Threo‐Chiral Cation Additive Enables Ordered Lattice Adsorption and Enhanced Operational Stability of Perovskite Photovoltaics

ABSTRACT Chiral molecular engineering is an effective strategy to modulate crystallization and mitigate nonradiative defects in perovskite solar cells (PSCs). However, unconstrained bond rotation often leads to spatial mismatch between chiral molecules and the perovskite lattice, hindering effective defect coordination. Herein, we introduce threo‐chiral cation additive of (2 S ,3 R )‐2‐amino‐3‐hydroxybutanamide hydrochloride (ThrA) to achieve precise perovskite lattice regulation. Benefiting from methyl‑induced steric hindrance originating from its dual chiral‑center threo‑configuration, ThrA acquires a conformationally locked rigid stereostructure and further facilitates thermodynamically‑favored parallel‑to‑lattice multi‑site synergistic adsorption via hydrogen bonding and Pb coordination. Such stereoselective “lock‐and‐key” interaction reduces lattice surface energy, guides preferential (100) crystal growth, and simultaneously suppresses lattice distortion and ion migration. Consequently, the ThrA‐modified inverted PSCs achieve a champion efficiency of 26.68% (certified 26.31%), while 65 cm 2 large‐area module delivers a promising PCE of 22.78% (certified 22.12%), representing one of the outstanding certification efficiencies for perovskite modules of comparable size. Unencapsulated devices retain 90% of their initial efficiency after 1000 h thermal aging (ISOS‐D‐2) and maintain 92% performance after 2000 h continuous maximum power point tracking (ISOS‐L‐2). This work demonstrates that the stereostructure of additive is decisive for precise perovskite crystallization modulation, providing advanced stereochemical strategy toward high‐efficiency and ultra‐stable perovskite photovoltaics.