Low-cost coenzyme Q10 as an efficient electron transport layer for inverted perovskite solar cells

Abstract

Most of the electron transport layers (ETLs) used in inverted perovskite solar cells (PSCs) are fullerene derivatives, which are relatively expensive due to the complex synthesis process. Here we report coenzyme Q10, composed of quinone as the acceptor group and an alkyl chain as the donor group, which can be used as a low cost ETL alternative in inverted PSCs. The energy level alignments, carrier transport and recombination dynamics were systematically studied in comparison with the benchmark PC₆₁BM. By optimizing the device structure and thickness of the ETL, the device with Q10 exhibits a comparable power conversion efficiency to the PC₆₁BM device under the standard irradiation conditions. The carrier transport and recombination processes were further evaluated through steady state and time-resolved photoluminescence spectroscopy, space-charge-limited current, and Mott–Schottky measurements. An accelerated carrier injection ability and a passivated interface defect density between the perovskite and Q10 ETL were observed. Charge density difference from DFT calculations also determined that the band alignment of Q10 promoted easier charge transport from the perovskite. Moreover, the long alkyl chain of the Q10 molecule endows it with excellent hydrophobic properties, which largely improves the water-resistance capability of the Q10 ETL. This work highlights the great potential of Q10 as a cheap alternative for the most popular PC₆₁BM ETL for inverted PSCs.