Dual‐Functional Formic Acid Directs α‐Phase Perovskite Microcrystals From Industrial Precursors for High‐Yield and High‐Efficiency (>25%) Solar Cells

The solution‐based fabrication of perovskite solar cells (PSCs) typically relies on high‐purity materials, the cost of which limits commercial scalability. Here, we report an efficient strategy for directly synthesizing FAPbI 3 ‐based perovskite microcrystals (MCs) from industrial‐grade precursors using formic acid (HCOOH) as a multifunctional additive and antisolvent in a synergistic process combining inverse temperature crystallization (ITC) and antisolvent‐assisted precipitation. In situ grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) analysis reveals that formate anions (HCOO − ) coordinate with Pb 2+ to regulate crystallization, passivate structural defects, and promote the direct formation of α‐FAPbI 3 . An optimal HCOOH concentration (40%–60% v/v) was identified, achieving a high microcrystalline yield of 92.83% and effectively suppressing the formation of δ‐FAPbI 3 . However, concentrations exceeding this range (>80% v/v) disrupt the precursor stoichiometry, leading to PbI 2 impurity segregation. Thin films fabricated using the optimized microcrystals exhibited improved morphological uniformity, enhanced crystallinity, reduced nonradiative recombination losses, and extended charge carrier lifetimes. As a result, inverted‐structure PSCs based on these MCs achieve a champion power conversion efficiency of 25.24% (0.07 cm 2 ). This work presents a cost‐effective and scalable route for producing high‐quality perovskite materials and provides mechanistic insights into the dual functionality of HCOOH, offering valuable guidance for the advancement of low‐cost, high‐performance perovskite photovoltaic technologies.