Design Rules for Obtaining White Light from Layered Perovskites and Related Lattices

第1部分：非技术总结预计到2025年，向固态照明(SSL)的过渡将使全球照明用电量减半。SSL设备使用涂有荧光粉材料的发光二极管(LED)，将LED中的蓝光或紫外光转换为白光。发射的光必须覆盖整个可见光谱，类似于太阳光，才能使照明准确地显示被照明对象的颜色。然而，具有如此宽带发射的荧光粉是非常罕见的。商业SSL设备将不同颜色的LED和荧光粉混合在一起，以获得宽带白光，但对于人工照明来说，发射宽带白光的单一材料是非常理想的。层状杂化钙钛矿是一种晶态材料，含有交替的有机和无机层。某些层状金属卤化物钙钛矿的无机层可以将紫外光转换为宽带白光。这项拟议的工作得到了材料研究部固态和材料化学以及电子和光子材料计划的支持，旨在将白光发射扩大到更大范围的晶格。尤其是无毒成分，将成为目标。迄今为止，新的白光金属卤化物的发现仍然是偶然的。这项研究将确定和传播白光发射体的可预测合成的设计规则。本科生研究人员将参与研究的方方面面。一门新课程将使用材料化学中的例子向一年级学生介绍一般化学概念。固体和无机化学的概念，通常不包括在一年级的课程中，将在普通化学中引入，以吸引学生尽早接触这些领域。在当地高中和斯坦福大学的外联活动也将强调材料发现的重要性，演示包括在PI的小组中合成新材料。第2部分：技术总结从没有离散生色团的单一材料发出宽带白光是非常不寻常的。2D杂化卤化物钙钛矿的无机层已经报道了这样的发射，归因于激子自捕获。尽管现在有越来越多的金属卤化物宽带发射体被报道，但它们仍然是相对罕见的孤立例子，受到偶然发现的推动。这项研究得到了材料研究部固态和材料化学以及电子和光子材料计划的支持，旨在探索激子在大范围晶格中自捕获的共性，以大幅增加本征白光发射器的数量。对具有不同组成和连通性的0D、1D和2D晶格的合成和光学研究将允许阐明合理合成白光发射体的总体设计规则。稳态和时间分辨光谱仪将探索晶格的基态结构和与自陷相关的激发态扭曲之间的关联。这些方法还将通过研究自然和化学诱导的晶格缺陷对发射的影响来探讨外在自陷的作用。这里概述的基础研究有望为合成能够以可预测的方式操纵光的材料奠定基础。单源白光发射器通过混合多个不同的荧光粉或发光二极管，消除了与当前产生白光的方法相关的问题。与无机荧光粉和有机LED相比，这些混合材料的发光机制完全不同，这可能会为它们在大面积显示器和面板中的使用开辟新的利基市场。本科生研究人员将参与研究的方方面面。为该项目合成的新材料将包括在高中外展活动中。一门新课程将使用材料化学中的例子向一年级学生介绍一般化学概念。固体和无机化学的概念通常不包括在第一年的课程中，为了吸引学生早日进入这些领域，将在普通化学中引入这些概念。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。

PART 1: NON-TECHNICAL SUMMARYThe transition to solid-state lighting (SSL) is predicted to halve global electricity consumption for lighting by the year 2025. SSL devices use light-emitting diodes (LEDs) coated with a phosphor material, which converts blue or ultraviolet light from the LED to white light. The emitted light must span the entire visible spectrum, similar to sunlight, in order for the lighting to accurately show the colors of illuminated objects. However, phosphors with such broadband emission are very rare. Commercial SSL devices mix LEDs and phosphors of different colors to achieve broadband white light, but a single material that emits broadband white light is highly desirable for artificial illumination. Layered hybrid perovskites are crystalline materials that contain alternating organic and inorganic layers. The inorganic layers of some layered metal-halide perovskites can convert ultraviolet light to broadband white light. The proposed work, supported by the Solid State and Materials Chemistry and Electronic and Photonic Materials programs in the Division of Materials Research, seeks to expand white-light emission to a much larger range of lattices. Nontoxic compositions, in particular, will be targeted. To date, the discovery of new white-light-emitting metal halides remains serendipitous. This research will identify and disseminate design rules for the predictable synthesis of white-light emitters. Undergraduate researchers will be involved in all aspects of the research. A new course will introduce general chemistry concepts to first-year students using examples from materials chemistry. Concepts in solid state and inorganic chemistry, which are typically not included in first-year courses, will be introduced in general chemistry in order to draw students to these fields early. Outreach activities at local high schools and at Stanford University will also emphasize the importance of materials discovery, with demonstrations including new materials synthesized in the PI's group. PART 2: TECHNICAL SUMMARYBroadband white-light emission from a single material without discrete chromophores is extremely unusual. Such an emission has been reported from the inorganic layers of 2D hybrid halide perovskites, attributed to exciton self-trapping. Although a growing number of metal-halide broadband emitters are now being reported, they remain as relatively rare, isolated examples driven by serendipitous discovery. This research, supported by the Solid State and Materials Chemistry and Electronic and Photonic Materials programs in the Division of Materials Research, seeks to probe the generality of exciton self-trapping in a large range of lattices to substantially increase the number of intrinsic white-light emitters. Synthetic and optical studies of 0D, 1D, and 2D lattices with varying composition and connectivity will allow for the articulation of overarching design rules for the rational synthesis of white-light emitters. Steady-state and time-resolved spectroscopies will probe correlations between the ground-state structure of the lattices and excited-state distortions associated with self-trapping. These methods will also interrogate the role of extrinsic self-trapping by studying the influence of native and chemically induced lattice defects on the emission. The fundamental studies outlined here are expected to set the stage for the synthesis of materials that can manipulate light in a predictable manner. Single-source white-light emitters eliminate problems associated with current methods of producing white light by mixing multiple different phosphors or light-emitting diodes. The fundamentally different emission mechanism in these hybrids compared to those of inorganic phosphors and organic LEDS may open new niches for their use in large-area displays and panels. Undergraduate researchers will be involved in all aspects of the research. New materials synthesized for this project will be included in high school outreach events. A new course will introduce general chemistry concepts to first-year students using examples from materials chemistry. Concepts in solid state and inorganic chemistry, which are typically not included in first-year courses, will be introduced in general chemistry in order to draw students to these fields early.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.