With their rapid development in recent years, organic solar cells hold the exciting potential to be a groundbreaking form of solar harvesting technology. Among these, all-polymer solar cells (all-PSCs) stand out owing to various advantages such as complementary absorption and superior stability. However, the advance of all-PSCs has been greatly impeded by energy level mismatches and unfavorable morphology of the active layer. Here, we report a molecular engineering approach featuring asymmetrical 4-methoxythiophene/thiophene as conjugated side chains of the donor polymer to fine-tune the energy level alignment and phase separation. The corresponding polymer, namely, poly{4-[5-(2-ethylhexyl)-4-methoxythiophen-2-yl]-8-[5-(2-ethylhexyl)thiophen-2-yl]benzo[1,2-b:4,5-b′]dithiophene}-alt-[bis(5-thiophene-2-yl)-5,6-difluoro-2-(2-hexyldecyl)-2H-benzo[d][1,2,3]triazole-4,7-diyl] (PMOT32) exhibited a power conversion efficiency that exceeded 8.5% in all-PSCs with poly{[N,N′-bis(2-octyldodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (N2200) as the acceptor. PMOT32:N2200 also maintained good photovoltaic performance when processed as a thick film or from non-halogenated solvents. Detailed comparisons with two other polymers with pure thiophene or 4-methoxythiophene as their side chains revealed how these side chains affected the photovoltaic performance via energy level alignment and phase separation.

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高性能全聚合物太阳能电池共轭侧链的合理设计

随着近几年的快速发展，有机太阳能电池具有令人激动的潜力，成为太阳能收集技术的开创性形式。其中，全聚合物太阳能电池（all-PSC）由于具有多种优势（例如互补吸收和出色的稳定性）而脱颖而出。然而，全PSC的发展已受到能级失配和活性层形态不利的严重阻碍。在这里，我们报告了一种分子工程方法，其特征在于不对称的4-甲氧基噻吩/噻吩作为供体聚合物的共轭侧链，以微调能级排列和相分离。相应的聚合物，即聚{4- [5-（2-乙基己基）-4-甲氧基噻吩-2-基] -8- [5-（2-乙基己基）噻吩-2-基]苯并[1,2- b：4,5- b′]二噻吩} -alt- [双（5-噻吩-2-基）-5,6-二氟-2-（2-己基癸基）-2 H-苯并[ d ] [1,2,3]三唑-4 ，7-二基]（PMOT32）在具有聚{[ N，N'-双（2-辛基十二烷基）-1,4,5,8-萘二甲酰亚胺-2,6]的全PSC中表现出超过8.5％的功率转换效率-二基] -alt-5,5'-（2,2'-联噻吩）}（N2200）作为受体。当制成厚膜或使用非卤代溶剂加工时，PMOT32：N2200还保持了良好的光伏性能。与另外两种具有纯噻吩或4-甲氧基噻吩作为侧链的聚合物的详细比较显示，这些侧链如何通过能级对准和相分离影响光伏性能。