DMREF: SusChEM: Simulation-Based Predictive Design of All-Organic Phosphorescent Light-Emitting Molecular Materials

DMREF: SUSCHEM：基于仿真的全有机磷光发光分子材料预测设计非技术描述：有机发光二极管（OLED）在从城市照明到大屏幕显示面板的应用中表现出卓越的能源效率。目前的技术是基于含有有机金属化合物的磷光材料，其中涉及重金属离子。这些材料价格昂贵，设备寿命有限，在某些情况下被认为对环境不安全，甚至有毒。这项研究的目标是通过开发一种全新的全有机磷光分子来消除对重金属离子的需求。主要任务是设计分子，其中电子轨道的并列促进了磷光的过程，同时化学键模式提供了最小化电子激发的非辐射衰变所需的结构刚度。为此，采用了综合计算实验方法，其中分子模拟，化学合成和材料表征以协同和迭代的顺序结合在一起。该项目的预期成果是基于可持续化学的新型环保磷光材料，并可立即用于照明应用。在完善无金属OLED的同时，获得了对分子材料功能响应的新见解，这有利于有机电子产品的整体发展，以及光伏、传感器和显示器等先进技术的发展。最后，建立了基于模拟的预测性材料设计的软件工具包、数据管理实用程序和工作流程，作为材料开发的新范例。技术描述：磷光材料的效率不仅是基于单线态发射的能力，也基于三重态发射的能力，这是自旋轨道耦合的结果。这种耦合的强度归因于有机金属化合物中重金属离子的存在。然而，有机金属材料也面临着巨大的挑战：除了贵金属的高成本外，发射层中错位的金属离子可能会捕获电荷，从而危及器件的寿命。巧合的是，co-PI证明了无金属有机荧光粉在环境条件下具有前所未有的高固态磷光量子产率高达68%。目前的研究旨在进一步开发这种全新的、环境友好的、化学可持续的全有机磷光分子，并采用综合计算-实验方法改善其性能特征。具体目标是：(i)消除发射分子中的重金属离子，以降低材料成本和可获得性，提高制造的便利性，延长设备的使用寿命和可靠性；（ii）消除卤素键促进自旋轨道耦合和抑制振动能量耗散的双重作用，用分子内类似物取代分子间二级键诱导的磷光增强机制；（iii）优化发射体和寄主体的分子结构，通过加强分子内键模式，稳定寄主分子以抑制有效填充几何结构中的有害振动，以及在纳米限制下使发射体结晶，从而最大限度地减少振动介导的激发态的非辐射衰变。为此，构建了概念发射器和宿主分子，并利用第一性原理计算预测了它们的结构和电子性质，如激发态能、单重态-三重态跃迁速率、电荷迁移率等。使用形状填充算法和分子模拟生成结构模型，并预测可能的晶体结构。合成最佳候选分子，对其进行表征，并测量其发射和振动特性。

DMREF: SUSCHEM: SIMULATION-BASED PREDICTIVE DESIGN OF ALL-ORGANIC PHOSPHORESCENT LIGHT-EMITTING MOLECULAR MATERIALSNon-technical Description: Organic light emitting diodes (OLED) exhibit remarkable energy efficiency in applications ranging from urban lighting to large-screen display panels. Current technologies are based on phosphorescent materials that contain organo-metallic compounds, which involve heavy-metal ions. These are expensive to procure, present limitations with regard to device longevity, and in some cases are considered environmentally unsafe or even toxic. The goal of this research is to eliminate the need for heavy-metal ions by developing a fundamentally new class of all-organic phosphorescent molecules. The principal task is to design molecules in which the juxtaposition of electronic orbitals promotes the processes underlying phosphorescence while at the same time the chemical bonding patterns provide the structural rigidity needed to minimize the non-radiative decay of electronic excitations. To this end an integrative computational-experimental approach is employed, in which molecular simulations, chemical synthesis, and materials characterization are combined in a synergistic and iterative sequence. The expected outcomes of this project are novel environmentally benign phosphorescent materials that are based on sustainable chemistries and that are immediately deployable for lighting applications. The new insights into the functional response of molecular materials gained while perfecting metal-free OLED benefits organic electronics in general, and advance technologies such as photovoltaics, sensors, and displays. Finally, software toolkits, data management utilities, and workflows for simulation-based predictive materials design are established as a new paradigm for materials development.Technical Description: The efficiency of phosphorescent materials is based on the ability to emit not only from singlet but also triplet excited states, which are populated as a result of spin-orbit coupling. The strength of this coupling is attributed to the presence of heavy-metal ions in organo-metallic compounds. However, organo-metallics are accompanied by significant challenges: besides the high cost of precious metals, dislocated metal ions in the emitting layer may trap charge, which jeopardizes device longevity. By serendipity, the co-PI demonstrated metal-free organic phosphors with unprecedented high solid-state phosphorescent quantum yield of up to 68% at ambient conditions. The current research aims to further develop this fundamentally new, environmentally benign, and chemically sustainable class of all-organic phosphorescent molecules with improved performance characteristics by employing an integrated computational-experimental approach. Specific objectives are to (i) eliminate the heavy metal ions form the emitting molecules with the aim to lower materials cost and obtainability, improve ease of fabrication, and prolong device lifetime and dependability; (ii) deconvolute the dual roles of halogen bonding, i.e., to promote spin-orbit coupling and suppress vibrational energy dissipation, and supplant the intermolecular secondary bonding-induced phosphorescence enhancement mechanism with intramolecular analogs; (iii) optimize the molecular architectures of both the emitting and host species so as to minimize vibration-mediated non-radiative decay of excited states through stiffening of intramolecular bonding patterns, stabilization of emitters by host molecules designed to suppress detrimental vibrations within effectively packed geometries, and crystallization of emitters within nano-confinement. To this end, concept emitter and host molecules are constructed and their structure and electronic properties, e.g., excited state energies, singlet-triplet transition rates, charge mobilities, etc., predicted using first-principles calculations. Structural models are generated using shape packing algorithms and molecular simulations, and possible crystal structures are predicted. Best candidate molecules are synthesized, characterized, and their emissive and vibrational properties measured.