Fabrication of [001]‐Oriented FAPbI₃‐Based Photodetector With Excellent Air Stability Via Green Anti‐Solvent Additive Engineering

Abstract Formamidinium lead triiodide (FAPbI₃) exhibits excellent thermal and chemical stability, making it a suitable alternative for methylammonium lead triiodide (MAPbI₃) in high‐performance photodetectors. However, FAPbI₃ faces the challenge of transforming from the metastable photoactive black phase α‐FAPbI₃ to the photoinactive yellow phase δ‐FAPbI₃ at room temperature. This phase transition is accelerated in humid atmospheric conditions. To realize high‐performance FAPbI₃‐based photodetectors, it is crucial to form stable and highly crystalline phase‐pure α‐FAPbI₃ films. Herein, is fabricate highly stable and crystalline FAPbI₃ films and photodetectors through anti‐solvent additive engineering (AAE) using a green anti‐solvent (isopropanol, IPA) and an organic spacer (phenethylammonium iodide, PEAI). It is found that PEAI‐AAE treatment induced [001]‐preferred orientation growth in FAPbI₃ films, and passivated defects within the crystal. The photodetectors based on PEAI‐AAE‐treated FAPbI₃ film exhibits a fast response time of 485 µs/525 µs (rise time/fall time), high responsivity of 24.89 A W⁻¹, and excellent specific detectivity of 1.56 × 10¹³ Jones. Moreover, the PEAI‐AAE‐treated FAPbI₃ photodetector retained over 80% of its initial performance even after exposure to ambient air for over 720 h, demonstrating excellent long‐term stability. This study provides a green processing method that paves the way for future commercialization of perovskite‐based optoelectronic devices.