基于B位掺杂的高性能CsPbI3量子点太阳能电池的组分工程

Inorganic perovskite CsPbI3, with excellent photoelectric properties and high stability to external light, heat and electricity, has become the most rapidly developed photovoltaic material. However, the perovskite structure (cubic phase) is unstable at room temperature due to the radius mismatch of cesium, lead and iodine ions, which will further damage the long-term stability of the CsPbI3 film. To overcome the problem of phase transition and difficulty of B cation doping in CsPbI3 thin film, the partial substitution of Pb ions by smaller divalent B-site cation in CsPbI3 quantum dots will be used to stabilize the cubic phase and realize the long-term stability and high efficiency of CsPbI3 quantum dot solar cells. Meanwhile, the in-situ transmission electron microscopy (TEM) is also used to study the phase transition during B-site doped CsPbI3 quantum dots, to further understand the structural reorganization in the microscopic level. Later, the ultrafast transient absorption spectroscopy are carried out to investigate excition dynamics within the quantum dots films, which are studied to reveal the influence mechanism of various B-site dopants on carriers transport performance. Also, the first-principles calculations are used to investigate the electronic structure and thermodynamic stability of cubic CsPbI3 affected by B-site dopant. Finally, a systematic theory is formed to guide the optimization of CsPbI3 and promote the commercial of inorganic perovskite solar cells.

无机钙钛矿CsPbI3，具有优异的光电特性，且对外部的光、热、电的稳定性较高，成为目前发展最为迅速的光伏材料。然而，由于铯、铅、碘离子半径不匹配导致其钙钛矿结构 (立方相) 的室温不稳定性，进而影响CsPbI3的薄膜质量。本项目针对CsPbI3薄膜制备过程中易相变，且薄膜中B位阳离子取代困难的关键问题，拟通过小半径阳离子对CsPbI3量子点进行B位掺杂调节，实现CsPbI3量子点电池长期稳定高效率的工作。同时，运用透射电子显微镜原位研究对比掺杂离子在量子点生长过程中所起的作用，在微观层面上揭示B位掺杂下的结构重组机制；利用超快瞬态吸收光谱等测试手段研究激子动力学问题，阐述掺杂离子对载流子传输性能的影响机制；并进一步通过第一性原理计算B位掺杂对CsPbI3的电子结构及热力学稳定性的影响。最终，形成系统的理论指导CsPbI3材料的优化处理，促进钙钛矿太阳能电池的商业化进程。

CsPbI3 钙钛矿太阳能电池因其热稳定性、合适的带隙和优异的光电性能而得到迅速发展。然而，由于Cs+ (1.88 Å)半径较小，使得容忍因子较小，偏离理想值(0.9–1.0)，导致CsPbI3极易从黑色相转变为黄色非钙钛矿相，从而降低CsPbI3电池性能。因此，稳定相结构对于提高CsPbI3 PSCs的功率转换效率至关重要。基于此，探索了引起相结构不稳定的内在及外在因素，通过溶剂工程调控溶剂与溶质间的相互作用，改善薄膜结晶动力学，实现相结构的稳定及载流子的高效传输；通过引入双层CsPbX3量子点材料，钝化CsPbI3薄膜以及优化能级结构，建立了额外的电荷传输通道；通过对CsPbX3进行A、B及X位掺杂，调节带隙及薄膜光电性能，实现高性能CsPbI3电池的构筑。最终获得效率超过19%且稳定性较好的CsPbI3太阳能电池。这些工作对CsPbI3电池性能的进一步提高具有指导意义。