Influence of Triplet Diffusion on Lead Halide Perovskite-Sensitized Solid-State Upconversion

• Published in: The journal of physical chemistry letters Vol. 10; no. 13; pp. 3806 - 3811
• Main Authors: Wieghold, Sarah, Bieber, Alexander S, VanOrman, Zachary A, Nienhaus, Lea
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 05.07.2019
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.9b01526

The emerging field of lead halide perovskite-sensitized triplet–triplet annihilation (TTA) in rubrene shows great promise in upconversion applications. By rapidly transferring single charge carriers instead of bound triplet states, perovskites enable a high triplet population in rubrene, yielding low I th values. In this contribution, we investigate the role of the triplet population on the upconverted emission. Interestingly, two independent rates of TTA can be observed, as well as a sharp drop in the visible emission intensity over several seconds. This effect can be attributed to the triplet-density-based diffusion length: (i) at low triplet populations slow diffusion-mediated TTA yields singlets far from the interface and (ii) higher triplet populations lead to rapid TTA close to the perovskite/rubrene interface. Because of the proximity of the strongly absorbing perovskite, the singlet states created closer to the interface undergo stronger back-transfer to the perovskite film and therefore appear to exhibit a lower photoluminescence quantum yield.