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‐C₆₁‐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.