A perylene diimide-based electron transport layer enabling efficient inverted perovskite solar cells

A 3D type perylenediimide (PDI)-based molecule (TPE-PDI4) is successfully applied as an efficient electron transporting material in inverted perovskite solar cells (PSCs). TPE-PDI4 has been previously demonstrated as an excellent non-fullerene electron acceptor in high-performance bulk-heterojunction polymer solar cells. Considering its decent electron mobility and outstanding solution processability with favorable thin-film morphology, as well as compatible energy levels with perovskite materials, TPE-PDI4 serves as a promising candidate as the electron transport layer (ETL) material for perovskite solar cells. Herein, we report the fabrication of inverted perovskite solar cells using TPE-PDI4 as the electron transporting layer. A high PCE of 16.29% is obtained, which is higher than that obtained using a PCBM-based electron transporting layer under the same testing conditions. On the other hand, TPE-PDI4 also works well as an interfacial layer between perovskite and C60. A high efficiency of 18.78% is achieved in PSCs with TPE-PDI4 compared to a lower efficiency of 16.56% without this interlayer, indicating an enhanced charge transport/collection with the insertion of TPE-PDI4. Additionally, TPE-PDI4 shows a better water-resistibility than PCBM, which could more effectively protect the perovskite layer beneath. Therefore, devices with a TPE-PDI4-based ETL exhibit an enhanced stability. Our results demonstrate the great potential of TPE-PDI4 to replace expensive fullerene-based ETLs.