Multifunctional Organic‐Perovskite Bilayer Phototransistor for R/G/B/NIR Broadband Detection and Photo‐Memory

ABSTRACT Phototransistors represent promising candidates for next‐generation photodetectors due to their inherent signal amplification capabilities. In this study, we present a DPP‐DTT/FA 0.9 Cs 0.1 PbI 3 bilayer phototransistor that integrates R/G/B/Near‐infrared (NIR) photodetection alongside photo‐memory functionality within a single device. The DPP‐DTT layer serves as a stable charge transport channel and a NIR‐responsive semiconductor, whereas the FA 0.9 Cs 0.1 PbI 3 layer functions as a visible‐light‐absorbing photoactive layer. Through optimization of the perovskite precursor molarity, a concentration of 0.10 M was determined to be optimal for balancing interfacial light absorption and leakage current suppression. Under these conditions, the bilayer device exhibited photosensitivity values of 1.50 × 10 4 and 2.35 × 10 5 , photoresponsivity values of 0.12 and 2.01 A/W, and photo detectivity values of 1.09 × 10 12 and 1.71 × 10 13 Jones under 520 and 850 nm illumination, respectively, at an intensity of 5 mW cm −2 . The optimized device demonstrated distinct photoresponse to illumination wavelengths of R/G/B/NIR. Furthermore, the device exhibited pulse‐dependent photo‐memory characterized by a short‐term memory (STM) to long‐term memory (LTM) transition. This work establishes a compact bilayer approach for the integration of multispectral sensing and optical memory in highly integrated multifunctional photodetectors.