Secure optical communication increasingly demands encryption strategies that go beyond software-based algorithms and penetrate the physical layer. Here, we demonstrate an ultraviolet-visible bipolar photodetector that enables hardware-software collaborative encrypted information transmission by introducing signal polarity as an intrinsic physical key. The device is constructed using a vertical back-to-back N-I-P-I-N architecture based on a perovskite/organic hybrid heterojunction, where a thin p-type interlayer reconstructs the built-in electric field distribution and enables wavelength-dependent polarity reversal. As a result, the photodetector exhibits balanced bipolar responsivity with peak values of -0.16 and +0.13 A W^-1 in the ultraviolet and visible regions, respectively, microsecond-level response time, and a high specific detectivity exceeding 10¹² Jones. By combining polarity-encoded optical signals with software-based principal component analysis and spatial permutation, a multi-key image transmission system is realized. Image reconstruction requires simultaneous access to both the material-defined polarity key and the algorithmic key. The image reconstructed after decryption at the receiving end has high fidelity (PSNR > 30 dB). This work demonstrates how rational device architecture design can elevate photodetectors from passive receivers to active security primitives, opening a new avenue for physical-layer encryption in high-speed and covert optical communication.

Photoelectrodes with a specific structure and composition have been proposed for improving the efficiency of solar water splitting. Here, a novel multijunction structure was fabricated, with Si nanowires as cores, ZnIn₂S₄ nanosheets as branches, and TiO₂ films as sandwiched layers. This junction exhibited a superior photoelectrochemical performance with a maximum photoconversion efficiency of 0.51%, which is 795 and 64 times higher than that of a bare Si wafer and nanowires, respectively. The large enhancement was attributed to the effective electron–hole separation and fast excited carrier transport within the multijunctions resulting from their favorable energy band alignments with water redox potentials, and to the enlarged contact area for facilitating the electron transfer at the multijunction/electrolyte interface.

Among the important optoelectronic devices, ultraviolet (UV) photodetectors show wide applications in fire monitoring, biological analysis, environmental sensors, space exploration, and UV irradiation detections. Research interest has focused on the utilization of one-dimensional (1D) metal oxide nanostructures to build advanced UV photodetectors through various processes. With large surface-to-volume ratio and well-controlled morphology and composition, 1D metal oxide nanostructures are regarded as promising candidates as components for building photodetectors with excellent sensitivity, superior quantum efficiency, and fast response speed. This article reviews the latest achievements with 1D metal oxide nanostructures reported over the past five years and their applications in UV light detection. It begins with an introduction of 1D metal oxide nanostructures, and the significance, key parameters and types of photodetectors. Then we present several kinds of widely-studied 1D nanostructures and their photodetection performance, focusing on binary oxides with wide-bandgap (such as ZnO, SnO₂, Ga₂O₃, Nb₂O₅, and WO₃) and ternary oxides (such as Zn₂SnO₄, Zn₂GeO₄, and In₂Ge₂O₇). Finally, the review concludes with our perspectives and outlook on future research directions in this field.