基于三元体系厚活性层有机光伏器件的研究

Incomplete light absorption of the active-layer acts as a bottleneck for further improving device performance of bulk heterojunction (BHJ) organic solar cell. In this project, we propose ternary-based thick organic solar cells with aim to strongly enhance light absorption while accompanying with an inhibited electron-hole recombination by introducing a high-mobility conjugated polymer, which combine to result in highly efficient power conversion efficiency and long-term stability. The thickness, light utilizing and charge transport in such thick active-layer are systematically investigated. The insight will enable us identify the relationship of light utilizing-charge transport, and the control strategies for the optimal BHJ active layer. The analysis of kinetics during solution-processing, including film formation, crystallization and phase separation, provides us insight that how dynamics influence the location of components, domain size, impurity of phase and molecular aggregation. This will help construction of the optimal BHJ structure for the charge dissociation and transport in the active layer. The synergetic effect of light utilizing-charge transport and BHJ characteristics on device performance will be investigated. The underlying operating mechanism of ternary-based thick organic solar cells provides us insights and guidelines to construct highly efficient ternary-based organic solar cells with long-term stability.

针对本体异质结有机光伏器件活性层光子利用率低的核心问题，本项目提出基于三元体系的厚活性层方案，提高活性层的光子利用率并利用第三元聚合物高空穴迁移率抑制活性层内电子-空穴复合，实现有机光伏器件光电转化率和器件寿命的提高。通过研究活性层厚度、光子利用率和电荷传输，建立光子利用-电荷传输平衡关系和基于三元体系厚活性层的最佳设计方案；通过研究溶液成膜过程的成膜、结晶和相分离动力学以及本体异质结性质，阐明动力学与本体异质结中各相分布、相区尺寸、相内纯度和分子有序堆积的内在联系，实现最优化电荷分离和电荷传输所需本体异质结的构建；研究光子利用-电荷传输关系与本体异质结性质对光伏器件性能的协同性作用，揭示基于三元体系厚活性层有机光伏器件的工作原理，为制备基于三元体系的高效率高寿命有机光伏器件提供理论依据和技术支持。

有机半导体分子作为太阳电池的活性层，其光电性质严重依赖于薄膜的成膜、结晶和相分离动力学以及本体异质结性质。针对上述关键科学问题，本项目通过高能同步辐射X-射线散射原位追踪半导体成膜过程的结晶过程，并通过薄膜后处理调控结晶和相分离顺序，从而构建出高结晶、低缺陷、高电荷传输的太阳电池活性层。ITIC/PBDB-T体系成膜结晶动力学分析结果表明，当ITIC分子先于PBDB-T分子结晶时，ITIC具有高的分子迁移能力，ITIC/PBDB-T倾向于形成高结晶性互穿网络结构，提高了太阳电池电流传输并抑制了双分子电荷复合；当PBDB-T分子先结晶时，ITIC结晶能力被抑制，ITIC/PBDB-T体系无法构建有效的电荷传输通道。ITIC/钙钛矿体系成膜结晶动力学分析结果表明，当ITIC在旋涂钙钛矿溶液时候引入，可诱导钙钛矿溶剂化晶相垂直方向取向，在热退火时候，ITIC与钙钛矿形成路易斯酸碱相互作用，有效降低太阳电池活性层晶区缺陷和器件寿命。该项目建立了有机半导体的成膜结晶和相分离对薄膜光电性质和器件性能的影响规律，为构建高效和高稳定太阳电池提供了理论依据和技术支持。