Enhancing Photon–Photon Efficiency of Semi‐Transparent Organic Upconversion Devices via Photon Management for Pixel‐Free Near‐Infrared Imaging

Abstract Organic upconversion devices (UCDs) play significant roles in converting near‐infrared (NIR) light into visible light with advantages of pixel‐free and low‐power. Compared to opaque UCDs, semi‐transparent upconversion devices (ST‐UCDs) can be fabricated into see‐through displays, making them highly suitable for applications like night vision. However, conventional ST‐UCDs suffer from > 50% photon loss due to isotropic visible light emission, limiting their photon–photon conversion efficiency ( η p‐p ). In this work, a high‐pass filter (HPF) integration strategy is introduced that redirects anode‐escaping photons toward the semi‐transparent cathode via Fabry–Pérot interference. This approach achieves η p‐p = 1.05% (1.6× enhancement over controls) and enables pixel‐free NIR imaging with 2.5 lp mm −1 resolution. The synergy between optical field management and organic photonic design opens new avenues for boosting the performance of ST‐UCDs and can also be extended to other organic optoelectronic systems.