8-Hydroquinolatolithium as a Highly Effective Solution-Processable Cathode Interfacial Material in Inverted Perovskite Solar Cells with an Efficiency Over 19%

The solution-processed 8-hydroquinolatolithium (Liq) has first been demonstrated as a highly effective cathode interfacial layer (CIL) in inverted perovskite solar cells (PSCs). Compared with the control device without a CIL, the Liq-based device possesses a faster charge transport rate, a lower surface work function of Ag electrode, a larger built-in potential, and a higher charge recombination resistance, probably due to the formed interface dipole between [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) and Ag induced by Liq, which eventually results in a great improvement of device performance. After optimization, the Liq-based PSC has achieved a power conversion efficiency higher than 19%. These results will assuredly expand the present limited range of available solution-processable cathode interfacial materials for low-cost high-performance PSCs.