Drawing inspiration from the remarkable adaptability of the human eye, researchers from the Institute of Metal Research (IMR) of the Chinese Academy of Sciences have developed a novel phototransistor with tunable sensitivity. This breakthrough provides an efficient solution for detecting low-contrast targets in complex visual environments, which is a critical challenge for advanced machine vision systems in applications such as precision guidance and smart surveillance.

The results were published in Light: Science & Applications on January 1.

Conventional photodetectors often struggle to generate a strong electrical response to faint differences in light intensity, causing subtle targets to be lost in background noise. In contrast, the human retina can dynamically adjust its sensitivity to focus on specific intensity ranges. Mimicking this "on-demand" adaptive mechanism in compact electronic devices has proven difficult.

To address this challenge, the researchers led by Profs. SUN Dongming, LIU Chi, and Academician CHENG Huiming, drew direct inspiration from biology. They ingeniously integrated a specially designed photosensitive structure into the gate of a molybdenum disulfide (MoS₂) transistor. This key component of this design is a heterojunction diode made of pristine MoS₂ and oxygen-plasma-treated MoS₂. Like the photoreceptive proteins in the human eye, the electrical conductivity of this diode changes dynamically with incident light intensity.

This change alters the internal voltage distribution within the transistor, enabling precise tuning of its sensitivity window by an external gate voltage.

Consequently, the device can be set to dramatically respond only to a pre-selected, narrow range of light intensities—where a low-contrast target's signature lies—while effectively ignoring brighter or dimmer background noise.

The experimental results are striking. Compared to traditional photodetectors, this bioinspired device achieves a sensitivity improvement of over 1,000-fold for detecting minute light variations and exhibits exceptional noise immunity.

When configured into an imaging array, the technology clearly outperforms conventional sensors. It can stably and clearly identify patterns with very weak contrast against their background. This paves the way for next-generation, compact machine vision systems that can see what current technology easily misses.

Bioinspired phototransistor with tunable sensitivity (Image by IMR)