Dramatic performance enhancement for large bandgap thick-film polymer solar cells introduced by a difluorinated donor unit
Dramatic performance enhancement for large bandgap thick-film polymer solar cells introduced by a difluorinated donor unit
复制标题
DOI：
10.1016/j.nanoen.2015.05.016
复制
发表时间：
2015-07-01
期刊：
影响因子：
17.6
通讯作者：
Yan, He
中科院分区：
文献类型：
--
作者：
Li, Zhengke;Lin, Haoran;Yan, He
我们报道了一种大带隙（1.9 eV）供体-受体共聚物（命名为PffT2-FTAZ），该共聚物使聚合物太阳能电池具有7.8%的高功率转换效率。PffT2-FTAZ聚合物的一个重要结构特征是二氟化给体单元（3,3-二氟-2,2-二噻吩，或ffT2），它带来了一些令人惊讶和/或有益的效果。通过比较PffT2-FTAZ与在双噻吩给体单元上没有氟化的类似聚合物（PT2-FTAZ），发现ffT2单元有效地降低了聚合物的HOMO和LUMO能级，并略微减小了光学带隙。它还为溶液中的聚合物引入了强的链间聚集，从而导致高度结晶的聚合物膜和合理的高空穴迁移率。另一方面，PffT2-FTAZ：富勒烯共混物仍然具有相当小的聚合物畴尺寸，适合于聚合物太阳能电池的运行。所有这些积极因素的结合导致聚合物太阳能电池的性能显著提高，功率转换效率从PT2-FTAZ的2.8%提高到f PffT2-FTAZ的7.8%。PffT2-FTAZ的高PSC性能使其成为高效串联PSC的理想候选材料。(C) 2015 Elsevier Ltd.版权所有。
We report a large bandgap (1.9 eV) donor-acceptor copolymer (named PffT2-FTAZ) that enables polymer solar cells with a high power conversion efficiency of 7.8%. An important structural feature of the PffT2-FTAZ polymer is a difluorinated donor unit (3,3-difluoro-2,2-bithiophene, or, ffT2) that introduces several surprising and/or beneficial effects. By comparing PffT2-FTAZ with the analog polymer (PT2-FTAZ) without fluorination on the bithiophene donor unit, it is found that the ffT2 unit effectively lowers the HOMO and LUMO energy levels of the polymer and slightly reduces optical bandgap. It also introduces strong interchain aggregation for the polymer in solution, which leads to a highly crystalline polymer film and reasonably high hole transport mobility. On the other hand, the PffT2-FTAZ: fullerene blend still exhibits a reasonably small polymer domain size suitable for polymer solar cell operation. All these positive factors combined leads to dramatically enhanced performance for the polymer solar cells with the power conversion efficiency increasing from 2.8% for PT2-FTAZ to 7.8% for f PffT2-FTAZ. The high PSC performance of PffT2-FTAZ makes it a promising candidate for high efficiency tandem PSCs. (C) 2015 Elsevier Ltd. All rights reserved.