Performance of perovskite solar cells based on SnO2:DPEPO hybrid electron transport layer

The electron transport layer is an important functional layer of perovskite solar cells, and its surface and internal defects are critical parts of limiting the performance improvement of perovskite solar cells. The double electron transport layer (double ETL) strategy can effectively passivate inherent defects in the electron transport layer (such as SnO2) and improve electron extraction and transport between the functional layers, providing an effective way for developing efficient and stable PSCs. However, due to the existence of independent interfaces in the dual ETL, the cell mismatch in different ETL materials also leads to additional carrier defects, hindering the continuous advancement of the dual ETL strategy. This work proposes a strategy for introducing di[2-((oxo)diphenylphosphino)phenyl]ether (DPEPO) into SnO2 ETL to design a hybrid electron transport layer strategy. Using the hole-blocking effect of DPEPO, which has a higher HOMO energy level and good ability to transfer electrons, the intrinsic defects in SnO2 are successfully passivated, while significantly improving the crystalline quality of the SnO2 film surface. So, avoiding the direct contact between the perovskite photoactive layer and the conductive substrate can effectively improve the extraction and transport of electrons. Due to the preparation of high-quality electron transport layer, the crystallization regulation of perovskite thin film is further achieved, thereby improving the performance of perovskite solar cells. Finally, 21.53% of the power conversion rate is obtained, the open-circuit voltage (V-OC) reaches 1.220 V, the short-circuit current (J(SC)) is 23.19 mA/cm(2), and the fill factor (FF) is 76.11%. This efficiency is 1.39% higher than that of the control one. It is shown that the hybrid electron transport layer strategy can not only optimize the carrier transport dynamics efficiently and reduce the device performance affected by the defects in the functional layer significantly, but also regulate the perovskite crystallization, which has the prospect for preparing high-performance solar cells.