Multifunctional Self-Combustion Additives Strategy to Fabricate Highly Responsive Hybrid Perovskite Photodetectors

To resolve the inherent trade-off issue between responsivity and detectivity in FA_0.9Cs_0.1PbI₃ perovskite photodetectors, this paper proposes a novel strategy using multifunctional self-combustion additives (urea and ammonium nitrate). During the early stages of crystallization, urea allows for the formation of a strong Lewis complex-derived low-dimensional intermediate phase; this suppresses the formation of perovskite nuclei, while ammonium ions assist the preferred grain growth along the [110] direction. During the high-temperature annealing steps, a self-combusting exothermic reaction occurs between urea as a fuel and NH₄NO₃ as an oxidizer, through which a locally supplied heat facilitates the removal of residual urea and byproducts. These multifunctional roles of self-combustible additives facilitate the production of high-quality, enlarged grain-structured perovskite films with improved optoelectronic properties, as confirmed by various analyses, including impedance spectroscopy and intensity-modulated photocurrent spectroscopy. The resulting FA_0.9Cs_0.1PbI₃-based photodiode-type photodetectors exhibit outstanding performance, such as a high responsivity (0.762 A W^-1) and specific detectivity (over 5.08 × 10¹³ Jones) at a very low external reverse bias (-0.5 V). Our findings clearly suggest that the multifunctional self-combustion additives strategy could help realize the full potential of FA_1-CsPbI₃ as a photodiode-type photodetector.