© 2017 Society of Photo-Optical Instrumentation Engineers (SPIE). Improving efficiency of triplet-triplet annihilation-based photon upconversion (TTA-UC) in crystalline media is challenging because it usually suffers from the severe aggregation of the donor (sensitizer) molecules in acceptor (emitter) crystals. We show a kinetically controlled crystal growth approach to improve donor dispersibility in acceptor crystals. As the donor-acceptor combination, a benchmark pair of platinum(II) octaethylporphyrin (PtOEP) and 9,10-diphenylanthracene (DPA) is employed. A surfactant-assisted reprecipitation technique is employed, where the concentration of the injected PtOEP-DPA solution holds the key to control dispersibility; at a higher PtOEP-DPA concentration, a rapid crystal growth results in better dispersibility of PtOEP molecules in DPA crystals. The improvement of donor dispersibility significantly enhances the TTA-UC quantum yield. Thus, the inherent function of donor-doped acceptor crystals can be maximized by controlling the crystallization kinetics.
Ogawa, T., Yanai, N., Kouno, H., & Kimizuka, N. (2017). Kinetically controlled crystal growth approach to enhance triplet energy migration-based photon upconversion. Journal of Photonics for Energy, 8(02), 1. https://doi.org/10.1117/1.jpe.8.022003