Organic semiconductors usually exhibit low structural-order owing to their weak intermolecular interactions, which leads to inferior charge transport and strong carrier recombination in photovoltaics. In this work, three thiophene structured solid additives namely thieno[3,2-b]thiophene (TT), 3,6-dibromothieno[3,2-b]thiophene (TTBB) and 3-bromo-6-iodio-thieno[3,2-b]thiophene (TTBI) are utilized to enhance the molecular interactions in a range of electron donors and acceptors. X-ray technique and molecular dynamics simulations reveal that by adjusting their electrostatic potential and dipole moment, their interacting site and interaction energy with donor (PM6 and D18) or acceptor (L8-BO) can be finely tuned. We find the most electropositive TTBB shows the strongest interaction with PM6, leading to enhanced crystallization; whilst the asymmetric TTBI brings the strongest molecular packing of L8-BO, consequent to more compact π-π stacking and ordered alkyl chain packing. As the results, the bulk heterojunction PM6:L8-BO photovoltaics upon the assistance of TTBI or TTBB obtain improved charge transport and reduced non-radiative energy loss, translating to power conversion efficiency (PCE) values of 18.7 % and 19.1 %. When further taking the synergetic effect of TTBB and TTBI on PM6(D18) and L8-BO respectively, the layer-by-layer deposited PM6(TTBB)/L8-BO(TTBI) and D18(TTBB)/L8-BO(TTBI) allowed superior PCEs of 19.4 % and 19.9 %, which are among the highest values of single-junction organic solar cells.

中文翻译：

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噻吩结构添加剂可增强结构秩序并减少非辐射损耗，实现 19.9% 效率的有机太阳能电池


由于分子间相互作用较弱，有机半导体通常表现出低结构有序性，这导致光伏发电中的电荷传输较差和载流子复合较强。在这项工作中，三种噻吩结构的固体添加剂，即噻吩并[3,2-b]噻吩（TT）、3,6-二溴噻吩并[3,2-b]噻吩（TTBB）和3-溴-6-碘噻吩[ 3,2-b]噻吩 (TTBI) 用于增强一系列电子供体和受体中的分子相互作用。 X射线技术和分子动力学模拟表明，通过调整它们的静电势和偶极矩，可以微调它们与供体（PM6和D18）或受体（L8-BO）的相互作用位点和相互作用能。我们发现电正性最强的 TTBB 与 PM6 的相互作用最强，导致结晶增强；而不对称TTBI带来了最强的L8-BO分子堆积，从而导致更紧凑的π-π堆积和有序烷基链堆积。结果，本体异质结 PM6:L8-BO 光伏电池在 TTBI 或 TTBB 的帮助下获得了改善的电荷传输和减少的非辐射能量损失，转化为 18.7% 和 19.1% 的功率转换效率 (PCE) 值。当进一步发挥TTBB和TTBI分别对PM6(D18)和L8-BO的协同作用时，逐层沉积的PM6(TTBB)/L8-BO(TTBI)和D18(TTBB)/L8-BO(TTBI) ）实现了 19.4% 和 19.9% 的优异 PCE，这是单结有机太阳能电池的最高值之​​一。