A new approach for broadband photosensing based on Ag2Se/Si heterojunction tuned by Pyro-phototronic effect

With its high carrier mobility and low effective mass characteristics, silver selenide (Ag2Se) emerges as an attractive candidate for use in optoelectronic devices. However, the relatively low responsivity, slow response speed, and need for a large external bias largely limit their practical applications. In this manuscript, a newly photodetector (PD) is fabricated based on the n-Ag2Se/p-Si heterojunction. It is observed that this PD exhibits a broadband response range of 405–1064 nm at zero bias, and the best responsivity (R) and detectivity (D) are obtained to be 3.04 mA/W and 1.67 × 1010 Jones at 1064 nm, respectively, demonstrating its great potential in high-performance self-powered near-infrared (NIR) PD. More importantly, the light-induced pyroelectric effect, which can be employed to modulate the photoelectric processes and improve the photoresponse, is found in the Ag2Se film due to the imperfect orthorhombic structure. When the Pyro-phototronic effect is introduced in the heterojunction, the R and D of the PD are significantly enhanced to 43.32 mA/W and 1.75 × 1011 Jones with an argument of 1425 % , respectively. An ultrafast response time of 64/62 μs is simultaneously achieved under the illumination of a 400 Hz-pulsed laser, the performances of which are much better than those of previously reported Ag2Se-based heterostructure PDs. Besides, the response range is broadened beyond the bandgap of the heterojunction to a near-infrared region of 1550 nm. This study provides a novel pyroelectric material-based self-powered broadband PD and also gives a great promise for designing high-performance infrared ultrafast PD based on the Pyro-phototronic effect.