二维钙钛矿异质结的可控制备及其电荷输运机制研究

Two-dimensional (2D) Ruddlesden−Popper perovskite solar cells have drawn intensive research attention owing to their superior ambient stability. However, their random crystal distribution and large exciton binding energy suppress charge transport along the vertical direction relative to substrate, leading to severe hysteresis and poor device performance.Therefore, this project intends to construct a new type of Dion-Jacobson 2D perovskite by synthesizing a series of strong electron-negative double-ion organic spacers, which will promote crystal orientation and charge transport. Furthermore, three-dimensional perovskites and MXene with high mobility will be introduced to construct hetero-dimensional and homo-dimensional perovskite heterojunctions, respectively, which will facilitate exciton splitting and improve charge carrier lifetime and diffusion length. Next, by employing time-resolved photoluminescence spectroscopy, transient absorption spectroscopy, terahertz absorption spectroscopy and transient photoconductivity, the charge/energy transfer and charge recombination of 2D perovskites and their heterojunctions will be investigated. Finally, the optimal conditions will be extended to the non-lead 2D perovskites to achieve an effective balance between efficiency, stability and environmentally friendliness. This project provides a novel avenue for the structural, morphological and dimensional control of two-dimensional perovskites, holding huge potential for commercialization.

二维钙钛矿材料由于其优异的稳定性引起了广泛关注。然而其在垂直衬底方向上结晶排列无序，且激子结合能大，导致了电荷输运困难和较低的光电转换效率。因而本项目拟通过设计合成一系列强电负性的双离子型有机间隔层，构建新型Dion-Jacobson类二维钙钛矿体系，以期实现有序取向和促进电荷输运。进一步，引入高迁移率的三维钙钛矿和MXene，分别构筑异维和同维二维钙钛矿异质结，促进激子拆分并提高载流子寿命和扩散长度。结合时间分辨光致发光谱、瞬态吸收谱、太赫兹吸收光谱和瞬态光电导等手段，探明有机间隔层、异质结结构对二维钙钛矿的电荷/能量转移、缺陷态复合等光动力学的影响机制，从而作为实验优化的指导依据。最后，将最优条件应用于非铅类二维钙钛矿体系，实现二维钙钛矿太阳能电池中效率、稳定性和环保性三者之间的有效平衡。本项目为二维钙钛矿的结构、形貌与维度调控提供了新的思路，有利于实现商业化。

二维钙钛矿材料由于其优异的稳定性引起了广泛关注。然而其在垂直衬底方向上结晶排列无序，且激子结合能大，导致了电荷输运困难和较低的光电转换效率。因此，本项目首先利用KSCN添加剂有效调控了钙钛矿的晶型结构，改善了载流子寿命；其次通过添加剂和溶剂的协同作用，实现二维钙钛矿(PEA)2MA3Pb4I13异质结结构的可控制备，且揭示了二维相、三维相在内部电荷输运过程中的不同机制；紧接着，在二维钙钛矿内部引入高迁移率的2D MXene相，使其充当电荷输运的中间桥梁，以解决二维钙钛矿的激子结合能大的本征问题，并提高载流子寿命和扩散长度；最后，制备了非铅类二维钙钛矿异质结(n-BA)2(MA)3Sn4I13:MXene，并对其光电性能进行了初步探索。本项目为二维钙钛矿的结构、形貌与维度调控提供了新的思路，有利于实现商业化。