Morphology-performance relationships in polymer/fullerene blends probed by complementary characterisation techniques - effects of nanowire formation and subsequent thermal annealing
Morphology-performance relationships in polymer/fullerene blends probed by complementary characterisation techniques - effects of nanowire formation and subsequent thermal annealing
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DOI：
10.1039/c5tc01720c
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发表时间：
2015-01-01
影响因子：
6.4
通讯作者：
Kim, Ji-Seon
中科院分区：
文献类型：
--
作者：
Kim, Jong Soo;Wood, Sebastian;Kim, Ji-Seon
我们报告详细分析的薄膜形态（分子堆积，分子构象顺序，和垂直相分离）的性能（电荷传输，光电流产生，和光伏性能）的关系下纳米线的形成和随后的热退火聚合物：富勒烯共混物。聚（3-己基噻吩）（P3 HT）的纳米线通过从溶液中控制沉淀形成，并与[6，6]-苯基-C-61-丁酸甲酯（PCBM）共混以形成本体异质结薄膜。纳米线的形成和进一步的热退火导致P3 HT的分子有序性增加，其中短程构象有序性通过在100 ℃下退火而最大化，并且当在更高温度下退火时降低，但是长程分子堆积的质量和层状堆积距离随着退火温度高达150 ℃而增加。长程有序与空穴迁移率的增加密切相关，但短程构象有序的减少表明在这种聚集的聚合物形态中共轭主链的平面性略有降低。光电导原子力显微镜揭示了增强的连接性的空穴传输纳米线网络作为热退火的结果。此外，我们发现，纳米线形态的结果在一个有利的垂直相分离，与PCBM富集在电子提取表面在传统的架构，这是相反的非纳米线的情况下。这种效果进一步鼓励热退火，导致开路电压的增强，并代表了传统的P3 HT：PCBM器件的形态优势。我们的研究确定了一个重要的长程和短程分子之间的相互作用，在电荷产生，传输，提取，因此太阳能电池器件的性能。
We report detailed analysis of the thin film morphology (molecular packing, molecular conformational order, and vertical phase separation) - performance (charge transport, photocurrent generation, and photovoltaic performance) relationships under nanowire formation and subsequent thermal annealing in polymer: fullerene blends. Nanowires of poly(3-hexylthiophene) (P3HT) are formed by controlled precipitation from solution and blended with [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) to form bulk heterojunction thin films. The formation of nanowires and further thermal annealing result in increased molecular order of the P3HT, where the short-range conformational order is maximised by annealing at 100 degrees C and decreases when annealed at higher temperatures, but the quality of long-range molecular packing and lamellar packing distance increase with annealing temperature up to 150 degrees C. The long-range order correlates strongly with an increase in hole mobility, but the reduction in short-range conformational order indicates a slight reduction in planarity of the conjugated backbone in this aggregated polymer morphology. Photoconductive atomic force microscopy reveals enhanced connectivity of the hole transporting nanowire network as a result of thermal annealing. Additionally, we find that the nanowire morphology results in a favourable vertical phase separation, with PCBM enrichment at the electron-extracting surface in the conventional architecture, which is contrary to the non-nanowire case. This effect is further encouraged by thermal annealing, resulting in an enhancement of open-circuit voltage, and represents a morphological advantage over conventional P3HT: PCBM devices. Our study identifies an important interplay between long-range and short-range molecular order in charge generation, transport, extraction, and hence solar cell device performance.