聚合物光伏器件中电荷高效传输通道的构筑与机理研究

Polymer solar cell (PSC) is a hot option to solve the current energy shortage problem, but low power conversion efficiency is one of bottlenecks factor to limit its application. Although the free charge transport characteristics in the PSC device has an important influence on the power conversion efficiency, but the regulation methods of increasing charge transport efficiency from active layer to electrode are finite. The classical material system P3HT:PCBM will be used as research object in this project, taking interface regulation as breakthrough point. By modulating the structure of the donor/acceptor phases and their interface in the active layer, and the interface structure of active layer/electrode. To find an effective way to improve the charge mobility and its efficient transport path. For this purpose, material preparation, structure characterization and performance testing will be utilized to study the correlation between structural changes of PSC device and photoelectric properties. The transport process and mechanism of hole and electron in active layer will be studied by using time resolved spectroscopy technology. Using transient photoconductivity technology to study charge transfer and recombination mechanism at the interface of active layer/electrode. Through the above research work, to reveal the inherent relationship of the structure of the PSC device and efficient charge transfer characteristics. To establish the relationship between microscopic time charge transport behavior and macroscopic device performance. For improving the photoelectric conversion efficiency of PSC devices to provide new strategy.

聚合物光伏电池是解决当前能源短缺问题的热门选项，但光电转换效率偏低是限制其应用的瓶颈因素之一。虽然电池器件中自由电荷的输运特性对光电转换效率具有重要影响，但调控电荷高效传输至电极的手段却很有限。本项目以经典材料体系P3HT:PCBM为研究对象，以界面调控为切入点，通过调控光活性层中给/受体相结构及其界面结构，以及光活性层与电极界面结构，找到提高电荷迁移率、及其快捷传输途径的有效方案。为此，本项目将综合运用材料制备、结构表征和性能测试手段，研究器件内部结构因素与光电性能间的相关性；运用时间分辨光谱技术研究电子和空穴在光活性层中分相传输的过程与机理；运用瞬态光电导技术研究电池器件中活性层/电极界面附近的电荷复合与收集机制。通过上述研究，揭示器件结构与电荷高效传输特性之间的内在联系，确立微观电荷传输行为与宏观器件性能之间的关联，为改善聚合物光伏器件的光电转换效率提供新思路。

项目首先采用电沉积法制备了ZnO，物相与成分表征证实其主要成分为ZnO，形貌呈片状结构，在400~800 nm区间的透光率大于82%。以此ZnO为电子传输层，P3HT:PC61BM体系的效率可达3.6%。电沉积法可大面积制备ZnO，这为大面积有机光伏器件的制备提供了技术支持。采用酸蚀法修饰ZnO后，使P3HT:PC61BM体系的最大效率提升到3.92%。表面粗糙度表明，酸处理的ZnO粗糙度明显大于未处理的ZnO，使得修饰后的电子迁移率较未处理的提高了1.5倍，证实嵌入活性层的ZnO有助于电子由活性层向界面层转移，与课题设想一致。.为提升电荷在活性层中的传输效率，采用“多步溶解法”调控活性层相形貌。为此，以P3HT:PC61BM和PTB7:PC71BM体系为研究对象。通过光学、电学和形貌表征发现光伏材料经多步溶解后，聚合物有序相含量明显提高，且给受体相结构得到优化；超快动力学表明，活性层形貌优化后的电荷产率和传输效率得到有效提高，使两器件效率分别提高了24%和8%。另一方面，为了研究富勒烯对电荷产生和传输影响，研究了P3HT和P3HT:PC61BM体系中电荷的产生。结果表明：PC61BM相可提高激子的解离，提高电荷产率。在低电荷浓度下，PC61BM相利于提高P3HT相中离域电荷的生成，降低局域电荷的浓度。但在高电荷浓度下，它反而促使P3HT相中离域电荷浓度的降低，并向双极化子转变，这对光电流具有重要意义。.由于活性层形貌与前驱液密切相关，研究了分子在溶液与薄膜中的相关性，发现溶液中的聚集态会在薄膜中有所保留，并对相尺度产生影响。DIO可改善薄膜的相尺度，优化给受相界面，使PTB7:PC71BM器件获得7.4%的效率。这是由于合适的相尺度利于激子转换成自由电荷，并利于电子与空穴分相传输。.通过对项目的研究，为高性能有机光伏器件的制备和光电转换过程的理解提供了技术支持和理论依据。