N ‐(2‐aminoethyl) Acetamide Additive Enables Phase‐Pure and Stable α‐FAPbI3 for Efficient Self‐Powered Photodetectors

Formamidinium-lead triiodide (FAPbI3 ) perovskite is considered as one of the most promising perovskite materials for high-performance photodetectors because of its narrow bandgap and superior thermal stability. Nevertheless, to realize efficient carrier transport and highly performing photodetectors, it imposes the requirement of fabricating α-FAPbI3 with pure phase, preferred crystal orientation, large grain size, and passivated interface, which still remains challenging. Here, a facile strategy based on additive engineering to obtain pure-phase FAPbI3 perovskite films by introducing N-(2-aminoethyl) acetamide into perovskite precursors is reported. The formation of chemical bond and hydrogen bond between N-(2-aminoethyl) acetamide and perovskite reduces the potential barrier in the phase-transition process from an intermediate yellow phase to a final black phase, passivates the defects of the film, and leads to a high-quality and phase-pure α-FAPbI3 perovskite. A self-powered photodetector based on the as-fabricated FAPbI3 film exhibits a maximum responsivity of 0.48 A W-1 at 700 nm with a peak external quantum efficiency of 95% at 440 nm. Moreover, the optimized device remains 83% of the initial performance after 576 h storage at ambient condition. This work provides a simple and feasible scheme for the preparation of high-quality phase-pure α-FAPbI3 perovskite and associated devices.