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The Origin of Non-Radiative Losses in Metal Halide Perovskites

金属卤化物钙钛矿非辐射损失的起源

基本信息

批准号：
EP/R023980/1
负责人：
Samuel Stranks
金额：
$ 34.81万
依托单位：
University of Cambridge
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2018
资助国家：
英国
起止时间：
2018 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FR023980%2F1
关键词：
Origin Non Radiative Losses Metal

项目摘要

Solar cells and light-emitting diodes (LEDs) made from novel, inexpensive materials have the potential to be low-cost, clean and scalable solutions to supply our growing electricity and lighting demands. While solar cells convert sunlight into electrical energy, LEDs are the reverse, with electrical energy transformed into emitted light. Metal halide perovskites are extremely promising materials for both applications. Perovskite solar cells have improved their power conversion efficiency from 3% to 22% in just three years, approaching that of the market-leading technology, silicon (25%). Early reports of perovskite LEDs are also encouraging though relatively unexplored. Perovskite ingredients are abundant and can be combined inexpensively into thin films with a crystalline structure similar to silicon. Rolls of thin, flexible perovskite film could one day be rapidly spooled from a special printer to make lightweight, bendable, and colourful solar and light-emitting sheets.Nevertheless, the full potential of perovskites has not yet been realised. Strong light emission is essential for both solar cells and LEDs to reach their theoretical efficiency limits, but emission and therefore performance is still limited by parasitic emission loss pathways that are still poorly understood. The films are made up of densely packed crystals (grains) and we hypothesise that each grain has slightly different local chemistry and structural properties, some of which are defective. The ultimate aim of this work is to determine the fundamental origin of these loss pathways in perovskite films and full devices by elucidating which are the optimal chemical and structural properties, and using this information to achieve optimal films.This aim will be achieved by measuring the grain-to-grain emission using a novel microscope system which will allow rapid imaging of the emission with high spatial resolution. Most microscopic emission measurements on perovskites to date have employed confocal microscopes in which the emission is mapped by taking sequential measurements of the spectra of adjacent regions and moving the sample point by point until the region of interest has been covered. On the other hand, imaging consists of focusing the image of a sample on a detector and measuring for each pixel the intensity of light at one particular wavelength, much like taking a photograph, but at a single wavelength. In some applications, the power of the laser used in imaging can be orders of magnitude higher than in mapping, since the power is spread over the whole region instead of a single point, thus allowing measurement under device-like conditions. Imaging also permits a higher resolution and reduces the acquisition time by orders of magnitude.Emission images under both light (photoluminescence) and when applying an electrical bias (electroluminescence) will be acquired. The emission images of the same scan area will then be directly correlated with maps of the local grain-to-grain chemistry using electron microscopy techniques including energy-dispersive X-Ray (EDX) spectroscopy and local structural measurements using a nano-X-Ray Diffraction (n-XRD) beamline at the Diamond synchrotron. The work is highly timely and the results will provide a platform for efforts to take perovskites to their efficiency limits. The work will reveal the specific preferred chemistry and structural properties which must be targeted for growth of higher performing perovskite films and also reveal insights into potential post-treatments capable of healing defects in the perovskite materials. This will be of strong interest to a range of academic researchers in the perovskite field as well as industrial entities such as UK-based Oxford PV, which is leading the current commercialisation efforts of this exciting technology. Finally, the project will allow the PI to establish his team as a world-leading group with a cutting-edge programme and toolset.

由新型廉价材料制成的太阳能电池和发光二极管（LED）有可能成为低成本、清洁和可扩展的解决方案，以满足我们不断增长的电力和照明需求。太阳能电池将太阳光转化为电能，而LED则相反，电能转化为发射的光。金属卤化物钙钛矿是用于这两种应用的非常有前途的材料。在短短三年时间里，Percent太阳能电池的功率转换效率从3%提高到22%，接近市场领先的硅技术（25%）。钙钛矿LED的早期报告也令人鼓舞，尽管相对未经探索。Peroxide成分丰富，可以廉价地组合成具有类似于硅的晶体结构的薄膜。有一天，一卷又一卷的柔性钙钛矿薄膜可以从一台特殊的打印机上快速卷绕起来，制成重量轻、可弯曲、色彩鲜艳的太阳能和发光板。然而，钙钛矿的全部潜力还没有实现。强光发射对于太阳能电池和LED达到其理论效率极限是必不可少的，但发射和因此的性能仍然受到寄生发射损失途径的限制，这些途径仍然知之甚少。这些薄膜是由密集的晶体（晶粒）组成的，我们假设每个晶粒都具有略微不同的局部化学和结构特性，其中一些是有缺陷的。这项工作的最终目的是通过阐明哪些是最佳的化学和结构特性，并使用这些信息来实现最佳的films.This目的将通过测量晶粒到晶粒的发射使用一种新型的显微镜系统，这将允许快速成像的发射具有高空间分辨率，以确定这些损失途径的钙钛矿薄膜和完整的设备的根本起源。迄今为止，大多数对钙钛矿的微观发射测量都采用共焦显微镜，其中通过对相邻区域的光谱进行连续测量并逐点移动样品直到覆盖感兴趣的区域来绘制发射。另一方面，成像包括将样品的图像聚焦在检测器上，并测量每个像素在一个特定波长下的光强度，就像拍摄照片一样，但在单一波长下。在某些应用中，成像中使用的激光功率可能比映射中高几个数量级，因为功率分布在整个区域而不是单个点上，从而允许在类似设备的条件下进行测量。成像还允许更高的分辨率，并将采集时间减少了几个数量级。将采集光下（光致发光）和施加电偏压（电致发光）时的发射图像。然后，使用电子显微镜技术，包括能量色散X射线（EDX）光谱和在金刚石同步加速器上使用纳米X射线衍射（n-XRD）光束线的局部结构测量，将同一扫描区域的发射图像与局部晶粒间化学的地图直接相关。这项工作是非常及时的，其结果将为钙钛矿的效率极限提供一个平台。这项工作将揭示特定的优选化学和结构特性，这些特性必须针对更高性能的钙钛矿薄膜的生长，并且还揭示了对能够修复钙钛矿材料中缺陷的潜在后处理的见解。这将引起钙钛矿领域一系列学术研究人员以及英国牛津光伏等工业实体的浓厚兴趣，牛津光伏正在领导这项令人兴奋的技术的商业化工作。最后，该项目将允许PI将其团队建立为具有尖端计划和工具集的世界领先团队。