Electrically Coded Retinomorphic Spectrophotodetector

Accurate color sensing is essential for applications ranging from materials analysis to autonomous vision, yet compact systems that can classify color directly at the device level without bulky optics or computationally intensive post-processing remain limited. Here, a machine learning-free, self-powered retinomorphic pyro-photodetector is demonstrated for direct electrical wavelength encoding from 365 to 940 nm. The multiterminal Ag/ZnO/n-Si/Ag device uses electrostatically balanced built-in potentials to convert incident wavelength into distinct photo and pyroelectric current fingerprints, enabling direct in-sensor spectral discrimination without spectral reconstruction and external neural processing. The device achieves wavelength decoding with less than 3 nm accuracy and a pyroelectric current rise-time of ∼46 µs. At the system level, direct in-sensor encoding enables end-to-end wavelength classification with 300 ms latency while reducing downstream energy and computational complexity. The encoded electrical readout enables accurate color classification and is further applied to plant health and pigment-state sensing, as well as quantification of 0% to 40% water adulteration in milk, curd, coconut water, and salt and sugar solutions, with classification accuracy above 92%. This work establishes a portable retinomorphic platform for real-time, energy-efficient, and high-precision spectral sensing, providing a general route toward direct in-sensor color recognition and wavelength classification.