A nanogenerator, as a self-powered system, can operate without an external power supply for energy harvesting, signal processing, and active sensing. Here, near-infrared (NIR) photothermal triggered pyroelectric nanogenerators based on pn-junctions are demonstrated in a p-Si/n-ZnO nanowire (NW) heterostructure for self-powered NIR photosensing. The pyroelectric-polarization potential (pyro-potential) induced within wurtzite ZnO NWs couples with the built-in electric field of the pn-junction. At the moment of turning on or off the NIR illumination, external current flow is induced by the time-varying internal electric field of the pn-heterostructure, which enables a bias-free operation of the photodetectors (PDs). The NIR PD exhibits a high on/off photocurrent ratio up to 10 and a fast photoresponse component with a rise time of 15 μs and a fall time of 21 μs. This work provides an unconventional strategy to achieve active NIR sensing, which may find promising applications in biological imaging, optoelectronic communications, and optothermal detections.

Nonpolar a-axial GaN nanowire (NW) was first used to construct the MSM (metal-semiconductor-metal) symmetrical Schottky contact device for application as visible-blind ultraviolet (UV) detector. Without any surface or composition modifications, the fabricated device demonstrated a superior performance through a combination of its high sensitivity (up to 10(4) A W(-1)) and EQE value (up to 10(5)), as well as ultrafast (<26 ms) response speed, which indicates that a balance between the photocurrent gain and the response speed has been achieved. Based on its excellent photoresponse performance, an optical logic AND gate and OR gate have been demonstrated for performing photo-electronic coupled logic devices by further integrating the fabricated GaN NW detectors, which logically convert optical signals to electrical signals in real time. These results indicate the possibility of using a nonpolar a-axial GaN NW not only as a high performance UV detector, but also as a stable optical logic device, both in light-wave communications and for future memory storage.

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Interfacial engineering and heterostructures designing are two efficient routes to improve photoelectric characteristics of a photodetector. Herein, a Ti3C2 MXene/Si heterojunction photodetector with ultrahigh specific detectivity (2.03 × 1013 Jones) and remarkable responsivity (402 mA W−1) at zero external bias without decline as with increasing the light power is reported. This is achieved by chemically regrown interfacial SiOx layer and the control of Ti3C2 MXene thickness to suppress the dark noise current and improve the photoresponse. The photodetector demonstrates a high light on/off ratio of over 106, an outstanding peak external quantum efficiency (EQE) of 60.3%, while it maintains an ultralow dark current at 0 V bias. Moreover, the device holds high performance with EQE of over 55% even after encapsulated with silicone, trying to resolve the air stability issue of Ti3C2 MXene. Such a photodetector with high detectivity, high responsivity, and self‐powered capability is particularly applicable to detect weak light signal, which presents high potential for imaging, communication and sensing applications.