Light-switchable 1D CsPbI₃@SWCNTs van der Waals heterostructures for negative photodetection and photosynapse devices

The applications of one-dimensional (1D) halide perovskite heterostructures based on single-walled carbon nanotubes (SWCNTs) remain an unresolved challenge. Herein, 1D van der Waals heterostructures composed of CsPbI₃ (CPI) encapsulated within semiconducting SWCNTs (CPI@s-SWCNTs) are designed for negative photodetectors and photosynapse devices via modulable photocarrier engineering. A single CPI@SWCNT device demonstrates a notable n-doping effect and exhibits negative photoresponse. Theoretical simulations reveal that the electrons transferred from CPI to SWCNT amount to 0.73e/cell. Large-area CPI@s-SWCNTs film can be obtained through the separation using the ultraviolet (UV) photosensitive polymer poly[9-(1-octyl-9H-carbazol-9-yl)-nonyl] (PCz). Under visible light irradiation, the large-area film device exhibits remarkable negative photoresponse (−9.3 A/W) owing to the photoelectric effect of internally filled CPI. Under UV irradiation, the film device exhibits synaptic behavior of electrical writing and optical erasing due to the persistent photoconductivity effect of the surface polymer PCz. This work not only provides a general strategy for the separation and application of halide perovskite filled SWCNTs, but also paves the way for broader applications of 1D van der Waals heterostructures in multifunctional optoelectronic devices.