基于噻吩类有机胺分子结构设计可控构筑二维/三维钙钛矿异质结的研究

The hybrid dimensional heterojunction formed by the combination of two-dimensional (2D) and three-dimensional (3D) perovskite is expected to solve the instability problem of perovskite solar cells. However, it is still difficult to realize the dual enhancement of the efficiency and stability of perovskite devices by using the heterojunction. At present, the 2D perovskite in bulk and bilayer heterojunctions obtained by random self-assembly technique is mostly mixed layer number, and moreover the structure choices of organic amine are very little. Those make many difficulties for bringing the morphology and carrier transport of mixed dimensional perovskite films under effective control. This project intends to use the structural design of organic amines to achieve precise control over the properties of 2D/3D heterojunction interfaces. We will firstly select thiophene-based amines to prepare 2D perovskite single crystals. By adjusting the conjugate length and substituent group of thiophene molecule, the crystallization and band structure of the corresponding 2D perovskite can be controlled, and next the bulk and bilayer heterojunction will be prepared by the combination of our 2D perovskite. Then, the effect of 2D perovskite on the crystal orientation and charge transfer of mixed perovskite will be thoroughly analyzed. In this light, we can grasp the principle of how the molecular structures of organic amines regulate the interface structures and electrical properties of heterojunction. Finally, a hybrid heterojunction structure based on the combination of bulk and bilayer heterojunction will be designed for the fabrication of high efficient and stable perovskite solar cells.

通过二维与三维钙钛矿结合形成混合维度异质结有望解决钙钛矿太阳能电池的不稳定性问题，然而利用异质结实现钙钛矿器件效率和稳定性的双提升仍然困难重重，目前随机自组装技术获得的体相和双层异质结中二维钙钛矿多为混合层数，且有机胺分子结构单一，这限制了其对混合维度钙钛矿薄膜形貌及载流子输运的有效调控。本项目拟利用有机胺分子的结构设计实现对二维/三维异质结界面性质的精确控制：将首先选用噻吩类有机胺制备二维钙钛矿单晶，通过调节噻吩分子的共轭长度和取代基团，控制相应二维钙钛矿的结晶性和能带结构，然后结合三维钙钛矿分别制备体相与双层异质结；再详尽剖析二维钙钛矿对混合维度钙钛矿结晶取向和电荷转移的影响，据此掌握有机胺的分子结构调控异质结界面结构和电学性质的机制，进而实现对二维/三维钙钛矿异质结的可控构筑；最终结合体相与双层异质结设计混合异质结器件结构，应用于制备高效且稳定的钙钛矿太阳能电池。

二维钙钛矿材料具有丰富结构和良好的化学稳定性，二维和三维钙钛矿的组合能同时提高器件的光电转换效率和稳定性而引起了广泛的关注；然而，其复杂的异质结界面结构，限制了钙钛矿异质结对薄膜形貌及载流子输运的有效调控。我们首先选择共轭结构（如噻吩类）有机胺分子，通过其共轭链长短和电子云密度有效调控二维钙钛矿晶体的堆叠结构以及能带结构，然后建立了有机胺分子结构与二维钙钛矿材料性能的内在联系。我们然后开发了预结晶方案制备钙钛矿薄膜，实现了对二维/三维钙钛矿体相与双层异质结的可控构筑，并在此基础上研究有机胺的分子结构变化对界面微观结构和能带结构的影响，据此，我们掌握了两者之间的关联模型。材料分子结构的研究结果表明，在二维钙钛矿材料中采用噻吩类有机胺，可提高材料的电导率和结晶性能，在无甲胺的三位钙钛矿中采用协同作用下的组分调控方案，可实现对不同类型缺陷形成能的精准调控。钙钛矿薄膜制备的研究结果表明，采用预结晶方案可有效改善二维钙钛矿相的纯度，对比在三维钙钛矿前驱体溶液中添加不同分子结构类型的二维钙钛矿，揭示了在二维钙钛矿中选用与三维钙钛矿晶格常数失配的分子结构和离子运动稳定性高的共轭有机配体，可避免阳离子和卤素离子的之间的扩散和化学键断裂，进而确保二维钙钛矿的相纯度。钙钛矿异质结器件性能的研究结果表明，前后端界面合理搭配双层异质结，可实现电荷的高效传输和收集；在晶界处合理搭配的体相异质结，是钝化缺陷和抑制离子扩散的有效策略。最终，实现了钙钛矿器件效率和稳定性的双提升，在1cm2的尺寸上获得22%光电转换效率的单结钙钛矿电池，获得了超过28%光电转换效率的叠层电池，并在加速老化实验中持续光照1,000h，未封装器件性能衰减不超过10%。这些研究成果对推动钙钛矿光伏技术应用具有一定的价值。项目按计划顺利完成，达到了预期结果，实施过程中以通讯作者共发表SCI论文12篇，发明专利授权2项，申请4项。