Visual adaptation is a vital function of human sights. It allows us to process visual information under drastic changes in light intensities, from dim starlight to bright sunlight. Recreating visual adaptation with electronic devices is vital for developing novel artificial perception systems.

Complementary metal-oxide-semiconductor (CMOS) circuits have exhibited great potential for in mimicking visual adaptation since the 1990s, but they face the challenge of bulky size of large-scale integrated systems with complicated logic design.

Recently, researchers from the Institute of Chemistry, Chinese Academy of Sciences (ICCAS) created an organic active adaptation transistor (OAAT) to overcome the limitation and enable active-adaptation upon varied light intensities.

They introduced two functionally complementary bulk-heterojunctions (BHJs) in the active and composite dielectric layers, which serve as the photoresponsive active layer and a floating gate, respectively. The two BHJs initiate a photovoltaic effect-induced photoexcitation, as well as dynamic charge trapping-dominated inhibition, which couple together to modulate carrier concentration in the conductive channel.

This device exhibits phototriggered active adaptation behaviors for light intensities ranging over six orders of magnitude (1 to 10⁶ cd m^-2), and negligible changes were observed in output current after 1,000 repeated tests. The extracted active adaptation index (AAI) shows high similarity to that of human beings.

“In the longer term, such active adaptation transistors could potentially generate output signals that allow them to interface with the nervous system and used to create biomimetic visual prosthetics.” says News & Views of Nature Electronics.

This work was published as a cover story in Nature Electronics on Jul. 22, entitled “An organic transistor with light intensity-dependent active photoadaptation” and featured as News & Views of Nature Electronics.

visual adaptation in bioreceptors and a bioinspired organic active adaptation transistor (Image by HE Zihan)

Contact:
Prof. DI Chongan
Institute of Chemistry, Chinese Academy of Sciences
Email: dicha@iccas.ac.cn