Emergent Opto-Mechanical and Electro-Mechanical Coupled Behavior of Halide Perovskites

非技术描述所谓的“卤化物钙钛矿”是一种新型太阳能电池技术的核心材料。这些新的太阳能电池显示出巨大的前景，因为它们不仅在将阳光转化为电能方面非常高效，而且潜在的制造成本非常低。然而，这些新的太阳能电池材料的机械性能尚不清楚，特别是在太阳能电池的运行条件下：在阳光下，以及电流通过它们时。因此，研究和了解这些特性是非常重要的，因为它们决定了新的太阳能电池的长期耐久性，预计这些电池将在元件中高效运行20年或更长时间。为此，进行了系统的研究，研究了新型太阳能电池材料在光和/或电流作用下的下列相关力学性能：(1)裂纹的开裂和愈合；(2)塑性变形；(3)随时间变化的变形。这些研究是在化学成分、构型和形态定义良好的材料上进行的。对这些研究的结果进行了严格的分析，以了解新的太阳能电池材料的行为。预计这将对制造未来高耐用、低成本太阳能电池的能力产生广泛影响，并帮助这种新的太阳能电池技术充分发挥其潜力。作为这一努力的一部分，来自杜加鲁学院的未被充分代表的少数民族本科生研究人员得到了培训。这充分利用了布朗大学和Tugaloo学院之间长达50年的合作关系，Tugaloo学院是一所历史悠久的黑人学院或大学。公众推广活动的目的是加深公众对科学、工程和技术概念的理解。这需要利用布朗大学久负盛名的科学卡通(SciToons)计划，创建两个新的SciToon：新兴太阳能细胞技术和材料强度。技术说明有令人信服的理由表明，卤化物钙钛矿材料具有引人入胜的丰富的光机和机电耦合行为，但这一领域的研究极其匮乏。考虑到卤化物钙钛矿在新型太阳能电池和其他器件中具有前所未有的前景，必须更深入地了解卤化物钙钛矿的机械降解以及器件中普遍存在的光和/或电刺激。为此，这个项目来得正是时候，它涉及四个相互关联的任务，以及其中的几个子任务。在任务1中，对电场对卤化物钙钛矿单晶和薄膜的断裂和裂纹愈合行为的影响进行了实验和定量的研究。任务2包括定量研究卤化物钙钛矿单晶的塑性变形，以及光的影响(光塑性)。在任务3中，研究了电场对卤化物钙钛矿块体多晶球团随时间蠕变变形的影响。软卤化物钙钛矿中光载流子的有效产生和离子的易迁移有望通过它们与卤化物钙钛矿中的点和线(位错)缺陷的相互作用来调节裂纹愈合、塑性和蠕变现象。最后，在任务4中，作为例子，展示了光塑性效应在设备中的表现。布朗大学开发的项目所需的相当大的研究基础设施得到了充分利用。这项研究为开发下一代钙钛矿型太阳能电池和其他设备提供了科学基础，这些设备更高效，更重要的是更耐用。因此，这项研究预计将具有很高的影响力，并对研究人员和技术开发人员同样有用。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical DescriptionSo-called ‘halide perovskites’ are a family of materials at the heart of a new type of solar-cell technology. These new solar cells are showing great promise as they are not only highly efficient in converting sunlight into electricity but also potentially very inexpensive to manufacture. However, the mechanical properties of these new solar cell materials are not known, especially under operating conditions of a solar cell: in sunlight, and also when electric current is passing through them. Thus, it is very important to study and understand these properties because they determine the long-term durability of the new solar cells, which are expected to operate efficiently for twenty years or more in the element. To that end, systematic research is conducted, where the following relevant mechanical properties of the new solar cell materials are studied under light and/or electric current: (1) cracking and healing of the cracks; (2) plastic deformation; and (3) time-dependent deformation. These studies are conducted on materials of well-defined chemical compositions, configurations, and morphologies. The results from these studies are analyzed critically to understand the behavior of the new solar cell materials. This is expected to have a broad impact on the ability to make highly durable, low-cost solar cells of the future, and to help this new solar-cell technology then reach its full potential. As part of this effort, underrepresented minority undergraduate researchers from Tugaloo College are trained. This leverages the fifty-year old partnership between Brown University and Tugaloo College -- an Historically Black College or University. The public outreach effort is aimed at enhancing the public's understanding of concepts in science, engineering, and technology. This entails leveraging the well-established science cartoons (SciToons) program at Brown University for creating two new SciToons on: ‘Emerging Solar Cells Technologies’ and ‘Strength of Materials.’Technical DescriptionThere are compelling reasons to suggest there are fascinating, rich opto-mechanical and electro-mechanical coupled behavior in halide perovskite materials, yet there is extreme paucity of research in this area. Considering the unprecedented promise of halide perovskites for new types of solar-cell and other devices, it is imperative to have a more in-depth understanding of the mechanical degradation of halide perovskites coupled with optical and/or electrical stimuli that are ubiquitous in devices. To that end, this project comes at a highly opportune time, and it entails four interrelated Tasks, and several Subtasks within. In Task 1, the effect of electric field on the fracture and crack-healing behavior in halide perovskite single-crystals and thin films is studied experimentally and quantified. Task 2 involves the quantitative study of plastic deformation of halide perovskite single-crystals, and the effect of light (photoplasticity). In Task 3, the effect of electric field on the time-dependent creep deformation of halide perovskite bulk polycrystalline pellets is studied. The efficient generation of photocarriers and facile ion migration in soft halide perovskites are expected to mediate crack-healing, plasticity, and creep phenomena, through their interactions with point and line (dislocations) defects in halide perovskites. Finally, in Task 4 the manifestation of photoplasticity effects, as an example, are demonstrated in devices. The considerable research infrastructure needed for the project developed at Brown University is leveraged fully. This research contributes to the scientific foundation for the development of next-generation perovskite solar-cell and other devices that are more efficient, and importantly more durable over the long term. As such, this research is expected to be highly impactful, and useful to researchers and technology developers alike.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.