Restrained light-soaking and reduced hysteresis in perovskite solar cells employing a helical perylene diimide interfacial layer

An n-type helical molecule perylene diimide (PDI2) has been explored as an efficient interfacial layer between TiO2 and perovskite for the preparation of perovskite solar cells. The extended pi-conjugation of PDI2 ensures a high electron conductivity for efficient charge transport, and the oxygen atoms of the carbonyl groups can chelate with uncoordinated Pb2+ to passivate the surface defects of perovskite crystals. It thereby suppresses interfacial recombination, enhances efficiency, and reduces hysteresis and the light-soaking instability. The power conversion efficiency (PCE) of our perovskite solar cells showed negligible dependence on the thickness of the PDI2 interlayer, and the champion device achieved a high PCE of 19.84% and the hysteresis value (Delta PCE) was reduced to 2.34% compared to 6.46% in the perovskite device without the presence of the PDI2 interlayer.