卤化物半导体光伏材料的电子结构研究和性能优化设计

Clean energies such as solar cells have been paid to more and more attentions due to the shortage of fossil fuels and the severe pollution of environment. Photovoltaic materials play a great role in converting solar energy into direct current electricity. Although organic-inorganic perovskite solar cells based on halides containing Pb ions have made a great progress, designs and studies of environment friendly halide photovoltaic materials with high performance are indispensible. By employing first-principles method, we perform the studies of halide photovoltaic materials without Pb ions. Within the framework of density functional theory, methods at deferent levels will be tested to obtain accurate electronic structures, such as band structure, effective masses of carriers, density of states and optical absorption coefficients. Based on this, the properties of intrinsic defects and migration of defects will be studied. Van der Waals interaction has significant influence on crystal structure and the height of diffusion barrier and will be considered in our calculations. Previous studies of defects in organic-inorganic photovoltaic halides containing Pb ions seldom take into account Van der Waals interaction which originates from the fluctuations of long range electron-electron correlation. We will investigate the correlation between the structure and properties of halides and aim to design and find environment friendly and earth abundant halide photovoltaic materials. This study will deepen our understanding of halides and supply guideline for experiments.

清洁能源的使用如光伏电池在解决传统化石燃料的短缺和减轻环境的污染方面受到了越来越多的重视。半导体光伏材料的性能在提高光和电之间的转换效率方面起着决定性的作用。虽然含铅钙钛矿卤化物光伏材料取得了一定的进展，但研究环境友好、高效的半导体光伏材料仍有着重要的意义和价值。本课题拟采用第一性原理方法，开展新型无铅卤化物半导体光伏材料的研究。首先在密度泛函理论的框架下使用不同层次的计算方法得到准确的电子结构，如能带结构、载流子有效质量，以及光学吸收系数等。在此基础上，研究卤化物中的本征缺陷以及缺陷扩散性质。计算模拟时考虑对晶体结构、缺陷扩散势垒有着重要影响的范德瓦尔斯作用。已有的含铅卤化物缺陷计算很少考虑起源于电子间的长程关联效应的范德瓦尔斯力。本项目拟探究卤化物物性与微观结构之间的关联，计算设计新的环境友好、价格低廉的高效卤化物光伏半导体材料；加深对卤化物的理解，为实验提供有益的知识储备。

清洁能源的使用以及提高不同形式能量之间的转化效率在解决环境污染方面受到了越来越多的重视。该项目主要关注卤化物钙钛矿半导体光电子材料在上述领域应用的理论基础研究。我们研究了卤化物半导体材料的电子结构、缺陷性质，输运及光学性质。我们发现ns2孤对电子对卤化物激发态结构弛豫和光学性质有着重要的影响，拓展了其对能带结构、载流子有效质量以及输运性质影响的认识。我们初步掌握了此类材料的输运及光学性质跟材料的结构以及组成元素之间的内在关联，为进一步的研究提供了初步的理论基础。依托该项目，最终发表包括PRB、PRM、JMCC、JAP和Angewandte Chemie International Edition在内的SCI论文7篇。此外，项目负责人获得北航青年拔尖人才计划。在本项目的支持下培养了三名在读硕士和两名博士。