钙钛矿太阳电池中具有界面钝化功能的小分子空穴传输材料的设计、合成及性能研究

In perovskite solar cells (PSCs), hole-transporting materials (HTMs) play a key role in the device efficiency and stability. However, the most efficient HTM (spiro-OMeTAD) has some problems, such as high price and excessive defects at perovskite/HTM interface, which limit the further improvement of device performance and large-scale application. In this project, we will introduce the function groups which can passivate the perovskite defects to the end position of low-cost HTMs, such as pyridine, carboxyl, cyano, amino. The interaction between these groups and perovskite can improve the interfacial contact of perovskite layer/hole transporting layer, reduce the binding energy and the trap distribution and depth at the interface. The obtained HTMs which own the dual function of passivating defects and transporting holes, which can realize rapid hole extraction, efficient passivation of perovskite traps and suppression of non-radiative recombination. Through exploring the interface structure, interaction, and trap distribution in the devices based on the HTMs with different passivation groups, we attempt to reveal the effect of passivation groups on the interfacial charge transfer kinetics, passivation mechanisms, and the photovoltaic performance, so as to obtain efficient HTMs which can passivate the interfacial defects (perovskite/HTM) and improve the performance of PSCs.

在钙钛矿太阳电池中，空穴传输材料（HTM）是影响器件效率和稳定性的关键因素之一，但是目前报道的最为高效的HTM（spiro-OMeTAD）存在着价格昂贵、与钙钛矿层之间界面处缺陷态过多等问题，限制了其性能进一步提高和应用。本项目拟将具有钝化钙钛矿缺陷态能力的吡啶、羧基、氰基、氨基单元引入到低成本小分子HTM末端，利用钝化基团与钙钛矿材料之间的相互作用，改善界面接触、降低两者之间的结合能和界面处缺陷态的密度及深度，使HTM同时具备钝化钙钛矿薄膜表面缺陷态和传输空穴的双重作用，实现快速抽取空穴、钝化界面缺陷态和抑制光生载流子非辐射复合的目的。同时，通过对基于含有钙钛矿缺陷态钝化基团HTM的器件内界面结构、相互作用及缺陷态分布的探究，揭示钝化基团的存在对电池界面的电荷传输动力学过程、钝化机理及光伏性能的影响机制，最终获得具备界面（钙钛矿/HTM）钝化功能的高效HTM，从而提升器件的性能。

钙钛矿太阳电池的性能在过去几年获得了极快的发展，光电转换效率已超过25%，表现出巨大的商业化应用前景。在钙钛矿太阳电池中，空穴传输层是影响器件效率和稳定性的关键因素，但是目前报道的最为高效的空穴传输材料spiro-OMeTAD存在着价格昂贵、无法有效钝化钙钛矿表面缺陷（如带正电低配位的金属离子、低配位的卤素离子等）等问题，限制了器件性能进一步提高和规模化应用。本项目成功将具有钝化钙钛矿薄膜缺陷态能力的吡啶、氰基路易斯碱单元引入到小分子空穴传输材料结构上，并系统研究了分子结构变化对其物化特性（如光物理、电化学、热稳定、载流子传输、疏水性等）及器件性能的影响，得到了同时具备钝化钙钛矿薄膜表面缺陷态和传输空穴双重作用的空穴传输材料，实现快速抽取空穴、钝化界面缺陷态和抑制光生载流子非辐射复合的目的。开发出的含吡啶及含氰基的空穴传输材料器件最高效率均达到18%左右，在相同条件下与传统spiro-OMeTAD和PEDOT：PSS相当，最主要的是，基于新材料的器件稳定性显著提升。本项目的研究结果也对钙钛矿太阳电池及其薄膜太阳电池更高效载流子传输材料和开发提供了理论参考。