Geminate Delayed Fluorescence by Anisotropic Diffusion-Mediated Reversible Singlet Fission and Triplet Fusion
Geminate Delayed Fluorescence by Anisotropic Diffusion-Mediated Reversible Singlet Fission and Triplet Fusion
复制标题
各向异性扩散介导的可逆单线态裂变和三线态融合产生双子延迟荧光
DOI：
10.1021/acs.jpcc.0c10582
复制
发表时间：
2021
影响因子：
3.7
通讯作者：
and Ryuzi Katoh
中科院分区：
文献类型：
--
作者：
Kazuhiko Seki;Tomomi Yoshida;Tomoaki Yago;Masanobu Wakasa;and Ryuzi Katoh
单线态裂变（SF）发生在分子固体中，有望通过将激子或电荷转移到低带隙半导体中来提高光子到电子的转换效率。必须阐明三态融合的基本过程及其逆向过程，以表征三态融合对转换效率的影响。如果在同一对中，TF发生在SF之后，则一定比例的激发单重态可以被TF再生，甚至可能反复发生。因此，被激发的单线态通过三联体的双态融合表现出延迟的荧光。在本研究中，我们证明了双态延迟荧光的渐近幂律衰减中的指数反映了扩散的各向异性。在分子晶体中，最大和最小激子扩散常数之比的差异可以达到数量级。通过比较理论结果和四烯和rubrene的荧光衰减，我们估计了这些材料中三重态扩散常数的各向异性范围。我们还表明，对于三重态扩散常数的各向异性比率的某些值，幂律衰减指数随时间而变化。
Singlet fission (SF) occurs in molecular solids and is expected to increase the conversion efficiency of photons into electrons by transferring excitons or charges into low-band-gap semiconductors. The fundamental processes of SF and its reverse process of triplet fusion (TF) would have to be elucidated to characterize the effect of SF on the conversion efficiency. In situations in which TF occurs subsequent to SF within the same pair, a certain fraction of the excited singlets could be regenerated by TF and this may even happen repeatedly. Consequently, the excited singlets exhibit delayed fluorescence by geminate fusion of the triplets. In this study, we show that the exponent in the asymptotic power law decay of the geminate delayed fluorescence reflects the diffusional anisotropy. In molecular crystals, the difference in the ratio between the largest and smallest exciton diffusion constants can be orders of magnitude. By comparing the theoretical results and the fluorescence decay in tetracene and rubrene, we estimated the range of anisotropy in the triplet diffusion constants in these materials. We also show that the exponent of the power law decay changes as a function of time for certain values of the anisotropy ratio in the triplet diffusion constants.