Performance-limiting formation kinetics in green water-processed perovskite solar cells

Abstract

Water is the most sustainable and environmentally friendly solvent in material synthesis. Perovskite prepared from a water solvent-based precursor (Pb(NO₃)₂/H₂O) has been confirmed to be highly preferred and promising. Unfortunately, the sluggish conversion of Pb(NO₃)₂ to perovskite results in morphological flaws and incomplete transformation, which severely limit its photovoltaic performance. In this study, halide-free aqueous nanofluids (NFs) are prepared to regulate the formation kinetics of a perovskite via a grain refinement strategy. The crystallization process is examined by in situ UV-Vis absorption/PL measurements. It is found that both the microstructure of PbI₂ and anion configurations play a key role in the formation kinetics. Consequently, PbCO₃ NFs with an inert carbonate anion (CO₃²⁻) are carefully selected to promote the reaction rate by ∼30%. Moreover, CO₃²⁻ effectively inhibits the formation of FA vacancy defects at the surface of a nearly pure FA-based perovskite. The device made from PbCO₃ NFs in a fully dry-air atmosphere achieves an average PCE of 23.64% and a stabilized PCE of 23.95%. The bare device without any protection shows outstanding stability under continuous light illumination.