In this paper, we designed and synthesized six new wide band gap donor-acceptor (D-A) copolymers, PZ2-PZ7, with diazine isomers (pyrazine, pyridazine, pyrimidine) as the A unit and alkylthiophene- or alkylthiothienyl-substituted BDT as the D unit. The effect of diazine isomeric A units and side-chain substituents on molecular structure, optoelectronic properties and photovoltaic performances of the resulting D-A copolymers were investigated in details. Six low-cost polymers were easily obtained by minimal reaction steps and cheap raw materials. All the polymers exhibited wide band gaps (WBGs) (>1.9 eV) and deep-lying HOMO energy levels (<−5.48 eV), which is convenient for paring with low band gap nonfullerene acceptors (NFAs). Theoretical simulation calculation indicates that diazine isomeric A unit has great impact on the planarity of polymer backbone. Bulk heterojunction polymer solar cells (PSCs) were fabricated with these polymers as donor materials and representative NFAs (Y6 and ITIC) as acceptor materials. After optimization, pyrazine-based polymers PZ2 and PZ3 exhibited higher PCEs than those of pyridazine- and pyrimidine-based ones (PZ4-PZ7) regardless of the acceptors. Finally, the PZ2:Y6-based PSC achieved the highest power conversion efficiency (PCE) up to 11.21 %, which could be attributed to more balanced carrier mobility, increased charge dissociation probability, reduced charge recombination, and superior active layer morphology. This work suggests that diazine-based WBG polymers, especially for pyrazine, would become as very promising donor candidates for constructing low-cost and efficient NFA-based PSCs.

在本文中，我们设计并合成了六种新型宽带隙给体-受体（DA）共聚物PZ2 - PZ7 ，其以二嗪异构体（吡嗪、哒嗪、嘧啶）为A单元，以烷基噻吩或烷基噻吩基取代的BDT为D单元单元。详细研究了二嗪异构体A单元和侧链取代基对所得DA共聚物的分子结构、光电性能和光伏性能的影响。通过最少的反应步骤和廉价的原材料可以轻松获得六种低成本聚合物。所有聚合物均表现出宽带隙（WBG）（>1.9 eV）和深层HOMO能级（<−5.48 eV），这很容易与低带隙非富勒烯受体（NFA）配对。理论模拟计算表明，二嗪异构体A单元对聚合物主链的平面度影响很大。使用这些聚合物作为供体材料和代表性 NFA（Y6 和 ITIC）作为受体材料制造了体异质结聚合物太阳能电池（PSC）。优化后，无论受体如何，吡嗪基聚合物PZ2和PZ3都表现出比哒嗪基和嘧啶基聚合物(PZ4 - PZ7)更高的 PCE。最后，基于PZ2 :Y6的PSC实现了高达11.21%的最高功率转换效率（PCE），这可归因于更平衡的载流子迁移率、增加的电荷解离概率、减少的电荷复合和优异的有源层形态。这项工作表明，基于二嗪的 WBG 聚合物，尤其是吡嗪，将成为构建低成本、高效的基于 NFA 的 PSC 的非常有前途的供体候选者。