MXene‐Induced Surface Plasmon Resonance and Carrier Regulation Enabling Bipolar Photothermoelectric FAPbI 3 /InAs Detectors for Optical Security Applications

ABSTRACT The FAPbI 3 /InAs heterojunction suppresses the high room‐temperature dark current of InAs while preserving its intrinsic photothermoelectric advantage, providing a promising platform for broadband and position‐dependent bipolar photodetection. However, the pure‐phase perovskite suffers from poor charge transport and defect‐related losses. To address these issues, Ti 3 C 2 T x MXene is employed for interfacial engineering. On the one hand, MXene enhances carrier transport, passivates defects, and tunes the energy level alignment; on the other hand, it improves photothermal conversion efficiency through broadband absorption and surface plasmon resonance, which synergizes with the intrinsic photothermoelectric effect of the InAs substrate. These two effects together improve the self‐powered detection performance of the detector. The optimized self‐powered FAPbI 3 /InAs photothermoelectric detectors exhibit outstanding performance, achieving a specific detectivity of 7.01 × 10 10 Jones (positive response) and 5.38 × 10 10 Jones (negative response) at 1550 nm, along with stable broadband detection from 642 to 3500 nm. Furthermore, by exploiting the unique current‐insensitive bipolarity, practical applications have been demonstrated in security and intelligent scenarios. These include single‐device logic gates (“AND,” “OR,” “NOT,” and “XOR”), dual‐channel encrypted communication via wavelength‐modulated response cancellation, and artificial neural network (ANN)‐assisted gesture recognition, thereby proposing a new strategy for high‐efficiency secure communications and non‐contact sensing.