Singlet exciton fission (SF), the conversion of one spin-singlet exciton (S₁) into two spin-triplet excitons (T₁), could provide a means to overcome the Shockley–Queisser limit in photovoltaics. SF as measured by the decay of S₁ has been shown to occur efficiently and independently of temperature, even when the energy of S₁ is as much as 200 meV less than that of 2T₁. Here we study films of triisopropylsilyltetracene using transient optical spectroscopy and show that the triplet pair state (TT), which has been proposed to mediate singlet fission, forms on ultrafast timescales (in 300 fs) and that its formation is mediated by the strong coupling of electronic and vibrational degrees of freedom. This is followed by a slower loss of singlet character as the excitation evolves to become only TT. We observe the TT to be thermally dissociated on 10–100 ns timescales to form free triplets. This provides a model for ‘temperature-independent’ efficient TT formation and thermally activated TT separation.

中文翻译：

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纤维相干超快三重态对的形成和随后的热活化解离控制有效的吸热单线态裂变

单重态激子裂变（SF），一种自旋-单重态激子（S ₁）到两个自旋-三重态激子（T ₁）的转化，可以提供一种克服光伏中肖克利-奎塞尔极限的方法。通过S ₁的衰变测量的SF已被证明有效且独立于温度而发生，即使S ₁的能量比2T ₁的能量小200 meV。。在这里，我们使用瞬态光谱学研究了三异丙基甲硅烷基并四苯的薄膜，结果表明，被提议来介导单重态裂变的三重对态（TT）以超快的时间尺度（在300 fs内）形成，并且其形成是由三氟甲烷的强耦合介导的。电子和振动自由度。随后，随着激发演变为仅变成TT，单重态字符的损失会更慢。我们观察到TT在10-100 ns的时间尺度上热解离形成自由三重态。这为“与温度无关”的高效TT形成和热活化TT分离提供了模型。