Boosting Performance of Self‐Powered Near‐Infrared Organic Spectral Detector Through Metal–Dielectric Microcavity

Abstract Miniaturized spectrometers that are absent of bulky dispersive optical elements have received more and more attention. However, most of these advancements have been demonstrated in the visible spectrum. Among the various near‐infrared (NIR) absorbers, organic donor–acceptor blends exhibit a distinctive red‐shifted intermolecular charge‐transfer (CT) state absorption, allowing for the detection of NIR photons below the distinct molecular band edge. Nevertheless, the sub‐bandgap absorption cross‐section has been rather limited. In this study, this challenge is addressed by integrating a metal–dielectric (M–D) microcavity into a prototype (PM6:Y6) model system, with a band‐edge positioned at 869 nm. As a result, an amplified narrowband detection, demonstrating an external quantum efficiency of ≈26% at 905 nm is achieved. Furthermore, the manipulation of the cavity lengths enables easy fine‐tuning of the narrowband spectral response within the 850–960 nm range. Leveraging a spectrum reconstruction algorithm, a spectral detector with 10 nm resolution under a zero bias, validating the potential of utilizing sub‐bandgap CT state absorption for efficient narrowband detectors and micro‐spectrometers is obtained.