Crystal orientation engineering toward high-performance photodetectors and their multifunctional optoelectronic applications

Pulsed-laser deposition has been developed to prepare large-area In₂S₃ nanofilms and their photoelectric characteristics have been investigated. The In₂S₃ nanofilm grown under 500 ​°C is highly oriented along the (103) direction with exceptional crystallinity. The corresponding (103)-oriented In₂S₃ photodetectors exhibit broadband photoresponse from 370.6 ​nm to 1 064 ​nm. Under 635 ​nm illumination, the optimized responsivity, external quantum efficiency, and detectivity reach 19.8 A/W, 3 869%, and 2.59 ​× ​10¹² Jones, respectively. In addition, the device exhibits short rise/decay time of 3.9/3.0 ​ms. Of note, first-principles calculations have unveiled that the effective carrier mass along the (103) lattice plane is much smaller than those along the (100), (110) and (111) lattice planes, which thereby enables high-efficiency transport of photocarriers and thereby the excellent photosensitivity. Profited from the sizable bandgap, the In₂S₃ photodetectors also showcase strong robustness against elevated operating temperature. In the end, proof-of-concept imaging application beyond human vision and under high operating temperature as well as heart rate monitoring have been achieved by using the In₂S₃ device of the sensing component. This study introduces a novel crystal orientation engineering paradigm for the implementation of next-generation advanced optoelectronic systems.