Resonant Cavity‐Enhanced Intermolecular Charge‐Transfer Absorption for Near‐Infrared Photon Upconversion and Single‐Detector Imaging

Abstract

ABSTRACT Organic semiconductors offer compelling advantages for facile and scalable optoelectronic integration, yet their limited absorption range constrains their applicability in near‐infrared (NIR) photonic technologies. Here, we report an organic upconversion device (OUD) that effectively harnesses the inherently weak but spectrally broad charge‐transfer (CT) absorption to convert NIR radiation into visible light. A resonant optical microcavity is strategically engineered to selectively amplify the CT absorption band and to establish optical isolation between the organic photodetector (PD) and the organic light‐emitting diode, thereby enhancing light‐coupling efficiency while suppressing reabsorption losses. The device achieves an impressive P–P conversion efficiency of 16.9% under 980 nm NIR illumination, despite the constituent materials lacking intrinsic absorption at this wavelength. Moreover, by simply adjusting the cavity thickness, an efficient OUD operating at a detection wavelength of 1550 nm is successfully developed for the first time. In addition, single‐detector NIR imaging is demonstrated using large‐area devices equipped with dot‐matrix connecting electrodes (DMCEs) without needing complex readout integrated circuits (ROICs) to scan signals. This work unveils the potential of intermolecular CT absorption as a versatile platform for applications in NIR sensing, upconversion, and imaging.