Temperature-Dependent Recombination of Triplet Biexcitons in Singlet Fission of Hexacene
Temperature-Dependent Recombination of Triplet Biexcitons in Singlet Fission of Hexacene
复制标题
DOI：
10.1021/acs.jpcc.1c10691
复制
发表时间：
2022-05
期刊：
影响因子：
--
通讯作者：
Yuqin Qian;Zhi-Chao Huang-Fu;Tong Zhang;Xia Li;A. Harutyunyan;Gugang Chen;Hanning Chen;Y. Rao
中科院分区：
文献类型：
--
作者：
Yuqin Qian;Zhi-Chao Huang-Fu;Tong Zhang;Xia Li;A. Harutyunyan;Gugang Chen;Hanning Chen;Y. Rao
单线态裂变是一种自旋守恒过程，通过吸收一个光子，将一个单线态激子倍增转化为两个独立的三重态激子。这样的乘法被认为可以规避肖克利-奎瑟热力学极限，从而提高太阳能转换效率。了解单线态裂变材料产生三重态激子的机理和产率对有效利用太阳能至关重要。在这里，我们采用温度依赖的瞬态吸收光谱来研究六正体中单线态裂变和三重态激子的动力学性质。从77 K到室温，中间相关双激子1（TT）的生成和解离速率与温度无关。另一方面，空间分离的双激子1（T···T）中的三重态激子通过双态和非双态重组而松弛。前者与温度有关，而后者与温度无关。定量分析两种复合过程的温度相关速率，得到1（T···T）和1（TT）之间的能量差，并通过密度泛函理论（DFT）计算进一步证实了这一点。
Singlet fission is a spin-conserving process for the multiplication conversion of one singlet exciton into two individual triplet excitons by absorbing one photon. Such a multiplication is believed to circumvent the Shockley–Queisser thermodynamic limit for improving efficiency of solar energy conversion. A mechanistic understanding of generation and yields of triplet excitons from singlet fission materials is essential for efficient exploitation of solar energy. Here we employ temperature-dependent transient absorption spectroscopy to examine the dynamical nature of singlet fission and triplet excitons in hexacene. The generation and dissociation rates of the intermediate correlated biexciton,1(TT), are independent of temperature from 77 K to the room temperature. On the other hand, the triplet excitons in spatially separated biexcitons,1(T···T), relax via geminate and nongeminate recombination. The former was found to be temperature-dependent, whereas the latter is temperature-independent. Quantitative analyses of the temperate-dependent rates for the two recombination processes yield the energy difference between the1(T···T) and1(TT), which were further confirmed by our density functional theory (DFT) calculations.