By upconverting unused, low energy photons from the red spectral region to higher energy photons through a process of triplet-triplet annihilation (TTA), the overall power conversion efficiency of photovoltaic cells can be increased. This presentation will describe an energy upconversion system in which two dyes are bound to the same ZnO or ZrO2 nanocrystals via carboxylate anchors. The dye-decorated nanocrystals are dispersed in solution to facilitate detailed kinetic studies using ultrafast pump-probe spectroscopy. The sensitizer is a strongly absorbing bodipy derivative bearing two iodo substituents to increase the efficiency of intersystem crossing to the triplet state. The emitter dye is a perylene derivative whose singlet excited state is sufficiently high to inject directly into the ZnO conduction band but not into the higher energy conduction band of the ZrO2 nanocrystals. Photon upconversion quantum yields on the ZrO2 will be reported. Electron transfer quenching of the singlet excited state of the perylene dye by ZnO nanocrystals is demonstrated.

Energy upconversion leading to excited state electron transfer to ZnO nanocrystals

ACS Spring 2022

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