High-performance narrowband cavity organic photodetectors enabled by a polystyrene doping strategy

Conventional cavity-enhanced organic photodetectors (OPDs) often suffer from broad spectral response due to the high absorption coefficient of the organic active layer, which compromises cavity selectivity. To overcome this issue, the authors propose a novel and effective strategy: incorporating polystyrene (PS) into the PTB7-Th:PC61BM bulk heterojunction active layer of a Fabry–Pérot cavity OPD. The PS doping reduces the effective absorption coefficient of the optical cavity without requiring an ultra-thin active layer, thereby narrowing the spectral response. Utilizing this approach with an optimized 30% PS doping ratio, the fabricated devices demonstrate significantly improved performance. Notably, a device exhibits a narrow full width at half maximum of 49 nm, a high external quantum efficiency exceeding 40% at the resonance wavelength, and a specific detectivity (D*) surpassing 1.0 × 1013 Jones. This performance is comparable to commercial silicon-based photodetectors, showcasing the potential of this PS-doping strategy for developing high-performance, tunable narrowband OPDs.