A series of new dinuclear copper complexes with a tetraphosphane bridging ligand, [{(pz 4 B)Cu} 2 (μ-tpbz)] (1), [{(pz 2 BH 2 )Cu} 2 (μ-tpbz)] (2), and [{(tz 2 BH 2 )Cu} 2 (μ-tpbz)] (3) [tpbz = 1,2,4,5-tetrakis(diphenylphosphanyl)benzene, pz 4 B = tetrakis(pyrazol-1-yl)borate, pz 2 BH 2 = bis(pyrazol-1-yl)borohydrate, and tz 2 BH 2 = bis(1,2,4-triazol-1-yl)borohydrate], have been synthesized and structurally characterized. The Cu I atoms in these complexes are four-coordinate and adopt a tetrahedral coordination geometry. In each complex, the copper centers are bridged by a tpbz ligand and each Cu I is further terminally chelated by a borate diimine anion. The central phenylene ring and the phosphine atoms of the tpbz ligand are essentially planar. The two Cu I atoms in each molecule are located above

Nonfullerene acceptors (MQ3, MQ5, MQ6) are synthesized using asymmetric and symmetric ladder‐type heteroheptacene cores with selenophene heterocycles. Although MQ3 and MQ5 are constructed with the same number of selenophene heterocycles, the heteroheptacene core of MQ5 is end‐capped with selenophene rings while that of MQ3 is flanked with thiophene rings. With the enhanced noncovalent interaction of O⋅⋅⋅Se compared to that of O⋅⋅⋅S, MQ5 shows a bathochromically shifted absorption band and greatly improved carrier transport, leading to a higher power conversion efficiency (PCE) of 15.64 % compared to MQ3, which shows a PCE of 13.51 %. Based on the asymmetric heteroheptacene core, MQ6 shows an improved carrier transport induced by the reduced π–π stacking distance, related with the increased dipole moment in comparison with the nonfullerene acceptors based on symmetric cores. MQ6 exhibits a PCE of 16.39 % with a VOC of 0.88 V, a FF of 75.66 %, and a JSC of 24.62 mA cm−2.

Controlling the aggregation of small‐molecule acceptors (SMAs) is essential to obtain an optimal morphology and to improve the photovoltaic performance of polymer solar cells (PSCs). However, reducing intermolecular aggregation of SMAs is usually accompanied by the disruption of compact molecular packing thereby leading to their decreased electron mobilities. Here, two novel M‐series SMAs (MD1T and MD2T) based on ladder‐type heterononacenes with neighboring side‐chains separated by one or two thiophene rings are designed and synthesized. It is found that shortening the spacing of the neighboring side‐chains of the SMAs can greatly alleviate the intermolecular aggregation and alter the molecular orientation from bimodal edge‐on/face‐on to predominant face‐on while maintaining the compact molecular packing. As a result, a more favorable morphology with smaller domain sizes is formed for the MD1T‐based blend films, which greatly improves the charge generation and charge transport for the corresponding PSCs. The best‐performing MD1T‐based device affords an efficiency of 12.43%, over seven times higher than that of the MD2T‐based device. This work reveals the importance of the spacing between the neighboring side‐chains in modulating the molecular aggregation and active layer morphology, and the obtained structure‐performance relationships shall provide important guidance for designing highly efficient SMAs.