Polarization‐Sensitive Photodetectors Based on Directionally Oriented Organic Bulk‐Heterojunctions

Abstract Polarized spectroscopic photodetection enables numerous applications in diverse areas such as sensing, industrial quality control, and visible light communications. Although organic photodetectors (OPDs) can offer a cost‐effective alternative to silicon‐based technology—particularly when flexibility and large‐area arrays are desired—polarized OPDs are only beginning to receive due research interest. Instead of resorting to external polarization optics, this report presents polarized OPDs based on directionally oriented blends of poly(3‐hexylthiophene) (P3HT) and benchmark polymer or nonfullerene acceptors fabricated using a versatile solution‐based method. Furthermore, a novel postprocessing scheme based on backfilling and plasma etching is advanced to ameliorate high dark‐currents that are otherwise inherent to fibrillar active layers. The resulting polarized P3HT:N2200 OPDs exhibit a broad enhancement across all principal figures of merit compared to reference isotropic devices, including peak responsivities of 70 mA W −1 and up to a threefold increase in 3 dB bandwidth to 0.75 MHz under parallel‐polarized illumination. Polarization ratios of up to 3.5 are obtained across a spectral range that is determined by the specific donor–acceptor combinations. Finally, as a proof‐of‐concept demonstration, polarized OPDs are used for photoelasticity analysis of rubber films under tensile deformation, highlighting their potential for existing and emerging applications in advanced optical sensing.