Gapless linear dispersion in Bi₂Se₃ nanoparticles for high-performance broadband photodetectors

Topological insulators have demonstrated novel optoelectronic properties owing to their gapless linear dispersion and robust surface states. In this study, we implemented high-performance broadband photodetectors based on mixed-dimensional heterostructure of the topological insulator Bi₂Se₃ nanoparticles (NPs) with the semiconductor WSe₂. Prominently, the Bi₂Se₃ NPs/WSe₂ structure exhibited photoresponsivity of 22.17 A/W in the visible (Vis) wavelengths, and 5 A/W in the near-infrared (NIR) wavelengths and a fast response time of 40 μs. In comparison with typical semiconducting PbS NPs/WSe₂ structure, we confirmed that the enhancement in the photoresponsivity, response time, and broadband photoresponse of the Bi₂Se₃ NPs/WSe₂ structure can be attributed to the gapless behavior in surface states of topological insulator materials. Numerical simulations also confirmed a dramatic increase in the interfacial electric field by two orders of magnitude, resulting from the surface states in topological insulator NPs. The observed experimental results and the proposed mechanism pave the way for the emergence of efficient optoelectronic devices based on topological insulator materials.