界面电子动态对钙钛矿光伏器件性能影响研究

Perovskite-based photovoltaic (PV) of remarkable power conversion efficiency (PCE) approaching 20% is of widespread interest. The PCE of perovskite PV device sharply increase from ~4% to ~15% within 4 years, leapfrogged the parallel research such as organic photovoltaic (OPV) and dye-sensitized solar cells (DSSC) in 2013. It combines the advantages of OPV and DSSC, and exhibits a comparable performance (in term of efficiency and stability) with inorganic solar cell. Albeit with fascinating efficiency achieved in perovskite-structured PV device, the knowledge on the underlying principle, especially for perovskite-based device with various structures, is limited. A direct insight into the fundamental electronic energetics and the optoelectronic properties of the hybrid organic-inorganic-based perovskite devices are of high importance as they provide fundamental guidance for current perovskite-based device, as well as a new research pathway for future development and device enhancement. In contrast to organic dyes, the mixing methylammonium tin and lead halides with perfect crystalline perovskite structures exhibit low exciton binding energies and high conductivities. Their applications as light-absorbing dye (and/or hole transporting layer HTL) therefore lead to striking PCE in prior to traditional organic dyes. Along with the new breakthrough of 15.6% PCE launched by Snaith et al. using perovskite materials with multi-layer planar cell structure in 2013, the interfaces and their electronic structures become important factors that drive the overall light-conversion efficiency of the perovskite-based solar cells. Although burgeoning efforts were devoted on the materials design/ synthesis of perovskite materials, there is so far no report on its electronic energetics such as the density-of-states (DOS) distributions, work function, band gap, energy levels alignment, etc. Herein, the investigator aims to study the electronic properties of the perovskite materials and shed light on the fundamental physics and electronics for the nature and working mechanism of perovskite-based solar cell. The electronic knowledge developed would provide important guidance for tailoring the performance of the metal-organic hybrid perovskite-based solar cells. This project not only provides important guidance on tuning and tailoring the properties of perovskite materials, but also energetic constraints that theoretically bound the performance (such as the Voc and the Jsc) of the forming device. The findings of this research would be scientifically and technically important for current understanding and future development applications of perovskite PV devices.

有机/无机混成钙钛矿高分子光伏器件凭借其高电转换效率（PCE）一直倍受关注。该光伏器件的PCE四年间由4%大幅跃升至15%，效率已远超过有机及染料敏化太阳能电池，达到可媲美无机太能电池的程度。 钙钛矿材料具有低激子结合能与高导电性等特点，一般认为其吸光/传电性能较传统有机染料有效。Snaith团队去年以多层平面设计构建了PCE达15.6%的钙钛矿光伏器件。此突破暗示材料间的电子能带结构与电子动态，对器件性能有着密切关系。然而，目前人们对钙钛矿材料的光电效应与工作机理认知仍处以起步阶段。真实界面电子结构分析，不但能为器件原理制定理论基础，还能为设计高性能器件提供指引。但遗憾的是目前国内外对此新钙钛矿材料的电子特性(如电子态分布、功函数和界面能带结构等)研究仍相对滞后。本项目因此旨在为钙钛矿材料的电子特性及其微观光电子动态作系统研究，为其光电转换机制提供理论基础及实验依据。

钙钛矿材料由于其光谱吸收范围较宽，激子结合能较低，电荷传输距离远等优点，展现出了比有机和染料太阳能电池更高的效率，目前其效率已经可以与最高的无机硅太阳能电池相比。虽然钙钛矿太阳能电池在效率上得到了较大的突破，人们对于不同钙钛矿电池结构的光电机理的理解仍然很有限。在本项目中我们为新型钙钛矿太阳能电池的发展提供了直接的理论及实验依据。.在本項目，研究小組对钙钛矿材料的光电效应与工作机理深入研究。揭示并阐明了钙钛矿材料的界面电子结构分析，为器件原理制定理论基础，还为设计高性能器件提供指引。我们使用了溶剂热，能带有序排列，减小无机层间距，界面修饰等多重的方法来提高了不同结构钙钛矿的光电转化效率。其研究结果，已分别发表在19份不同的文献杂志。