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

Phototransistors represent promising candidates for next-generation photodetectors due to their inherent signal amplification capabilities. In this study, we present a DPP-DTT/FA0.9Cs0.1PbI3 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 FA0.9Cs0.1PbI3 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 × 104 and 2.35 × 105, photoresponsivity values of 0.12 and 2.01 A/W, and photo detectivity values of 1.09 × 1012 and 1.71 × 1013 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.