有机无机卤化物钙钛矿的奇异材料特性：离子行为和载流子空间分离，及其对钙钛矿光伏器件的影响

Although perovskite solar cells exhibited unprecedented potential of high efficiency and low cost, this new technology still faces some important problems: firstly, the origin and solution of the current-voltage hysteresis; secondly, the long-term stability of the perovskite solar cells; thirdly, the mystery of the very low carrier recombination loss exhibited in the organic-inorganic halide perovskites. .Recent works have revealed two unique material properties of the organic-inorganic halide perovskites: one is the existence of a large number of mobile ions in the materials; the other is the spatially separated charge densities of electrons and holes in the materials. The first property is expected to fully explain the hysteresis phenomenon; and the second one can explain the very low carrier recombination-loss of the organic-inorganic perovskites..This project aims at the important issues encountered in the field of perovskite solar cells. We propose to continue the investigation of these two unique material properties. The research focuses on the origin and the drift mechanism of the mobile ions, as well as their effects on the device performance, especially the long-term stability. We will also continue to study the phenomenon of charge carrier separation in the organic-inorganic perovskites, focuses on the experimental verification, and accordingly search for better photovoltaic materials.

虽然钙钛矿太阳能电池表现出前所未有的高效率和低成本潜力，这项新技术仍然面临几个重要问题：一是器件表现出的电流电压迟滞（hysteresis）现象的产生原因以及克服办法；二是钙钛矿太阳能电池的稳定性问题；三是有机无机钙钛矿材料表现出的极低载流子复合损耗之谜。.近期的工作揭示了有机无机卤化物钙钛矿两个奇异的材料特性：一是此材料中存在大量的可移动离子；二是该材料中电子和空穴的电荷密度在空间上显著分离。第一个材料特性有望全面解释hysteresis现象的起源；第二个可以解释有机无机钙钛矿材料非常低的载流子复合损耗的来源。.本项目拟针对钙钛矿太阳能电池领域当前面临的重要问题展开研究。基于最近对该材料两个奇异特性的发现，深入研究有机无机复合型钙钛矿中离子的产生和传输机制及其对钙钛矿太阳能电池性能的影响；并继续研究有机无机钙钛矿中电子和空穴空间分离的规律，着重实验验证，并依照这个规律探寻更优异的光伏材料

虽然有机无机钙钛矿太阳能电池表现出前所未有的高效率和低成本潜力，这项新技术仍然面临电流电压回滞和器件的工作稳定性问题。本项目研究了有机无机钙钛矿的离子特性和回滞以及稳定性的关系。具体包括：测量了有机无机钙钛矿材料的离子电导率，离子激活能；发现了钙钛矿电化学发光器件（LECs）；改变和优化了多种载流子传输层组分和结构，在多个器件结构中消除了回滞现象；研究了混合阳离子和混合阴离子组分的钙钛矿材料的材料和器件，发现混合离子钙钛矿比MAPbI3光稳定性大幅度提高；研究了钙钛矿器件的稳定性和电场依赖性，发现离子的迁移和聚集确实是影响器件寿命的重要因素；用第一性原理方法计算和预言了多种性能更加优异的新型钙钛矿材料；改善钙钛矿薄膜的组分，提高薄膜质量，增大的晶粒尺寸，降低缺陷和无辐射缺陷态密度等，目前实验室钙钛矿太阳能电池的认证效率已经达到21.4%。改变和优化了多种载流子传输层组分和结构，采用离子阻隔方法实现了器件寿命的大幅度提高，目前实验室制备的器件经过1000小时的光照后，效率仍保持初始值的90%以上。