for PSCs, which is compatible with low-temperature solution process and has a great practical potential for the commercialization of PSCs. • A fused-ring electron acceptor ITIC is employed as the interfacial material for rigid and flexible perovskite solar cells. • ITIC not only suppresses the surface defects of TiO 2 film but also promotes the growth of perovskite crystals. • ITIC improves the electron extraction and reduces the charge recombination which contributes to the performance of PSCs. • The highest power conversion efficiency of 19.61% is achieved for the rigid PSCs after the introduction of ITIC. • Flexible PSC with ITIC obtains a power conversion efficiency of 14.87%, and the device stability is greatly improved.