A Bias-Tunable Pseudo-Planar Heterojunction Organic Photodetector for Single-Pixel Computational Spectrometer and Filterless Color Sensor

The pursuit of miniaturized spectrometers necessitates device architectures that are both structurally simple and high-performing. This work reports a single-pixel organic computational spectrometer (OCS) based on an organic photodetector (OPD) with a pseudoplanar heterojunction (PPHJ) active layer. Through controlled sequential deposition, a gradient donor–acceptor distribution is achieved, yielding bias-dependent spectral responses with strong nonlinear correlations (Pearson correlation coefficients from −0.07 to 1.00). The OCS achieves a high detectivity of 7.84 × 1012 Jones and a fast response time of 2.85 μs, enabling accurate reconstruction of monochromatic and broadband spectra across 300–1000 nm range with a normalized root-mean-square error (NRMSE) as low as 0.0034. Moreover, the same device structure serves as a filterless quad-channel color sensor via photocurrent readout at four predefined bias voltages, bypassing the need for spectral filters or complex algorithms. This minimalist design, which delivers high performance from a single active layer, offers significant potential for portable and integrated spectroscopic applications.