Highly-Efficient and Long-Term Stable Perovskite Solar Cells Enabled by a Cross-Linkable n-Doped Hybrid Cathode Interfacial Layer

Hybrid organic-inorganic halide perovskite solar cells (PeSCs) are currently at the forefront of emerging photovoltaic technologies due to their potential for providing cost-effective highly efficient solar energy conversion. The interfacial layers play an important role in determining the efficiency and stability of PeSCs. In this work, a solution-processed cross-linkable hybrid composite film composed of N,N-dimethyl-N-octadecyl(3-aminopropyl)trimethoxysilyl chloride silane (DMOAP)-doped [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) is demonstrated as an effective cathode interfacial layer for PeSCs. The hydrolyzable alkoxysilane groups on DMOAP enable moisture cross-linking through the formation of stable siloxane bonds, which is effective in ensuring uniform film coverage of PC₆₁BM on the perovskite layer and preventing the undesirable reaction between the mobile halide ions and Ag electrode. On the other hand, the quaternary ammonium cations on DMOAP can induce the formation of favorable interfacial dipoles, allowing the high work-function Ag layer to act as the cathode. Importantly, our results show that the chloride anions (Cl^-) on DMOAP can cause efficient n-doping of PC₆₁BM via anion-induced electron transfer, increasing the conductivity of PC₆₁BM film by more than 2 orders of magnitude. With these desired properties, the resulting devices show a remarkable power conversion efficiency (PCE) of 18.06%, which is superior to those of the devices with undoped PC₆₁BM film (PCE = 4.34%) and a state-of-the-art ZnO nanoparticles (NPs) interfacial layer (PCE = 10.40%). More encouragingly, combining this interfacial layer with an effective thin-film encapsulation layer, the resulting devices exhibit promising long-term ambient stability, with negligible (<5%) loss in PCE after more than 5000 h of aging.