Insight into correlation between molecular length and exciton dissociation, charge transport and recombination in Polymer: Oligomer based solar cells
Insight into correlation between molecular length and exciton dissociation, charge transport and recombination in Polymer: Oligomer based solar cells
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深入了解聚合物：基于低聚物的太阳能电池中分子长度与激子解离、电荷传输和复合之间的相关性
DOI：
10.1016/j.orgel.2018.04.003
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发表时间：
2018-07-01
影响因子：
3.2
通讯作者：
Xie, Zhiyuan
中科院分区：
文献类型：
--
作者：
Fu, Yingying;Qu, Jianfei;Xie, Zhiyuan
选择四种不同重复单元数的芴-二-2-噻吩-苯并噻唑（FTBT）低聚物作为P3HT：低聚体太阳能电池的电子受体。详细研究了低聚物长度对相分离行为的影响。结果表明，低聚物长度强烈影响薄膜形态，从而影响激子解离概率、电荷输运以及复合特性。短聚物F1TBT1容易聚集并形成大规模相分离，阻碍了共混膜中的激子解离。随着受体长度的增加，由于长FTBT低聚物在聚合物基体中的迁移能力减弱，大规模聚集逐渐受到抑制。同时，随着低聚物长度的延长，电子迁移率提高，有利于抑制共混物中的电荷复合。最后，基于P3HT:F3TBT3的太阳能电池实现了最佳的光电性能，PCE为4.19%，在有效的激子解离和平衡的电荷传输之间取得了很好的平衡，几乎是基于F1TBT1的器件的三倍。这项工作强调，裁剪低聚物长度可以作为一种有效的策略来控制相分离，提高非富勒烯基聚合物太阳能电池的光伏性能。
Four fluorene-alt-di-2-thienyl-benzothiadiazole (FTBT) based oligomers with different number of repeated units are selected as electron acceptors in P3HT:oligomer solar cells. The effect of oligomer length on the phase separation behavior has been studied in detail. It is disclosed that the oligomer length strongly affects the film morphology and hence the exciton dissociation probability, charge transport as well as recombination characteristics. The short oligomer F1TBT1 is prone to aggregate and form large-scale phase separation which impedes exciton dissociation in the blend films. With increasing the acceptor length, large-scale aggregations are gradually suppressed due to the weakened migration ability of long FTBT oligomers in polymer matrix. Meanwhile, electron mobilities are enhanced with extending the oligomer length, which is favorable to suppress charge recombination in the blends. Finally, optimal photovoltaic performances with a PCE of 4.19% are achieved in P3HT:F3TBT3 based solar cell that compromises well between efficient exciton dissociation and balanced charge transport, which is almost three times higher than the F1TBT1 based device. This work highlights that tailoring the oligomer length can be used as an effective strategy to control phase separation and to enhance the photovoltaic performance in non-fullerene based polymer solar cells.