PffBT4T

Conformational and energetic disorder in organic semiconductors reduces charge and exciton transport because of the structural defects, thus reducing the efficiency in devices such as organic photovoltaics and organic light-emitting diodes. The main structural heterogeneity is because of the twisting of the polymer backbone that occurs even in polymers that are mostly crystalline. Here, we explore the relationship between polymer backbone twisting and exciton delocalization by means of transient absorption spectroscopy and density functional theory calculations. We study the PffBT4T-2DT polymer which has exhibited even higher device efficiency with nonfullerene acceptors than the current record breaking PCE11 polymer. We determine the driving force for planarization of a polymer chain caused by excitation. The methodology is generally applicable and demonstrates a higher penalty for nonplanar structures in the excited state than in the ground state. This study highlights the morphologic...

有机半导体中的构象与能量无序会因结构缺陷抑制电荷与激子（exciton）的输运过程，进而降低有机光伏（organic photovoltaics）、有机发光二极管（organic light-emitting diodes）等器件的工作效率。该类材料的主要结构异质性源于聚合物主链的扭转，即便在多数呈结晶态的聚合物中也会出现此类扭转。本研究借助瞬态吸收光谱法（transient absorption spectroscopy）与密度泛函理论（density functional theory）计算，探究了聚合物主链扭转与激子离域化之间的内在关联。我们选取PffBT4T-2DT聚合物作为研究对象，该聚合物搭配非富勒烯受体（nonfullerene acceptors）时展现出的器件能效，甚至超越了当前破纪录的PCE11聚合物。我们明确了激发作用引发的聚合物链平面化驱动力；该研究方法具备普适性，且证实激发态中非平面结构的能量代价高于基态。本研究着重揭示了形态学（morphologic）……