Electronic State Engineering in Perovskite-Cerium-Composite Nanocrystals toward Enhanced Triplet Annihilation Upconversion

Wavelength conversion based on hybrid inorganic-organic sensitized triplet-triplet annihilation upconversion (TTA-UC) is promising for applications such as photovoltaics, light-emitting-diodes, photocatalysis, additive manufacturing, and bioimaging. The efficiency of TTA-UC depends on the population of triplet excitons involved in triplet energy transfer (TET), the driving force in TET, and the coupling strength between the donor and acceptor. Consequently, achieving highly efficient TTA-UC necessitates the precise control of the electronic states of inorganic donors. However, conventional covalently bonded nanocrystals (NCs) face significant challenges in this regard. Herein, a novel strategy to exert control over electronic states is proposed, thereby enhancing TET and TTA-UC by incorporating ionic-bonded CsPbBr3 and lanthanide Ce3+ ions into composite NCs. These composite-NCs exhibit high photoluminescence quantum yield, extended single-exciton lifetime, quantum confinement, and uplifted energy levels. This engineering strategy of electronic states engendered a comprehensive impact, augmenting the population of triplet excitons participating in the TET process, enhancing coupling strength and the driving force, ultimately leading to an unconventional, dopant concentration-dependent nonlinear enhancement of UC efficiency. This work not only advances fundamental understanding of hybrid TTA-UC but also opens a door for the creation of other ionic-bonded composite NCs with tunable functionalities, promising innovations for next-generation optoelectronic applications. It is discovered that electronic state engineering of perovskite nanocrystals leads to size focusing with greatly increased fluorescent quantum yield. This strategy can control triplet population, energy-level alignment, and exciton lifetime, which significantly enhanced triplet-triplet annihilation upconversion (TTA-UC) efficiency (approximate to 284%). This work clarifies the functions of electronic state engineering for inorganic sensitizers and TTA-UC. It will promote the fundamental research of electronic state engineering in energy transfer systems and facilitate the practical applications of TTA-UC systems.image

Automated summary

This study proposes a novel strategy to enhance triplet-triplet annihilation upconversion (TTA-UC) by incorporating ionic-bonded CsPbBr3 and lanthanide Ce3+ ions into composite nanocrystals. This electronic state engineering increases the population of triplet excitons participating in energy transfer, enhances coupling strength and driving force, and ultimately leads to a nonlinear enhancement of UC efficiency. The findings clarify the functions of electronic state engineering in inorganic sensitizers and TTA-UC.