Elongated Nanodomains and Molecular Intermixing Induced Doping in Organic Photovoltaic Active Layers with Electric Field Treatment
Elongated Nanodomains and Molecular Intermixing Induced Doping in Organic Photovoltaic Active Layers with Electric Field Treatment
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DOI：
10.1021/acsapm.9b00833
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发表时间：
2019-08
影响因子：
5
通讯作者：
Rabindra Dulal;Akshay Iyer;Umar Farooq Ghumman;Joydeep Munshi;Aaron Wang;G. Balasubramanian;Wei Chen;T. Chien
中科院分区：
文献类型：
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作者：
Rabindra Dulal;Akshay Iyer;Umar Farooq Ghumman;Joydeep Munshi;Aaron Wang;G. Balasubramanian;Wei Chen;T. Chien
研究了电场辅助退火对有机光伏电池P3 HT/PCBM有源层中异质结纳米形貌的影响。人们普遍认为，电场辅助退火将促进极性聚合物P3 HT更好地结晶，以提高电荷迁移率，从而改善OPVC的性能。电子给体畴和电子受体畴对纳米形貌的影响还没有很好的理解。在这里，使用横截面扫描隧道显微镜和光谱（XSTM/S），电场辅助退火处理被发现影响的分子域被拉长的方向附近的外部电场。分子域的伸长被认为有助于域渗透，这导致更高的电荷迁移率，因此更高的短路电流密度（Jsc）。另一方面，还观察到电场辅助退火样品中富含P3 HT和富含PCBM的畴的电子性质显示出两个畴之间较小的能带隙和较小的分子轨道偏移，这被认为会降低开路电压（Voc）并对OPVC性能产生负面影响。基于X射线衍射（XRD）和小角X射线散射（SAXS）的结果，电子性质的改变被认为是由于分子混合诱导的掺杂效应。这些结果指出了影响电场辅助退火处理的OPVC性能的竞争因素。
The effects of the electric-field-assisted annealing on the bulk heterojunction nano-morphology in the P3HT/PCBM active layer of the organic photovoltaic cells (OPVCs) are presented here. It was widely accepted that the electric-field-assisted annealing will facilitate the P3HT, the polar polymer, to be better crystalline to enhance the charge mobility, hence the improvement of the OPVC performance. The influences on the nano-morphology of the electron donor and accepter domains are not well understood. Here, using the cross-sectional scanning tunneling microscopy and spectroscopy (XSTM/S), the electric-field-assisted annealing treatment is found to influence the molecular domains to be elongated with the orientation near the direction of the external electric field. The elongation of the molecular domains is believed to facilitate the domain percolation, which causes higher charge mobility, hence the higher short-circuit current density (Jsc). On the other hand, it was also observed that the electronic properties of the P3HT-rich and PCBM-rich domains in the electric-field-assisted annealed samples showed smaller energy band gaps and smaller molecular orbital offset between the two domains, which is argued to decrease the open circuit voltage (Voc) and negatively impact the OPVC performance. Based on the X-ray diffraction (XRD) and small angle X-ray scattering (SAXS) results, the altered electronic properties are argued to be due to the molecular intermixing induced doping effects. These results point out competing factors affecting the OPVC performance with the electric-field-assisted annealing treatment.