共轭聚合物对钙钛矿薄膜的界面自组装及其光伏器件稳定性的研究

One of the most challenge issues of perovskite solar cells is the moisture stability. The inorganic-organic perovskite contains the methylammonium ion, which is very sensitive to the moisture, resulting in a deficient device stability. In our former research, the excellent improvement on the device stability can be achieved using a novel conjugated oligothiophene derivative with high hydrophobicity as the hole transporting materials for perovskite solar cells. It can efficiently protect the underlayer of perovskite from moisture as well as work for the hole transporting and collecting. The introduction of this “bifunctional layer” was proven to be an effective strategy to improved the stability of perovskite solar cells..In this project, the interfacial assembly technique will be applied to form the moisture blocking/hole transporting bifunctional layer, which is aiming to fabricate a perovskite solar cells with high power conversion efficiency and stability. By interfacial assembly technique, the hydrophobic conjugated polymer can be deposited onto the hydroscopic perovskite substrate more easily with the anchoring groups. As a result, highly uniform and dense bifunctional film can be obtained to protect the perovskite film from moisture more effectively. Moreover, the anchoring points can provide the pathways for the carriers to transport through the interface, resulting in a reduced charge recombination and an increased charge collection efficiency of the device. This research presents a feasible and effective method to fabricate highly performed perovskite solar cells with improved stability, without increasing the complexity of the device structure, which is the very necessary and emergency study facing the successful development and commercialisation of perovskite solar cells.

近年来，钙钛矿太阳能电池的效率迅速突破了20%，但钙钛矿易潮解、水汽稳定性差是其实现产业化应用的主要障碍。申请者在前期工作中证实，在钙钛矿上层利用疏水性共轭聚合物构建水汽阻挡／空穴传输双功能层是提高器件水汽稳定性卓有成效的方法。在此基础上，本项目创新性地提出采用自组装技术来进行水汽阻挡／空穴传输双功能层的构建，该方法可形成均一、连续的共轭聚合物层，构成致密的疏水屏障；同时，自组装的位点可以促进电荷在二者界面的有效传输，进而提高电池的性能。因此，在显著提升器件稳定性的同时，确保器件的高效率工作。此项研究在不增加结构工艺复杂性的基础上，为制备高效率、高稳定性的钙钛矿太阳能电池提出了新的、符合实际应用需求的方案。

有机-无机杂化钙钛矿材料具有非常优异的光伏性能，其电池器件可以获得很高的能量转换效率，但其本身薄弱的水汽稳定性是制约其应用的一大瓶颈。本项目围绕钙钛矿太阳能电池的水汽稳定性，提出设计疏水性的空穴传输材料，在钙钛矿上层构建水汽阻挡/空穴传输双功能层。在项目的执行过程中，设计制备了新型的含氟的共轭高分子以及共轭高分子/石墨烯复合材料分别作为双功能层。通过材料的设计和工艺的调整，疏水性的双功能层实现了与亲水钙钛矿层的紧密接触，在此过程中目标分子还填平了钙钛矿晶体之间的缝隙，部分进入了晶界。这些材料本身优异的空穴传输性能，更为平整的界面，以及目标分子对晶界缺陷的钝化作用，使得修饰后器件的电荷传输性能有了明显的提升，器件的能量转换效率也随之提高。使用上述的两种材料均获得了最高20%以上的能量转换效率，且不存在明显的回滞效应。.更重要地，疏水性双功能层的引入有效得阻挡了水汽对下层钙钛矿薄膜的渗透，减缓了高湿度下水汽对钙钛矿薄膜的侵蚀，显著提升了钙钛矿太阳能电池的水汽稳定性。未经封装的钙钛矿太阳能电池器件在相对湿度40-50%的环境中储存40天以上，依旧可以保持最高效率的85%-90%。此项研究面向商业化及实际应用的需求，为制备高效率、高稳定性的钙钛矿太阳能电池提出了新思路和新方法。