Two new wide-bandgap polythiophenes, i.e., poly[5,5′-bis(2-hexyldecyl)-(2,2′-bithiophene)-4,4′-dicarboxylate-alt-5,5′-3-chloro-2,2′-bithiophene] (PDCBT-Cl) and poly[5,5′-bis(2-hexyldecyl)-(2,2′-bithiophene)-4,4′-dicarboxylate-alt-5,5′-3,3′-dichloro-2,2′-bithiophene] (PDCBT-2Cl) comprising 3-chloro-2,2′-bithiophene and 3,3′-dichloro-2,2′-bithiophene moieties, respectively, were synthesized for fullerene-free polymer solar cells (PSCs). For comparison, three other polymers based on [2,2′-bithiophene]-4,4′-dicarboxylate (DCBT), i.e., PDCBT, PDCBT-F, and PDCBT-2F with 2,2′-bithiophene, 3-fluoro-2,2′-bithiophene, and 3,3′-difluoro-2,2′-bithiophene as comonomers, respectively, were also prepared. PSC devices were fabricated with these polymers as donor materials and ITIC-Th1 as acceptor. The incorporation of chlorine (Cl) or fluorine (F) atoms into polymers both efficiently downshifted the highest occupied molecular orbital (HOMO) energy levels, leading to higher open-circuit voltage (V_oc) in the PSCs. Owing to the proper phase-separated morphology with favorable molecular packing and miscibility, the device based on PDCBT-Cl:ITIC-Th1 exhibited efficient exciton dissociation and charge collection as well as weak charge recombination and thereby displayed the best power conversion efficiency (PCE) up to 12.38%. The devices based on other polymers showed inferior PCEs (8.14% for PDCBT, 10.85% for PDCBT-F, 8.48% for PDCBT-2F, and 6.94% for PDCBT-2Cl). The monomers that are used to make PDCBT-Cl can be synthesized in relatively large scale from commercial available chemicals. All these indicate that PDCBT-Cl is a promising donor material for the large area fabrication of high-performance fullerene-free PSCs.

中文翻译：

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高效无富勒烯聚合物太阳能电池的羧酸取代聚噻吩：氯化对其性能的影响

两个新的宽带隙聚噻吩，即，聚[5,5'-双（2-己基癸） - （2,2'-联噻吩）-4,4'-二羧酸酯ALT -5,5'- -3-氯2,2'-联噻吩]（PDCBT-C1）和聚[5,5'-双（2-己基癸） - （2,2'-联噻吩）-4,4'-二羧酸酯中高音-5,5'-3,3'-dichloro-2,2'-bithiophene]（PDCBT-2Cl）包含3-chloro-2,2'-bithiophene和3,3'-dichloro-2,2'-bithiophene分别合成了不含富勒烯的聚合物太阳能电池（PSC）的部分。为了比较，基于[2,2'-联噻吩] -4,4'-二羧酸酯（DCBT）的其他三种聚合物，即PDCBT，PDCBT-F和PDCBT-2F与2,2'-联噻吩，3-氟还分别制备了作为共聚单体的-2，2′-联噻吩和3，3′-二氟-2，2′-联噻吩。使用这些聚合物作为供体材料并使用ITIC-Th1作为受体来制造PSC器件。将氯（Cl）或氟（F）原子结合到聚合物中均有效地降低了最高占据分子轨道（HOMO）的能级，从而导致更高的开路电压（V _oc）。由于具有良好的分子堆积和可混溶性的适当的相分离形态，基于PDCBT-Cl：ITIC-Th1的器件显示出有效的激子离解和电荷收集以及弱的电荷重组，因此显示出最佳的功率转换效率（PCE）高达12.38％。基于其他聚合物的设备显示出较差的PCE（PDCBT为8.14％，PDCBT-F为10.85％，PDCBT-2F为8.48％，PDCBT-2Cl为6.94％）。用于制备PDCBT-Cl的单体可以从市售化学品中以相对较大的比例合成。所有这些表明，PDCBT-Cl是大面积制造高性能无富勒烯PSC的有前途的供体材料。