Low-Temperature Crystallized and Flexible 1D/3D Perovskite Heterostructure with Robust Flexibility and High EQE-Bandwidth Product

All-inorganic perovskite cesium lead triiodide (CsPbI₃) has attracted much attention among the perovskite family due to its excellent optoelectronic properties and chemical stability. However, the high-temperature crystallization process makes CsPbI₃ less compatible with commercially flexible substrates, limiting its application into flexible optoelectronics. Here, a cation of 1-(3-aminopropyl)-2pyrrolidinone (APP) is reported that can form 1D (APP)PbI₃ perovskite as templates, and significantly reduce the CsPbI₃ black-phase transition energy with a low annealing temperature of 75 °C, which further enables a flexible (APP)PbI₃/γ-CsPbI₃ (1D/3D) heterostructure photodetector on ITO/PET substrate. A high external quantum efficiency (EQE) greater than 2377% is observed along the orientated 1D/3D heterostructure. The high gain and low noise result in a high specific detectivity (D*) over 10¹² Jones under −0.6 V low bias. The optimized device structure brings a high EQE × bandwidth product of 119 kHz under a low driving bias. Due to the high toughness of orientated APP⁺ ions and the face-connected PbI₃]⁻ chains structure as a strong energy absorber, the flexible photodetector also shows excellent phase stability and impressive flexibility, remaining >90% initial responsivity after over 20 000 times bending with potential flexible imaging application in harsh environments.