A new non-fullerene small molecule with an acceptor-donor-acceptor (A-D-A) structure, FDNCTF, incorporating fluorenedicyclopentathiophene as core and naphthyl-fused indanone as end groups, was designed and synthesized. Compared with the previous molecule FDICTF with the phenyl-fused indanone as the end groups, the extended π-conjugation at the end group has only little impact on its molecular orbital energy levels, and thus, the open-circuit voltage (V_oc) of its solar cell devices has been kept high. However, its light absorption and mobility, together with the short-current density (J_sc) and the fill factor (FF), of its devices have been all improved simultaneously. Through morphology, transient absorption, and theoretical studies, it is believed that these favorable changes are caused by (1) the appropriately enhanced molecular interaction between donor/acceptor which makes the charge separation at the interface more efficient, and (2) enhanced light absorption and more ordered packing at solid state, all due to the extended end-group conjugation of this molecule. With these, the solar cells with FDNCTF as the acceptor and a wide band gap polymer PBDB-T as the donor demonstrated a high power conversion efficiency (PCE) of 11.2% with an enhanced J_sc and a maintained high V_oc, and significantly improved FF of 72.7% compared with that of the devices of FDICTF with the phenyl-fused indanone as the end groups. These results indicate that the unexplored conjugation size of the end group plays a critical role for the performance of their solar cell devices.

中文翻译：

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具有末端扩展共轭的ADA型小分子电子受体，用于高性能有机太阳能电池

设计并合成了一种新的具有受体-供体-受体（ADA）结构的非富勒烯小分子FDNCTF，其以氟代二环戊噻吩为核心，萘基稠合的茚满酮为端基。与以前的以苯基稠合的茚满酮为端基的分子FDICTF相比，在端基上扩展的π共轭对其分子轨道能级的影响很小，因此，其开路电压（V _oc）很小。它的太阳能电池装置一直保持很高的状态。然而，它的光吸收和迁移率以及短电流密度（J _sc）及其填充因子（FF）均同时得到了改善。通过形态学，瞬态吸收和理论研究，认为这些有利的变化是由于（1）供体/受体之间适当增强的分子相互作用而使界面处的电荷分离更有效，以及（2）增强了光吸收以及由于固态分子扩展的端基共轭作用，使得固态包装更加有序。有了这些，以FDNCTF为受主和宽带隙聚合物PBDB-T为施主的太阳能电池表现出11.2％的高功率转换效率（PCE），J _sc增强，维持了高V _oc，与以苯并茚满酮为末端基团的FDICTF装置相比，FF显着提高了72.7％。这些结果表明，端基的未探索的共轭大小对其太阳能电池器件的性能起着至关重要的作用。