基于垂直取向石墨烯/TiO2多级孔道结构的钙钛矿太阳电池电子传输层研究

Perovskite solar cells (PSCs), because of their excellent photoelectric properties, easy processing and broad application prospects, have become an issue in the new type, efficient thin-film solar cells now, and the current efficiency is 22.1%. Whereas, the high steric hindrance of grain boundaries in the electron transport, the imperfect interface contact of electron transport layer/perovskite layer, and the unstable device in the solar cells limit the PSCs to obtain higher photovoltaic performance and commercial application. This project prepares a composite film composed of vertically orientation graphene and spherical TiO2 nanomaterials as the electron transport layer, which provides rapid electronic transport channels in the vertically orientation graphene and multiple porous structure in the spherical TiO2 nanomaterials. Utilizing the synergistic effect of vertically orientation graphene and spherical TiO2 nanomaterials could accelerate the electron transport in the electron transport layer, improve the contact interface of perovskite/graphene-TiO2 nanomaterials and reduce the trap distribution in the interface, achieving the purpose of rapid electron injection, transport and collection, and inhibited electron recombination, which could further improve the photoelectric performance of PSC; Through exploring interface structure, energy level structure, and trap distribution of the composite film on the effect of quality, morphology and crystallinity of perovskite films reveals the mechanisms of photovoltaic performance, interface charge transfer kinetics and stability, so as to obtain high-performance device and promote the development of commercialization.

钙钛矿太阳电池(PSCs)因其优异的光电性能、易加工且具有巨大应用前景，成为新型、高效薄膜太阳电池的研究热点，目前效率已达22.1%。但器件的电子传输层中存在晶界位阻高、缺陷态多和电子传输层/钙钛矿层界面接触不理想等问题，限制了其性能进一步提高和商业化应用。本项目拟制备垂直取向石墨烯/跨尺寸球形TiO2纳米颗粒多孔复合薄膜，并将其作为PSC的电子传输层，利用垂直取向石墨烯定向电荷高速传输特性以及与跨尺寸球形TiO2纳米颗粒自组装成多级孔道结构的协同作用，提供电子快速传输通道并改善钙钛矿材料与石墨烯-TiO2间的界面接触，减少界面处缺陷态的分布，实现快速抽取电子、高速传输电子同时抑制电子复合的目的，从而进一步提高PSC的光电性能；通过对器件内界面结构、能级结构以及缺陷态分布的研究，揭示电池的界面电荷传输动力学过程和光伏性能的影响规律和机制，获得高效的电池器件，有助于其商业化的发展。

在过去10年中，钙钛矿太阳电池表现出前所未有的发展速度。虽然其认证效率达到25.5%，但仍有许多问题亟待研究者们去思考和解决。其中，钙钛矿太阳电池中光生载流子的产生、复合、分离、输运和收集过程决定着其光伏性能。电子传输层、钙钛矿活性层以及电子传输层与钙钛矿层的界面对这些过程有着重要影响。为了提高钙钛矿太阳电池的转换效率，需要增强电子在钙钛矿层和电子传输层中的输运以及其在电子传输层与钙钛矿层界面处的分离，需要抑制电子传输层与钙钛矿层界面以及钙钛矿层内部的非辐射载流子复合。高质量的电子传输层对于这些至关重要。本项目从增强电子转移和输运、抑制非辐射载流子复合的角度出发，采用合成单晶TiO2纳米颗粒，体相掺杂和界面修饰等策略对电子传输层和钙钛矿活性层进行改性研究，减少器件的非辐射复合，加快电子的传输与收集，进而提升器件的光电性能。目前基于单晶菱形TiO2纳米颗粒的电子传输层，实验室效率达到23.98%，认证效率为23.5%。因此，本项目开发出的单晶菱形TiO2纳米颗粒的电子传输层将完全替代商业化澳洲Dyesol产品的电子传输层，并表现出更佳的光电性能。