Lithium Fluoride Nanolayer Modification of Substrates Upgrading the Performance of Perovskite Solar Cells

This is the authors' abstract. We don't add key points for this paper.

Perovskite solar cells (PSCs) have become a research hotspot in the photovoltaic field, while the fluorine-doped tin oxide substrate/electron transport layer (FTO/ETL) interface is a blind spot in PSC research. Hence, a nanolayer of alkali metal fluoride (MF: LiF, NaF, KF) is inserted into the interlayer between FTO and SnO2 ETL. In the subsequent annealing, F– anions are firmly adsorbed on the surface of the FTO anode, while some M+ cations diffuse into the SnO2 and perovskite to form a like-diffuse electric double layer (L-DEDL) and a built-in dipole field at the FTO/ETL interface. The L-DEDL optimizes the energy level alignment and suppresses the reverse migration of ions. Compared to K and Na, Li has a smaller ionic radius and a smaller electronegativity difference with F element, thus Li is more prone to diffuse and produce more significant modulation effects. Therefore, the LiF-modified device achieved a power conversion efficiency (PCE) of 26.13% along with improved stability, while the pristine device had a PCE of only 23.07%.