钙钛矿电荷传输性能调控及电荷输运与复合机理研究

Charge transport materials (CTMs) closely relate to large-area power conversion efficiencies (PCEs), reproducibility, and stability of perovskite solar cells. So far, based on the reported electron and hole transport materials (ETMs & HTMs), the device efficiency over 20% has been achieved for small illuminated areas, but the carrier mobility and conductivity of these materials are still low, which is one of the reasons for poor reproducibility and large-area PCEs. Besides, the most widely used ETM, TiO2, can generate deep-level defects and holes with strong oxidizing power under ultraviolet light, and some HTMs or their dopants have a tendency to absorb water. These accelerate the device performance degradation, and the device stability still remains an issue for long-term use. This proposal focuses on the above problems, and a research plan about controlling the semiconductor characteristics and charge-transport of perovskites by their composition, preparation procedures, and doping is proposed to develop perovskites with predominant electron or hole transport properties, according to our previous research on semiconductor characteristics as well as perovskite solar cells. Based on this, devices with perovskite charge-transport layer will be fabricated. The effects of the perovskite charge-transport layer on device performance will be studied, and its mechanism for charge transport and recombination will also be uncovered. The device reproducibility and large-area PCEs are expected to be enhanced due to the high carrier mobility and conductivity of the perovskite CTMs, and the device stability is also expected to be improved by overcoming the above drawbacks accelerating the device performance degradation. The implementation of this proposal will offer a novel idea to design CTMs.

电荷传输材料与钙钛矿电池的大面积效率、再现性和稳定性密切相关。目前报导的电子和空穴传输材料（ETM & HTM）已取得20%以上的小面积器件效率，但其载流子迁移率和电导率仍较低，是器件性能再现性差、大面积效率低下的原因之一。此外，使用最广的ETM（TiO2）在紫外光照下可产生深能级缺陷和强氧化性空穴，一些HTM易吸水潮解，均会加速钙钛矿层的劣化。本项目针对这些问题，在研究半导体特性和钙钛矿电池的基础上，提出通过成分、制备工艺和掺杂调控钙钛矿的半导体特性和电荷传输性能，获得以电子或空穴传输为主导的钙钛矿材料。在此基础上，开发基于钙钛矿电荷传输层的原型器件，研究该电荷传输层对器件性能的影响，并探明其电荷输运与复合机理。该电荷传输材料具有高载流子迁移率和电导率，可提高器件的再现性和大面积效率，而且可克服上述加速器件劣化的缺陷，有助于提高器件的稳定性。本项目将为电荷传输材料的设计提供新的思路。

本项目着重对钙钛矿材料的界面电荷传输与复合开展了研究，主要包括钙钛矿/空穴传输层、钙钛矿/电子传输层界面和钙钛矿内部晶界。利用瞬态吸收光谱、时间分辨荧光、交流阻抗和空间电荷限制电流等手段对钙钛矿界面处的载流子输运与复合动力学开展了研究，从而揭示了其机理。在此基础上，制备了相关的钙钛矿太阳电池原型器件，研究了器件的光电转换性能和稳定性，揭示了优化钙钛矿界面电荷传输的方法。主要研究内容包括：.（1）钙钛矿材料的电荷传输性能可调，开发新型电荷传输材料.利用小分子有机半导体酞菁、双层钙钛矿结构（CH3NH3PbClXI3-X/CH3NH3PbI3）和聚偏二氟乙烯-co-六氟丙烯（PVDF-HFP）聚合物分别对钙钛矿/空穴传输层、钙钛矿/电子传输层界面和钙钛矿内部晶界的电荷传输性能进行了调控。利用酞菁和CH3NH3PbClXI3-X/CH3NH3PbI3结构分别改善了spiro-OMeTAD和TiO2的电荷传输性能。.（2）探明新型电荷传输层的工作原理及其电荷输运与复合机理，提高钙钛矿电池的大面积效率、再现性和稳定性.探索了酞菁、CH3NH3PbClXI3-X/CH3NH3PbI3结构和PVDF-HFP聚合物调控电荷输运与复合的机理：钝化晶界和提高载流子迁移率等。提高了钙钛矿太阳电池的效率和稳定性：最高效率接近20%，在未封装条件下工作500小时，其效率衰减率小于10%。