Trifunctional Kinetic Regulation Enables Low‐Defect Solution Grown Single Crystals for X‐Ray Detection

ABSTRACT All‐inorganic 0D material exhibits excellent stability and shows great potential in the field of X‐ray detection. However, their practical performance is limited by intrinsic point defects and solvent incorporation. Herein, we propose a universal trifunctional kinetic regulation strategy utilizing iodoacetic acid (IAA) as a multifunctional additive to dynamically regulate crystal growth. Through a synergistic mechanism, the carboxyl group (‐COOH) coordinates with undercoordinated Pb 2+ to suppress deep‐level traps, released iodide ions (I − ) compensate for potential iodine vacancies (V I ), while the bulky ‐CH 2 I group provides steric hindrance against solvent incorporation. This molecular engineering approach yields Cs 4 PbI 6 single crystals that exhibit a resistivity of 1.95 × 10 10 Ω cm, and a remarkably enhanced carrier mobility‐lifetime product (µτ) of 2.18 × 10 −4 cm 2 V −1 . X‐ray detectors based on these crystals achieve a high sensitivity of 897.4 µC Gy air cm −2 and a low detection limit of 29.81 nGy air s −1 under an electric field of 1000 V cm −1 for 80 keV X‐ray detection, alongside robust operational and environmental stability. This work provides a molecular‐level design strategy for high‐performance perovskite single‐crystal X‐ray detectors.