Wieghold Sarah, Bieber Alexander S, VanOrman Zachary A, Nienhaus Lea
Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306 , United States.
J Phys Chem Lett. 2019 Jul 5;10(13):3806-3811. doi: 10.1021/acs.jpclett.9b01526. Epub 2019 Jun 25.
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 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.
卤化铅钙钛矿敏化红荧烯中的三线态-三线态湮灭（TTA）这一新兴领域在光上转换应用中显示出巨大潜力。通过快速转移单电荷载流子而非束缚三线态，钙钛矿能在红荧烯中实现高三线态布居数，从而得到低I值。在本论文中，我们研究了三线态布居数对光上转换发射的作用。有趣的是，可以观察到两个独立的TTA速率，以及可见光发射强度在数秒内急剧下降。这种效应可归因于基于三线态密度的扩散长度：（i）在低三线态布居数时，缓慢的扩散介导TTA在远离界面处产生单线态；（ii）较高的三线态布居数导致在钙钛矿/红荧烯界面附近快速发生TTA。由于强吸收性钙钛矿的临近，在靠近界面处产生的单线态向钙钛矿薄膜的反向转移更强，因此似乎表现出较低的光致发光量子产率。
