D-A-D typed fused-ring perylene diimide: A cathode interface material for efficient inverted perovskite solar cells

The interfaces between the cathode and electron transport layer significantly influence the photovoltaic performance and stability of perovskite solar cells (PSCs). Herein, a novel D-A-D typed fused-ring perylene diimide (PDI)-based organic small molecule, called PDTI1, is designed and employed as a cathode interface layer (CIL) for inverted PSCs. The introduction of PDTI1 at the interface of C60 and Ag electrode could form ohmic contact and the electron transport is also improved in the PDTI1-based devices. Based on these merits, the PSC with PDTI1-CIL achieves an impressive power conversion efficiency (PCE) of 24.64%. Notably, the PCE values of PSCs with the PDTI1 show thickness insensitivity. Furthermore, the PSCs with PDTI1 also exhibit better stability compared to the control devices. This work demonstrates the superior performance of PDTI1 as CIL for inverted PSCs and provides an alternative CIL material for high-efficiency PSCs.