An energetics perspective on why there are so few triplet–triplet annihilation emitters
An energetics perspective on why there are so few triplet–triplet annihilation emitters
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DOI：
10.1039/d0tc00044b
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发表时间：
2020-03
影响因子：
6.4
通讯作者：
Xiaopeng Wang;Rithwik Tom;Xingyu Liu;Daniel N. Congreve;N. Marom
中科院分区：
文献类型：
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作者：
Xiaopeng Wang;Rithwik Tom;Xingyu Liu;Daniel N. Congreve;N. Marom
太阳能电池的效率可以通过利用能量低于吸收体的带隙的光子来增加。这可以通过在有机发色团中经由三重态-三重态湮灭（TTA）将低能光子上转换成高能光子来实现。由于竞争过程，TTA的量子产率通常较低。单重态路径，其中发射出高能量光子，是两个三重态激子之间相遇的三种可能结果之一。五联体途径的能量通常太高而无法进入，留下三联体途径作为主要的竞争过程。利用GW近似下的多体微扰理论和Bethe-Salpeter方程，计算了59种不同化学族的发色团的单重态和三重态能量释放.我们发现，在大多数情况下，三重态途径是开放的，并有一个更大的能量释放比单重态途径。因此，从能量学的角度解释了为什么TTA发射体如此之少，以及为什么TTA的量子产率通常很低。也就是说，我们的研究结果还表明，来自已知化学家族的发射体的性能可以通过化学修饰来改善，例如用侧基官能化，并且可以探索新的化学家族以发现更多的TTA发射体。
The efficiency of solar cells may be increased by utilizing photons with energies below the band gap of the absorber. This may be enabled by upconversion of low energy photons into high energy photons via triplet–triplet annihilation (TTA) in organic chromophores. The quantum yield of TTA is often low due to competing processes. The singlet pathway, where a high energy photon is emitted, is one of three possible outcomes of an encounter between two triplet excitons. The quintet pathway is often too high in energy to be accessible, leaving the triplet pathway as the main competing process. Using many-body perturbation theory in the GW approximation and the Bethe–Salpeter equation, we calculate the energy release in both the singlet and triplet pathways for 59 chromophores of different chemical families. We find that in most cases the triplet pathway is open and has a larger energy release than the singlet pathway. Thus, the energetics perspective explains why there are so few TTA emitters and why the quantum yield of TTA is typically low. That said, our results also indicate that the performance of emitters from known chemical families may be improved by chemical modifications, such as functionalization with side groups, and that new chemical families could be explored to discover more TTA emitters.