Single-pixel spectrometer based on a bias-tunable tandem organic photodetector

Summary

Miniaturized computational spectrometers enable compact, lightweight sensing using a modulated spectral response and reconstruction algorithm. We present an organic photodetector (OPD)-based spectrometer that leverages complementary spectral responses of target organic semiconductors (D18-Cl, L8BO, PTB7-Th, and COTIC-4F) in a tandem cell design. The sub-cells have opposing polarity, causing a bias-tunable spectral response, resulting in a spectrometer sensitive to wavelengths ranging from ultraviolet to near infrared (400–1,000 nm). Through sweeping external bias, the photoresponse enables the reproduction of both narrow and broad-spectrum incident light. The detector demonstrates responsivity of 0.27 A W⁻¹, detectivity of 1.4 × 10¹² Jones, and a rise/fall time of 2.82/3.72 μs while operating at voltages of less than 1 V. The tandem OPD-spectrometer design realizes high-performance imaging spectrometers without the need for external gratings or filters, with applications in portable and integrated micro-spectrometers.