Visual adaptation that can autonomously adjust the response to light stimuli is a basic function of artificial visual systems for intelligent bionic robots. To improve efficiency and reduce complexity, artificial visual systems with integrated visual adaptation functions based on a single device should be developed to replace traditional approaches that require complex circuitry and algorithms. Here, we have developed a single two-terminal opto-sensor based on multilayer γ-InSe flakes, which successfully emulated the visual adaptation behaviors with a new working mechanism combining the photo-pyroelectric and photo-thermoelectric effect. The device can operate in self-powered mode and exhibit good human-eye-like adaptation behaviors, which include broadband light-sensing image adaptation (from ultraviolet to near-infrared), near-complete photosensitivity recovery (99.6%), and synergetic visual adaptation, encouraging the advancement of intelligent opto-sensors and machine vision systems.

Two-dimensional transition metal dichalcogenides (TMDs) are emerging as a promising complement for traditional semiconductor materials in ultrathin optoelectronic device fields. Developing a better understanding of high-energy C-exciton dynamics is essential for efficiently extracting hot carriers and building high-performance TMD-based light-harnessing devices; however, insight into the C-exciton dynamics remains scarce. To further understand the C-exciton dynamics, here, we have unraveled the interrelation between C-exciton and band edge A-exciton dynamics in monolayer WS₂ by transient absorption spectroscopy. It is found that the band edge A-excitons could effectively generate high-energy C-excitons via the many-body process, and, in turn, the hot carriers relaxing from C-excitons to band edge states could compensate and slow the decay of the A-excitons. The comprehensive understanding of the interrelation between C-exciton and A-exciton dynamics in monolayer TMDs may trigger the potential applications for future TMD-based light-harvesting devices.