聚合物结构和温度对聚合物太阳能电池异质结界面电荷分离态的影响

Polymer solar cells have received a great deal of attention and are developed fast due to their great potential value in practical applications. However, the mechanism for charge separation is not clear and becoming research hot spot. .It is a simple and direct way to study charge separation property by detecting photoluminescence (PL) and electroluminescence (EL) of charge transfer state (CT). In this project, a series of high performance polymers will be used as the donors and the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) will be used as the acceptor. The CT spectra properties of the films and devices of their blends will be investigated under illumination and electric field. The results are expected to indicate the weighted ratio of several electron-hole recombination mechanisms. The influences of the minor polymer chemical structure adjustments, such as the length, angle and type of alkyl-side chains and replacement of heteroatoms of the polymer, on the above-mentioned scientific issues will be revealed. On this basis, the charge separation of CT state will be investigated under extremely low temperature, which can prevent the absorption of extra heat for CT excitons to separate into electron and hole. The experimental results will be explained by the study of the dynamics PL spectra of CT state in combination with the opto-electric numerical calculations. The relationship between PL or EL spectra of CT state and device open-circuit voltage as well as photocurrent under different conditions will be demonstrated..The results of this project will be of importance for further understanding of the charge separation mechanism of CT state in high-performance PSCs and optimization of polymer structures.

聚合物太阳能电池作为一种具有巨大潜在应用价值的技术，近年来受到了广泛关注并发展迅速。而其机理特别是电荷分离过程一直是学术界的研究难点和热点。利用电荷分离态发光光谱研究电荷分离过程是一种简单又直接的方法。本项目将采用一类高性能聚合物作为电子给体，富勒烯衍生物PCBM作为电子受体，研究其共混薄膜和器件在外加光场和电场作用下的电荷分离态发光光谱特性，用于阐明几种电子空穴复合湮灭机制所占的权重比例，揭示聚合物链长、链角、链型及取代原子等细微化学结构调整对上述科学问题的影响。在此基础上，通过低温极端条件抑制CT态激子吸收外界热量进行分离，研究电荷分离态发光光谱动力学过程，并结合光-电数值计算解释实验现象。本项目把不同外界条件下的电荷分离态发光光谱特性同器件开路电压、光生电流等器件参数有机结合起来。通过本项目的研究，对进一步深入了解高性能聚合物太阳能电池电荷分离机理和优化聚合物化学结构具有重要意义。

利用电荷分离态发光光谱研究电荷分离过程是一种简单又直接的方法。项目取得了如下重要结果：（1）首次采用电荷分离态发光光谱和吸收光谱研究了双三元系统聚合物太阳能电池。活性层采用一种给体、两种受体，溶剂采用三种溶剂，有效地提高了太阳能吸收和电荷分离效率。采用光谱测量和傅立叶吸收光谱，测量和计算电荷转移态位置和不同结构对其影响，发现双三元系统对电荷转移态有一定的影响，这与其开路电压变化有密切关系。另外，通过瞬态溶剂蒸发率、AFM、TEM、UPS、EQE等手段系统研究了无铟双三元系统电池，其结果发表在A1区杂志 Journal of Materials Chemistry A 2015, 3: 18365-18371，并以封面论文进行了报道（IF=7.4） 第一单位，通讯作者。（2）采用电荷分离态研究了界面层共混活性层聚合物太阳能电池器件，通过调节表面能能，通过分子之间相互作用力，实现了一步法制备聚合物太阳能电池。发现电子界面材料掺杂活性材料并不影响点和转移态特性，并用开尔文、阻抗和光学矩阵计算和AFM研究了其区别及掺杂浓度影响，其结果对简化大面积制备聚合物太阳能电池有重要的作用，工作发表在A1区杂志Journal of Materials Chemistry A 2015, 3: 20500-20507.（IF=7.4）第一单位，通讯作者。（3）对聚合物给体、寡聚物给体、蓝光空穴界面材料、活性层制备方法、新型光伏结构等进行了研究。关于对金字塔结构的聚合物太阳能电池Pyramid shape of polymer solar cells: a simple solution to triple efficiency，J Phys D: Appl Phys 2013, 46: 305101 (IF=2.5)被英国物理协会评为2013年研究亮点，颁发证书，并被美国物理学会网站进行了详细报道（http://physicsbuzz.physicscentral.com）；关于量子点光伏器件和蓝光发光器件也被作为封面论文报道，刮膜光伏论文被评为2015年ESI高被引论文（三篇论文本人都为通讯作者）。（4）8个中国发明专利授权，5个实用新型专利授权，研制的聚合物光伏制备设备对该方向发展特别具有现实意义。