Self-powered SnS_x/TiO₂ photodetectors (PDs) with dual-band binary response and the applications in imaging and...

In this work, we report the design and fabrication of self-powered binary response PDs based on II-type heterostructures consisting of SnS_x nanoflakes (NFs) and rutile TiO₂ nanorod arrays (NRs). The TiO₂ NRs effectively block light with wavelengths below 400 nm from reaching SnS_x. Under 385 nm light, the photoelectrons in TiO₂ recombine with holes in SnS_x at the interface due to the energy band bending, resulting in a positive photocurrent. Under 410 nm light, the photoelectrons in SnS_x and the photogenerated holes in TiO₂ accumulate at the interface, overcoming the interfacial potential barriers induced by the higher Fermi levels of SnS_x and inducing a negative photocurrent. Based on the bipolar response, the dual-band imaging capability without external filters and the light-encrypted OR, AND, and NOT logic gates using a single device are demonstrated. This work provides a blueprint for the development of multifunctional self-powered PDs that can simplify system architecture, reduce the energy consumption, and improve accuracy for applications, such as visual systems, light-controlled logic circuits, and encrypted optical communications.