Negative Photoconductivity in Porous Boron Nitride Nanofibers: For High On/Off Ratio Thermally Assisted Conductivity Modulation Photodetectors

This study demonstrates a high-performance thermally assisted conductivity modulation photodetector based on porous boron nitride nanofibers (BNNFs) exhibiting a unique negative photoconductivity (NPC) effect. Mechanism studies show that the NPC effect originates from the changes in conductivity generated by H₂O adsorption/desorption. The large specific surface area, abundant microporous/mesoporous structures, and hydrophilic groups of the porous BNNFs can provide active sites for the adsorption of H₂O molecules, which makes the photodetector have high conductivity in the dark. Under illumination, the laser-induced desorption of surface-bound H₂O molecules leads to a decrease in the conductivity. Based on the above mechanism, the porous BNNF photodetector exhibits broadband photoresponse (405–808 nm) and high on/off ratio (5 orders of magnitude change under 85% RH), and it maintains stability under high-power tolerance (>1 W cm^–2) due to the excellent thermal/chemical stability of porous BNNFs. Furthermore, the broadband photoresponse of the porous BNNF photodetector has been successfully applied to “NOR” and “NAND” optoelectronic logic gates. This NPC effect based on H₂O molecule adsorption/desorption on porous BNNFs provides a new option for the development of nontraditional optoelectronic devices for advanced optical logic gates and high-power photodetection. This work uncovers the distinctive optoelectronic characteristics of porous BNNFs, demonstrating their enormous potential for applications in optoelectronic devices.