Paired-TFT Reconfigurable Architecture with Photosensitive Heterojunction Layer for Logic Operations and Color Recognition

Multifunctional and reconfigurable optoelectronic circuits capable of performing both logic operations and wavelength-dependent sensing are essential for the development of adaptive electronic systems. An optoelectronic platform is proposed that consisting of only two serially connected thin-film transistors (TFTs), where one is a wide-bandgap ZTO TFT and the other is a narrow-bandgap Ag_xO/ZTO heterojunction TFT. By applying appropriate gate biases, the circuit enables logic operations, including NAND and NOR gates, without the need for additional transistors. Uniquely, instead of conventional photocurrent-based detection, which often suffers from ambiguity when weak short-wavelength light and strong long-wavelength light irradiate the photodetector and induce similar photocurrent magnitudes, the architecture distinguishes the wavelength of LASER via the output voltage (V_out) extracted from the intermediate node between the two TFTs. Under fixed biasing and illumination by 405, 520, and 670 nm LASER, V_out exhibits wavelength-dependent variations that correspond to a photo-modulated voltage division. These responses are consistently explained by the distinct light absorption and resistance modulation of each TFT. This voltage-based sensing strategy overcomes limitations of photocurrent degeneracy and enables reliable color recognition within the same paired-TFT architecture. The integration of logic operations and optical discrimination within a series-integrated architecture offers a promising route toward reconfigurable optoelectronic systems.