NSF/CBET-BSF: Effect of Sunlight Intensity on Functional Inhomogeneity and Stability of Organic-Inorganic Perovskite Solar Cells

太阳是地球上最丰富的潜在可持续能源。用于发电的太阳能电池需要吸收太阳能量并将其光子转化为电子的材料，这一过程被称为光伏。最近，基于无机-有机卤化物钙钛矿材料的材料已经取得了接近硅太阳能电池的良好的太阳能转换效率，并且可以利用富含地球的元素以较低的成本、基于溶液的制备方法来制备。然而，目前的有机-无机钙钛矿型光伏器件在高阳光和空气湿度的长期使用过程中会发生化学降解。此外，现有的制造方法导致最终器件的性能不一致。该项目的目标是开发新的制造方法，以提高钙钛矿型光伏器件的环境稳定性和性能重复性，以帮助其未来的实际应用。该项目的一个独特之处在于，这项研究将作为美国麻省理工学院和以色列内盖夫本古里安大学之间正式国际合作的一部分进行。这两个机构都提供了独特的和免费的研究专业知识以及学生培训的机会。该研究计划将寻求通过四种材料制备策略来提高钙钛矿型光伏器件的环境稳定性和制造重复性：1)在有源层中引入具有特殊功能的分子物种，2)调整成膜动力学，3)调节光活性薄膜的化学成分，以及4)添加降低电荷陷阱密度的钝化剂。这些战略将在三个研究目标的范围内进行调查。第一个目标是从根本上理解甲基铵三碘化铅电子性质中颗粒到颗粒的变异性的起源。第二个目标是阐明微尺度辐射中非辐射衰变的起源。作为这一目标的一部分，晶体结构和组成将与微尺度上的特征发光和电子性质相关联。第三个目标是确定限制甲基铵三碘化铅的重现性和环境稳定性的因素，特别侧重于确定导致光伏恶化的机制，这种恶化限制了在集中阳光下运行设备的稳定性。

The sun represents the most abundant potential source of sustainable energy on earth. Solar cells for producing electricity require materials that absorb the sun's energy and convert its photons to electrons, a process called photovoltaics. Recently, materials based on inorganic-organic halide perovskite materials have achieved promising solar energy power conversion efficiency approaching that of silicon solar cells, and can be made from earth-abundant elements using lower-cost, solution based fabrication methods. However, present organic-inorganic perovskite photovoltaic devices chemically degrade during long-term service under both high sunlight and moisture in air. Furthermore, present methods for their fabrication result in the inconsistent performance of the final device. The goal of this project is to develop new fabrication methods to improve the environmental stability and performance reproducibility of perovskite-based photovoltaic devices to help enable their future practical use. A unique aspect of this project is that the research will be carried out as part of a formal international collaboration between the Massachusetts Institute of Technology in the United States and the Ben-Gurion University of the Negev in Israel. Both institutions bring unique and complimentary research expertise as well as opportunities for student training. The research plan will seek to improve environmental stability and fabrication reproducibility of perovskite-based photovoltaic devices through four material fabrication strategies: 1) introduce molecular species with specialized functionality into the active layer, 2) adjust film formation kinetics, 3) tune the chemical composition of photoactive films, and 4) add passivating agents that reduce charge trap densities. These strategies will be investigated within the context of three research objectives. The first objective is to develop a fundamental understanding the origin of the grain-to grain variability in electronic properties of methylammonium lead triiodide. The second objective is to elucidate the origin of non-radiative decay in the microscale emission. As part of this objective, the crystallographic structure and composition will be correlated to characteristic luminescence emission and electronic properties at the microscale. The third objective is to determine the factors limiting the reproducibility and environmental stability of methylammonium lead triiodide, with particular focus on identifying the mechanisms responsible for photovoltaic deterioration that limits operational device stability under concentrated sunlight.