论文标题
通过瞬态激子离域介导的有机半导体中的有效能量传输
Efficient Energy Transport in an Organic Semiconductor Mediated by Transient Exciton Delocalization
论文作者
论文摘要
高效的能量传输非常需要有机半导体（OSC）设备，例如光伏，光电探测器和光催化系统。但是，OSC膜中的照片生成的激子在其一生中大多占据了高度本地化的状态。因此，能量传输被认为主要是由局部激子的位置跳跃介导的，将激子扩散系数限制在〜10^{ - 2} cm^2/s以下，其相应的扩散长度低于〜50 nm。在这里，使用超快光学显微镜结合非绝热分子动力学模拟，我们提供了新的高效能量传输状态的证据：瞬态激烈的激子Deciton Decalization，在平衡条件下，具有振动模式的能量交换允许振动模式在空间延伸状态下暂时重新获得空间延伸状态。在使用活性结晶驱动的自组装制备的高度排序的聚（3-己基噻吩）纳米纤维的膜中，我们表明，这使激子扩散常数高达1.1+-0.1 cm^2/s，并且扩散长度为300+-50 Nm。我们的结果揭示了在平衡条件下局部和离域的激子配置之间的动态相互作用，呼吁重新评估激子动力学的基本图片。这为OSC膜中的工程师有效的能源运输建立了新的设计规则，该规则将使新设备架构不基于限制性散装异质界化。
Efficient energy transport is highly desirable for organic semiconductor (OSC) devices such as photovoltaics, photodetectors, and photocatalytic systems. However, photo-generated excitons in OSC films mostly occupy highly localized states over their lifetime. Energy transport is hence thought to be mainly mediated by the site-to-site hopping of localized excitons, limiting exciton diffusion coefficients to below ~10^{-2} cm^2/s with corresponding diffusion lengths below ~50 nm. Here, using ultrafast optical microscopy combined with non-adiabatic molecular dynamics simulations, we present evidence for a new highly-efficient energy transport regime: transient exciton delocalization, where energy exchange with vibrational modes allows excitons to temporarily re-access spatially extended states under equilibrium conditions. In films of highly-ordered poly(3-hexylthiophene) nanofibers, prepared using living crystallization-driven self-assembly, we show that this enables exciton diffusion constants up to 1.1+-0.1 cm^2/s and diffusion lengths of 300+-50 nm. Our results reveal the dynamic interplay between localized and delocalized exciton configurations at equilibrium conditions, calling for a re-evaluation of the basic picture of exciton dynamics. This establishes new design rules to engineer efficient energy transport in OSC films, which will enable new devices architectures not based on restrictive bulk heterojunctions.
