有序钙钛矿型铁电材料的构建及光电性能研究

Development of highly efficient photoelectric materials is of great scientific and practical significance for the utilization of solar energy. How to promote separation of photo-generated carriers is one of the key issues determining the photoelectric properties of a semiconductor. Many studies have proved that junction structure fabricating and co-catalysts loading are effective approaches. However, these approaches only function at the interfaces between different materials. Little research effort has so far been devoted to exploring the feasibility of promoting the photo-carriers separation within the interior of the same material by internal electric field. This study is based on the consideration that spontaneous electric polarization of a polar semiconductor-perovskite ferroelectric material can be utilized to realize the spatial separation of photogenerated electrons and holes within the interior of a semiconductor by controlling and fabricating the assemblage state of the micro/nano-crystals. In this project, the self-assembled perovskite micro-structure with oriented electric domains will firstly be designed and fabricated. Then comprehensive characterization of the photoelectric properties of the materials will be carried out. Further fundamental understanding of the “structure-property” relationship for the perovskite material will be acquired in conjunction with fine characterization of domain states and local chemical structures. By optimizing the microstructure of the material, the separation of photogenerated electrons and holes within the interior of the samples can be effectively enhanced and highly efficient perovskite ferroelectric materials will be obtained. The knowledges to be developed in this project will provide the understanding of photoelectric effect mechanism for the role of the ordered domain states of a polar semiconductor, and broaden the photoelectric application of the perovskite ferroelectric materials.

设计和开发可高效利用太阳能的光电材料具有重要的科学意义和实用价值。提高材料光电性能的核心问题在于如何有效促进光生电子和空穴的分离。目前大部分的研究主要采用构建结形结构或担载助催化剂来促进光生电荷在不同物相界面的分离，对如何在同一材料内部通过微结构设计实现光生电荷分离的研究还未见报道。本项目选取极性半导体－钙钛矿型铁电材料为研究对象，充分利用其具有定向内建电场（电畴）的特性，通过构建紧密有序排列的铁电晶体微结构，结合电畴状态和微结构的精细表征，研究材料光电性能与内部微结构的关联和规律，实现光生电荷在同种材料内部的有效分离与传导，获得具有增强光电性能的钙钛矿型铁电材料。此研究独辟蹊径，不仅从有序极性半导体电畴结构这一崭新视角丰富对光电效应机理的认知，也对拓展钙钛矿型铁电材料在光电领域的应用具有重要意义。

以设计和开发可高效利用太阳能的光电钙钛矿材料为研究目的。从钙钛矿材料的晶体结构出发，通过改变钙钛矿结构ABX3中有机阳离子A基团，合成出一系列具有不同烷烃链及胺基数的二维层状有机-无机杂化钙钛矿化合物（如：乙胺铅碘、丙胺铅碘、乙二胺铅碘、二氨基丙胺铅碘等），系统研究了材料层状显微结构与光电性能之间的关联与规律，研究结果显示改变烷基链长或胺基数均直接影响钙钛矿材料的带隙宽度：随碳链的增加，带隙变大；而随胺基数的增加，带隙又急剧变小。二氨基丙胺铅碘钙钛矿材料光吸收边位置达到930 nm，并显示出良好的湿度稳定性；以二氨基丙胺铅碘钙钛矿材料为光吸收层，构建出具有一定光电转换效率的太阳电池。考虑到进一步解析具有新型烷烃链结构钙钛矿材料的详细晶体结构及制备顺应环保要求的钙钛矿材料出发，探索制备出具有新型烷胺基结构的钙钛矿晶体材料（如乙二胺铅碘、乙二胺铜碘等）。利用溶剂热法制备出有序紧密排列的钙钛矿型铁电材料（铌酸钠，铌酸钾钠），研究此类材料对有机染料及有机小分子气体的可见光催化作用。基于深入研究碳材料（碳纳米管、石墨烯）作为优质导电基体材料的需要，结合碳材料具有的优良导电性及稳定性，设计并制备出氢氧化镍填充、包裹碳纳米管复合材料以及氧化锌修饰碳纳米管的复合材料，从微观结构解析具有特殊形貌碳基复合材料的形成机理，研究发现碳纳米管的加入可显著提高复合材料的电学及电化学性能，有效促进光生电子-空穴的分离。这些研究成果对发展具有新型功能团的钙钛矿材料，实现可有效利用太阳能的稳定无毒的光电材料具有一定的指导意义。项目圆满完成，达到了预期结果。在项目实施过程中，正式发表SCI论文8篇，其中课题负责人以第一作者发表国际SCI论文4篇，申请发明专利5项。