在器件工作条件下探索有机体异质结和钙钛矿太阳能电池动态给体-受体分子界面和电极界面处光伏过程

Organic solar cells have attracted tremendous research interests due to facile device-fabrication procedures, semi-transparent features, and mechanically-flexible properties. The efforts from materials synthesis and device engineering have led to continuous advancements on photovoltaic efficiencies quickly exceeding 10 %. More recently, using perovskite materials has led to surprisingly high photovoltaic actions with the efficiencies reaching 15 % from simple device designs. These quick advancements bring a fundamental demand to the field: revealing deeper internal photovoltaic processes at dynamic donor:acceptor (D:A) and electrode interfaces under-device-operating condition. At this moment, the deeper internal photovoltaic processes at the dynamic D:A and electrode interfaces still remain largely un-revealed, forming a great challenge to further advance the field of organic solar cells. To respond to this great challenge, the project is proposed to comprehensively investigate the dynamic D:A and electrode interfaces under device-operating condition by using our previously defined unique experimental methods: magnetic field effects of photocurrent and photoinduced capacitance. The proposed research plans to address two timely-important issues: (i) controlling the electron-hole binding energies at D:A interface through polarization and energy parameters and (ii) enhancing the charge collection at electrode interface through dielectric effects in both bulk-heterojunction and perovskite solar cells. The research goal is to provide critical understanding and effective knowledge base to materials synthesis and device engineering for controlling the useful and non-useful photovoltaic processes at both D:A and electrode interfaces towards further photovoltaic advancements in bulk-heterojunction and perovskite solar cells.

因制备工艺简易、半透明以及柔性，有机太阳能电池拥有极大的发展前景，通过材料合成和器件设计，其效率已超过10%。最近，钙钛矿材料在太阳能电池里的应用取得重大突破，经过简单的器件设计，效率达到了15%。这为有机太阳能电池的发展带来了新的需求：深入揭示在器件工作条件下动态给体-受体分子界面和电极界面处内部光伏过程。目前，人们还不能深入解决这一关键科学问题，从而使有机太阳能电池发展面临着巨大的挑战。本项目将利用独特的实验手段：光电流磁场效应和光诱导电容测量，研究器件工作条件下动态给体-受体分子界面和电极界面，解决以下两个重大科学问题：(1)通过调节极化和能量参数调控给体-受体界面处电子-空穴对的束缚能；(2)通过介电效应提高电极界面处的电荷收集。研究目标是为材料合成和器件设计提供有效的理论基础，进而调控给体-受体分子界面和电极界面处有用和无用的光伏过程，促进有机体异质结和钙钛矿太阳能电池的发展。

有机太阳能电池给体-受体分子界面和电极界面是决定光电流和光电压的关键动态参数，本项目利用先进的光电流磁场效应和光诱导电容测量研究手段，深入揭示了工作条件下有机体异质结和钙钛矿太阳能电池中控制给体-受体分子界面处束缚能及电极界面处电荷积累的关键物理参数。实验发现光诱导电偶极相互作用可以极大地减小电子—空穴在给—受体界面的束缚能，其形成的漂移电池还能够促进电荷传输，从而提高电池器件的性能，该研究结果为降低激子束缚能进而提升有机光伏器件性能提供了新的思路和依据。其次我们发现钙钛矿电池电荷输运层的电极化与活性层的电极化表现出很强的关联，从而利用电荷输运层可以调控活性层中的辐射和无辐射复合过程，我们首次将具有光诱导极化性质分子引入电荷输运层及活性层，使得器件光伏性能得到明显提升。此外我们还深入揭示了钙钛矿太阳能电池独特的光浸及电流-电压回滞现象的产生机理，这对于深入理解钙钛矿太阳能电池工作机制和进一步提高钙钛矿电池性能具有重要意义。