Collaborative Research: Fundamental Study of Environmentally Stable and Lead-Free Chalcogenide Perovskites for Optoelectronic Device Engineering

非技术性：太阳能是最有前景的绿色技术之一，可以使人类以可持续的方式满足未来的能源需求。因此，开发高性能、低成本、环保的太阳能电池对我们的能源安全至关重要。金属卤化物钙钛矿是最有前途的新型太阳能材料之一。由这种钙钛矿制成的太阳能电池的电能转换效率出现了前所未有的提高。尽管钙钛矿具有优异的性能，但其稳定性较差，并且由于离子迁移而容易光解。它们的环境兼容性也存在严重问题，因为性能最好的钙钛矿型太阳能电池含有剧毒金属铅。此外，这些物质的常见分解产物碘化铅是致癌的。面对这些挑战，有必要确定和开发高性能和无铅的钙钛矿材料，这些材料在光照射下和暴露在环境中时本质上是稳定的。该项目将研究基于硫化物钙钛矿的太阳能电池--一种通常用于太阳能电池的金属卤化物钙钛矿的替代品。这些材料不含铅，并使用硫磺等硫化物，这可能会导致优异的稳定性。技术：该项目将解决一些基础科学和器件工程问题，以使硫系钙钛矿型材料能够成功地应用于高性能光电器件，如光电探测器和太阳能电池。这些内容包括：(1)了解这些材料中缺陷的性质，以及它们如何影响暗电流、能带结构、中间能隙状态和载流子寿命。将仔细控制硫系钙钛矿材料的生长条件，以最大限度地减少此类缺陷；(2)利用第一性原理密度泛函理论计算，从理论上预测了优化硫系钙钛矿基材料带隙的合金化策略。这种合金化也将在实验上实现，以展示具有优化带隙的硫系钙钛矿材料；(3)将使用最先进的机器学习工具(在从头计算和实验指导下)来系统筛选整个硫系钙钛矿材料家族，以找到最佳材料和合金化组合；(4)将开发使用优化的硫系钙钛矿材料构建的光探测器和太阳能电池器件，并对其进行系统表征，以证明概念的证明。上述任务将共同提供所需的基础知识，以展示使用硫系钙钛矿材料系列的高性能、环境稳定和无铅的光电设备。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:Solar energy is one of the most promising green technologies and could enable humankind to meet its future energy needs in a sustainable manner. The development of high performance, low cost and environmentally friendly solar cells is therefore critical for our energy security. One of the most promising new class of materials for solar energy is metal halide perovskites. The power conversion efficiency of solar cells made from such perovskites has witnessed an unprecedented rate of increase. Despite their outstanding performance, perovskites have poor stability and are prone to photo-decomposition due to ion migration. There are also serious issues with their environmental compatibility as the highest performing perovskite solar cells contain lead, a highly poisonous metal. Furthermore, lead iodide, a common decomposition product of these materials, is carcinogenic. In the face of these challenges, it is necessary to identify and develop high performing and lead free perovskites that are intrinsically stable under light irradiation and when exposed to the environment. This project will investigate solar cells based on chalcogenide perovskites—an alternative to metal halide perovskites typically used in solar cells. These materials are free of lead and use a chalcogen such as sulfur, which could result in superior stability. This project could lead to a new class of high performance and environmentally stable solar cells and photodetectors with transformative impacts.Technical:A number of fundamental science and device engineering issues will be addressed in this project in order to enable the successful deployment of chalcogenide perovskite based materials in high performing optoelectronic devices such as photo-detectors and solar cells. These include: (1) understanding the nature of defects in these materials, and how they affect the dark current, band structure, mid gap states, and carrier lifetimes. The chalcogenide perovskite material growth conditions will be carefully controlled, to minimize such defects; (2) Alloying strategies to optimize the band gap of chalcogenide perovskite based materials will be theoretically predicted using first-principles density functional theory calculations. Such alloying will also be experimentally realized to demonstrate chalcogenide perovskite materials with optimized bandgaps; (3) State of the art machine learning tools (guided by ab initio calculations and experiments) will be used to systematically screen the entire family of chalcogenide perovskite materials in order to find the optimal material and alloying combination; (4) Photo-detector and solar cell devices constructed using the optimized chalcogenide perovskite material will be developed and systematically characterized to demonstrate the proof of concept. The above tasks will together provide the fundamental knowledge that is needed to demonstrate high performing, environmentally stable and lead free optoelectronic devices using the family of chalcogenide perovskite materials.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.