Ag/AgCl‐Like Photogating of a COF‐on‐MOF Heterojunction in Organic Photoelectrochemical Transistor

Abstract The pursuit of high on‐to‐off ratio (I_On/I_Off), as one of the important performances for organic electrochemical transistor (OECT) has been ongoing, but to date, limited solutions are available. The interaction between light and matter has been demonstrated as a rich source for advanced electronic applications. However, its potential in I_On/I_Off modulation has not been fully explored. Herein, the challenge is addressed through the unique light‐material interplay, which is represented by organic photoelectrochemical transistor (OPECT) gated by photosensitive COF‐LZU1 on mixed‐ligand MOF (COF‐on‐MOF) upon appropriate exposure illumination. Notably, the interplay between light and COF‐on‐MOF can adjust the device physics, optimizing the I_On/I_Off to its maximum and enhancing signal transduction. Toward bio‐application, via exonuclease‐assisted cyclic cleavage amplification and hybridization chain reaction, such a device is validated for highly sensitive detection capabilities for human T‐cell lymphotropic virus type II (HTLV‐II) DNA down to 0.003 fM. This study features the possibility of Ag/AgCl‐like photogating of organic transistors via light‐matter interplay.