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

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.