Bright and Ultralong Organic Phosphorescence via Sulfonic Acid Functionalization for High-Contrast Real-Time Light-Writing Display

It is challenging to achieve room-temperature phosphorescence (RTP) in pure organics with both high efficiency and long lifetime. While much effort has been placed on discovering efficient phosphor skeletons, the importance of phosphor functionalization in enhancing the RTP performance has not received adequate attention. Herein, we demonstrate that functionalization of phosphors with sulfonic acid can ensure both bright and ultralong RTP, outperforming other substituents. The unique trigonal pyramidal structure of sulfonic acid group allows for more effective (n, π*) transitions to enhance intersystem crossing efficiency. Its highly polarized S-O bonds render strengthened hydrogen bonding interactions and a narrower confinement within the poly(vinyl alcohol) (PVA) matrix, to minimize the nonradiative dissipation. Furthermore, its excellent water solubility contributes to the outstanding transparency of PVA film (over 97%), yielding high-quality optical imaging with a high contrast ratio of 48.0 and a low blurriness of 0.24. Moreover, full-color phosphorescence with exceptional performance (Φ_{P, max} = 37.2%, τ_{P, max} = 2.09 s) is achieved from different sulfonic acids, validating the effectiveness and universality of this strategy. By leveraging these advantages, real-time light-writing displays with sharp imaging, high sensitivity, and exceptional rewritability are demonstrated. This work not only contributes to the substituent engineering in the molecular design of phosphors but also opens new opportunities for RTP materials in the next-generation intelligent optoelectronic materials.