High Photon Upconversion Efficiency with Hybrid Triplet Sensitizers by Ultrafast Hole-Routing in Electronic-Doped Nanocrystals

摘要: Low power photon upconversion (UC) based on sensitized triplet-triplet annihilation (sTTA) is considered as the most promising upwards wavelength-shifting technique to enhance light harvesting capability of solar devices by recovering low-energy tail spectrum. Semiconductor nanocrystals (NCs) with conjugated organic ligands have been proposed broadband sensitizers for extending light-harvesting sTTA-UC molecular absorbers. Key their functioning efficient energy transfer (ET) from NC triplet state that sensitizes free emitters, whose generates upconverted emission. To date, sensitization efficiency in such systems limited parasitic processes, charge (typically photohole) ligand due disadvantageous band alignment typical NCs and moieties. Available strategies only partially mitigate losses intrinsically limit ET yield. Here we demonstrate a new exciton-manipulation approach enables loss-free without detrimental side-effects. Specifically, use CdSe doped gold atoms featuring hole-accepting bandgap at higher than HOMO level 9-anthracene acid. Upon photoexcitation, photoholes are routed Au-state faster ligand, producing long-lived bound exciton perfect resonance its state. This hinders hole-transfer results ~100% ET, over 50-fold standard NCs. By combining our hybrid an annihilator moiety, achieved ~12% (~24% normalized definition), which highest value upconverters sTTA reported date approaches optimized systems.