Recent advances of non-fullerene organic electron transport materials in perovskite solar cells

In perovskite solar cells (PerSCs), the electron transport layer (ETL) extracts and transports electrons from the perovskite light absorption layer (PAL) to the cathode, which plays an important role in improving the performance and long-term stability of the devices. Compared with fullerene derivatives, non-fullerene n-type organic semiconductors have some unique advantages, such as molecular structure diversity, ease of modification, adjustable frontier molecular orbitals, and good stability. Recently, non-fullerene electron transport materials (ETMs) have attracted more and more attention as efficient ETLs in PerSCs. A variety of non-fullerene ETMs have been reported. Herein, we summarized the latest developments of non-fullerene organic ETMs in PerSCs, including small molecular organic ETMs and polymer ETMs. Especially, the common effects of substituents and design strategies of molecular configuration on the properties of non-fullerene ETMs were systematically summarized. At the same time, the remaining challenges and promising future trends of PerSCs based on non-fullerene organic ETMs are discussed.