Solution-processable electron transport layer for efficient hybrid perovskite solar cells beyond fullerenes

A solution-processable planar perylene diimide, N,N'-dipentyl-3,4,9,10-perylenedicarboximide (PDI), has been demonstrated as a suitable acceptor material to replace the conventional fullerene derivatives (e.g., PCBM) found in inverted perovskite solar cells (PSCs). The energy offset between the perovskite and PDI layers was optimized by varying the ratio of halides (iodide to bromide) to improve the exciton dissociation and carrier transport. The PDI acceptor material had higher electron mobility and smoother morphology on perovskite relative to those of PCBM, leading to enhancements in the short circuit current density, fill factor, and power conversion efficiency. The incorporation of PDI in the perovskite devices decreased recombination losses and improved the device stability. The performance of the best PSC containing PDI as the electron transport layer (11%) was higher than that of the best device featuring PCBM (10%).