CAREER: Modulating Optoelectronic Properties and Functionality of Hybrid Organic-Inorganic Semiconductors by Controlling Lattice Strain with Molecular Interactions at Surfaces

随着气候变化的加速，增加对可再生能源的依赖是必要的。一种特别有前景的可再生能源技术是基于金属卤化物钙钛矿(MHP)的光伏，它可以为商业和住宅、救灾、军事和空间应用提供轻型、低成本的电源。MHPS表现出与硅光伏等更成熟的技术类似的效率，但生产成本和浪费更低。然而，MHPS具有内在的机械和化学不稳定性，目前阻碍了商业可行性。本项目将专注于通过了解制造过程中MHPS中形成的应力如何影响性能和稳定性，以及如何通过使用有机配体(或添加剂)的定向生长或应力调节来缓解这些影响，从而解决这些不稳定性。该项目产生的基础科学知识将通过阐明可溶液处理的有机-无机杂化材料的晶格应变、稳定性和性能之间的关系来造福社会，这些材料可以用于减少材料的使用和成本，改善可再生能源的获取。同时，我们将通过亚利桑那大学现有的项目，为边缘化学生开发和举办“研究准备”研讨会。在这些研讨会上，我们还将推出一个新的视频外展试点项目--像我这样的科学家--旨在提高作为这些社区研究人员的自我概念。最后，我们将在这些相互关联的努力的基础上，为第一个此类可再生能源科学和工程辅修课程的基石课程的课程开发提供信息-这将加速将这些知识传播到我们的社区，并帮助培训更多样化的可再生能源劳动力。这个项目将利用有机分子来控制金属卤化物钙钛矿中的晶格应变，以调节这些系统的光电行为。我们将特别关注三个相互关联的问题：(1)晶格应变梯度如何影响缺陷的迁移和局部化？(2)钙钛矿型墨水中添加剂的分子结构如何影响晶体的形核、生长和取向？以及(3)添加剂的分子结构如何影响钙钛矿中的晶格应变？成功回答这些问题将是朝着实现稳定的高性能解决方案可处理设备的可扩展生产迈出的重要一步，使可再生能源、节能照明和显示器以及用于医疗保健的便携式和可穿戴传感器等低成本和变革性应用成为可能。我们将协同使用台式和计算实验来为研究途径提供信息，并朝着了解分子添加剂及其在MHP表面的相互作用如何通过应变调制影响稳定性和性能的目标迈进。此外，我们将根据一系列钙钛矿成分的特定化学成分和化学计量比，制定广泛的添加剂选择设计规则。鉴于金属卤化物钙钛矿组合物的库不断扩大，对这些广泛设计规则的需求变得越来越重要，每个组合物都有自己复杂和不同的表面化学成分。最后，我们将实施一项新战略，通过知情设计和选择分子添加剂来调节薄膜应力，以控制缺陷迁移、电荷传输和带隙，从而提高钙钛矿型器件的稳定性和性能。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。

As climate change accelerates, increased reliance on renewable energy sources is necessary. One particularly promising renewable energy technology is metal halide perovskite (MHP)-based photovoltaics, which can provide lightweight, low-cost power sources for commercial and residential, disaster relief, military, and space applications. MHPs exhibit similar efficiencies to more established technologies such as silicon photovoltaics, but with lower production cost and waste. However, MHPs have intrinsic mechanical and chemical instabilities that currently prevent commercial viability. This project will be focused on addressing these instabilities through developing an understanding of how stresses that form in the MHPs during fabrication influence performance and stability, and how these effects can be mitigated through directed growth or stress modulation by using organic ligands (or additives). The fundamental scientific knowledge produced by this project will benefit society by elucidating the relationship between lattice strain, stability, and performance in solution-processable organic-inorganic hybrid materials, which can be used to reduce the material use and cost, improving access to renewable energy. In parallel, we will develop and present “research readiness” seminars for marginalized students via established University of Arizona programs. In these seminars, we will also launch a new video outreach pilot program—Scientists Like Me—designed to increase self-concept as a researcher in these communities. Finally, we will build upon these interrelated efforts to inform curriculum development for a cornerstone course for the first of its kind Renewable Energy Science and Engineering minor—which will accelerate the dissemination of this knowledge to our communities and help train a more diverse workforce for renewable energy.This project will utilize organic molecules to control lattice strain in metal halide perovskites to modulate the optoelectronic behavior of these systems. In particular, we will focus on three interrelated questions: (1) How do lattice strain gradients influence defect migration and localization? (2) How does the molecular structure of additives in perovskite inks affect nucleation, growth, and orientation of crystallites? and (3) How can the molecular structure of additives influence lattice strains in perovskites? Successfully answering these questions will be a significant step towards realizing scalable production of stable high-performance solution-processable devices, enabling low-cost and transformative applications such as renewable energy, energy-efficient lighting and displays, and portable and wearable sensors for health care. We will synergistically use benchtop and computational experiments to inform research pathways and build towards a goal of understanding how molecular additives and their interactions at MHP surfaces can influence stability and performance through strain modulation. Furthermore, we will develop broad design rules for additive selection based on specific chemistries and stoichiometries of a range of perovskite compositions. The need for these broad design rules has become increasingly important given the ever-expanding library of metal halide perovskite compositions, each with their own complex and varied surface chemistries. Finally, we will implement a new strategy to improve the stability and performance of perovskite devices by informed design and selection of molecular additives to modulate the film stresses to control defect migration, charge transport, and band gap.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.