A sandwich-like electron transport layer to assist highly efficient planar perovskite solar cells.

Co-modification of an electron transport layer (ETL) with metal oxides and organic molecules can optimize the structure of the ETL and improve the performance of perovskite solar cells (PSCs). Here, a sandwich-structured ETL consisting of MgO/SnO2/EA was designed by co-modifying a SnO2 ETL with magnesium oxide (MgO) and ethanolamine (EA). The device with an ETL modified with MgO and EA has excellent performance in enhancing electron transport and blocking holes. It also inhibits the formation of deep defect states and improves the stability of the device. The introduction of MgO effectively improves the open-circuit voltage (VOC) of the device, while EA increases the short-circuit current density (JSC). The optimal efficiency of the PSC using the ETL co-modified with MgO and EA is 20.23%, which is much higher than that of the device with the unmodified SnO2 ETL (17.94%). The method described here provides an effective way to develop high performance ETLs co-modified with metal oxides and organic compounds for perovskite-based optoelectronic devices.