基于无机非晶电子转移层的柔性钙钛矿太阳能电池性能调控及其机制研究

High-efficiency perovskite solar cells (PSCs) have enormous application prospects, among which flexible PSCs are gaining increasing attentions particularly because of their lightweight, bendable, and portable features. Currently inorganic crystalline semiconductor materials are mostly employed in PSCs as electron transfer layer (ETL), but which has impeded the developments of flexible PSCs due to the high fabrication temperature of such materials, and thus the key to solve this problem is how to fabricate ETL at low temperature. In this proposal, we put forward a sol-gel method to manufacture high-efficiency flexible PSCs based on low temperature processed WOx and SnOx amorphous ETLs. We will go deep into their photovoltaic characteristics and the chemical processes occurred in the low temperature fabrications, meanwhile, the optimizations of both bulk and interface structures will be thoroughly investigated. Through the realization of controllable preparations of such amorphous ETLs，we will analyze their semiconductor characteristics involving the band gap structure and defect categories systematically. Furthermore, we will develop a deliberate strategy based on heteroatom-doping to modify the properties of the amorphous semiconductor and to elucidate the mechanisms which refer to the regularities of impact that the interfacial microstructures have on the charge transfer dynamics. The coupling effect between ETL and perovskite layer will be strengthened by the chemical modifications of interfacial monolayer, which will achieve facilitated interfacial charge separation and suppressed interface degradation, and in turn enhance devices’ conversion efficiency and stability. This proposal will provide a strong theoretical and technical support on the study of high-efficiency and stable flexible PSCs.

高效率钙钛矿太阳能电池（PSCs）具有良好应用前景，而柔性PSCs因质量轻、可弯曲等优点而备受关注。PSCs电子转移层（ETL）目前普遍使用晶态半导体材料，较高的制备温度严重制约柔性PSCs发展，因此，低温制备ETL现已成为解决这一问题的关键。本项目提出采用溶胶-凝胶法低温制备（< 100 ℃）WOx和SnOx两种无机非晶ETL，并构筑高性能柔性PSCs。我们拟对材料低温制备化学过程、薄膜和界面结构调控以及PSCs光电特性进行研究。在实现非晶ETL可控制备的基础上详细阐明其能带结构和缺陷态类型等半导体特性，进一步发展以杂原子化学修饰为基础的非晶半导体性能调控策略，揭示界面微观结构对电荷转移动力学的影响规律，通过界面单分子层化学修饰强化ETL与钙钛矿层之间的耦合作用，以此促进电荷界面分离并抑制界面衰退，进而提高器件效率和稳定性。本项目将为研制稳定高效的柔性PSCs器件提供理论依据和技术支持。

柔性钙钛矿太阳能电池（F-PSCs）因质量轻、可弯曲等优点而备受关注，具有良好应用前景。F-PSCs电子传输层（ETL）的低温制备和界面调控是提升器件性能的关键。本项目首先研究了新型非晶态ETL的低温制备和缺陷抑制，发展了增强界面耦合的方法，制备出了高性能F-PSCs；为了进一步提升器件效率，开展了新型二维钙钛矿的制备及三维钙钛矿缺陷钝化研究；在此基础上，开展了新型碳基PSCs的研究。所取得的重要研究结果及科学意义如下：（1）发展了非晶态ETL普适性制备方法，揭示了薄膜杂质缺陷的种类和来源，并发展了一种基于臭氧辅助的低温制备方法，成功制备了高质量NbOx非晶薄膜，将其用作ETL获得高效率PSCs；通过控制界面水分子吸附，实现了SnO2电子传输层的原位低温结晶调控，制备出了转换效率超过19%的高性能F-PSCs。（2）通过设计“渗透型电子传输层/钙钛矿界面”增强了钙钛矿下界面耦合，通过2D/3D维度工程增强了钙钛矿上界面耦合，有效钝化了界面缺陷并促进了光生电荷转移，在本领域率先将F-PSCs效率提升至21%以上，器件机械稳定性也得以大幅提升，能够经受住20000次的反复弯曲。以上两部分的研究为ETL的低温制备和提升F-PSCs效率和稳定性提供了新思路和重要科学依据。（3）设计并制备出新型叠合式碳基PSCs，通过将电荷纵向提取和横向传输解耦，并结合单原子材料解决了相邻功能层之间的能级失配问题，大幅减少了电荷转移动力学能量损失，器件效率达到了21.6%，为目前碳基PSCs最高效率；本项工作从根本上摆脱了真空沉积技术和贵金属电极，大幅降低了器件成本并显著提升了器件稳定性，为PSCs产业化提供了重要解决方案。本项研究取得了丰硕成果，相继发表在Nature Energy, Joule, Energy & Environmental Science, Nature Communications等顶级期刊上。