Scalable Fabrication of High-Performance Self-Powered a-MoSe2 Thin-Film-Based Photodetectors on a-SiO2/Si Substrates

Owing to its high stability, suitable absorption band gap, and fast response time, MoSe₂ has attracted the most attention in transition-metal dichalcogenides (TMDCs) for photodetector (PD) applications. In this study, based on centimeter-scale smooth amorphous MoSe₂ (a-MoSe₂) thin films with thicknesses varying from 6.5 to 62.5 nm on a-SiO₂/Si substrates prepared by polymer-assisted deposition, metal-semiconductor-metal-structured self-powered a-MoSe₂ PDs are designed and fabricated. Our data show that the PD based on 9.5 nm thick a-MoSe₂ thin film exhibits the highest values of photocurrent (I_ph, 4.60 μA), photo-to-dark current ratio (PDCR, 3067), photoresponsivity (R_λ, 0.94 mA/W), and detectivity (D*, 4.29 × 10¹⁰ Jones), as well as the lowest values of noise-equivalent power (NEP, 2.33 × 10^-11 W/Hz^1/2) and photoresponse rise/decay time (61/58 ms) under a 405 nm laser with 5 mW power at zero bias, which are better than or comparable with those of previously reported PDs based on crystalline MoSe₂ monolayers or other atomically thin 2D materials under bias voltage. The high-performance mechanism can be explained in terms of the energy band theory and volume modulation photoconductive gain model in a-MoSe₂ with a spontaneous built-in electric field. Our work provides a scalable low-cost way for the design and fabrication of high-performance self-powered TMDC PDs.