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

非技术性：太阳能是最有前途的绿色技术之一，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、低成本和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功率转换效率已经见证了前所未有的增长率。尽管它们具有出色的性能，但钙钛矿具有差的稳定性，并且由于离子迁移而易于光分解。它们的环境兼容性也存在严重问题，因为性能最高的钙钛矿太阳能电池含有铅，这是一种剧毒金属。此外，碘化铅是这些材料的常见分解产物，具有致癌性。面对这些挑战，有必要识别和开发在光照射下和暴露于环境时本质上稳定的高性能无铅钙钛矿。这个项目将研究基于硫属钙钛矿的太阳能电池，硫属钙钛矿是太阳能电池中常用的金属卤化物钙钛矿的替代品。这些材料不含铅，并使用硫族元素，如硫，这可能导致上级稳定性。该项目可能会导致一类新的高性能和环境稳定的太阳能电池和光电探测器的变革性的影响。技术：一些基础科学和器件工程问题将在这个项目中得到解决，以使硫属钙钛矿基材料的高性能光电器件，如光电探测器和太阳能电池的成功部署。其中包括：（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、中间带隙状态和载流子寿命。硫族化物钙钛矿材料的生长条件将被仔细控制，以尽量减少这种缺陷;（2）合金化策略，以优化硫族化物钙钛矿基材料的带隙将在理论上预测使用第一性原理密度泛函理论计算。这种合金化也将在实验上实现，以证明具有优化带隙的硫属化物钙钛矿材料;（3）最先进的机器学习工具（由从头计算和实验指导）将用于系统地筛选整个硫属钙钛矿材料家族，以找到最佳材料和合金化组合;（4）将开发使用优化的硫族化物钙钛矿材料构造的光电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，以证明高性能，环境稳定和无铅光电器件使用的硫族钙钛矿材料的家庭。该奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

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.