Hierarchical Nanomorphologies Promote Exciton Dissociation in Polymer/Fullerene Bulk Heterojunction Solar Cells
Hierarchical Nanomorphologies Promote Exciton Dissociation in Polymer/Fullerene Bulk Heterojunction Solar Cells
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DOI：
10.1021/nl201715q
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发表时间：
2011-09-01
期刊：
影响因子：
10.8
通讯作者：
Darling, Seth B.
中科院分区：
文献类型：
--
作者：
Chen, Wei;Xu, Tao;Darling, Seth B.
在聚合物/富勒烯体相异质结太阳能电池中，由硫代[3，4-b]噻吩基和苯并二噻吩基交替重复单元组成的PTB7半导体共聚物创造了太阳能转换效率(7.4%)的历史纪录。为了进一步提高太阳能电池的性能，彻底了解与PTB7/富勒烯和相关的有机光伏(OPV)器件相关的结构-性质关系是至关重要的。传统上，OPV有源层被视为具有离散界面的纯聚合物和富勒烯的相互渗透网络。在这里，我们展示了PTB7/富勒烯OPV器件的活动层实际上包括从几个纳米的微晶到富PTB7和富富勒烯的区域中的几十纳米的纳米晶体聚集体的分级纳米形态，这些纳米聚集体本身的尺寸为数百纳米。这些层次化的纳米形态与显著增强的激子解离相耦合，从而导致光电流，这表明在多个长度尺度上的纳米结构特征是决定PTB7共聚物以及可能大多数聚合物/富勒烯体系在OPV器件中性能的关键因素之一。
PTB7 semiconducting copolymer comprising thieno[3,4-b]thiophene and benzodithiophene alternating repeat units set a historic record of solar energy conversion efficiency (7.4%) in polymer/fullerene bulk heterojunction solar cells. To further improve solar cell performance, a thorough understanding of structure-property relationships associated with PTB7/fullerene and related organic photovoltaic (OPV) devices is crucial. Traditionally, OPV active layers are viewed as an interpenetrating network of pure polymers and fullerenes with discrete interfaces. Here we show that the active layer of PTB7/fullerene OPV devices in fact involves hierarchical nanomorphologies ranging from several nanometers of crystallites to tens of nanometers of nanocrystallite aggregates in PTB7-rich and fullerene-rich domains, themselves hundreds of nanometers in size. These hierarchical nanomorphologies are coupled to significantly enhanced exciton dissociation, which consequently contribute to photocurrent, indicating that the nanostructural characteristics at multiple length scales is one of the key factors determining the performance of PTB7 copolymer, and likely most polymer/fullerene systems, in OPV devices.