Nanoscale photophysics at defects and interfaces in organic semiconductors

有机半导体缺陷和界面的纳米光物理

• 批准号: EP/V044907/1
• 负责人: Sean Collins
• 金额: $ 52.67万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FV044907%2F1
• 关键词: Nanoscale; photophysics; defects; interfaces; organic

The success of silicon electronics hinged on the production of high-purity, near-perfect crystals of silicon with well-controlled properties at the boundary (or interface) between different components of a micro-chip. Today, the search is well underway for materials that will serve analogous or additional functions but that achieve top performance while also being flexible, light-weight, easily processed, and mechanically durable. These desirable properties are most typically found in materials built in whole or part from molecules incorporating carbon-carbon bonds. Many of these materials, based on organic semiconductors, are already on the market in screens and sensors. And yet little is understood about the exact role played by imperfections in these materials. Very small imperfections, or defects, stop the movement of charges in these materials, and it is this controlled movement of charge that governs how well they work.The ability to pinpoint tiny imperfections requires substantial advances in electron microscopy, the tool used to directly measure materials structure down to the positions of individual atoms. At the moment, most research relies on measurements that describe only the average position of where molecules and atoms are inside an organic semiconductor. It can sometimes be inferred that targeted properties like light emission or light absorption are better or worse as a result of disorder and defects that are present. But only by seeing defects directly and measuring how they behave at the appropriate length scale can they be understood fully. Identifying where the molecules and atoms are in a material is a large part, but only a part, of the full story. The missing piece is the direct experimental observation of 'how' and 'why' particular defects govern how efficiently a semiconductor emits or absorbs light. This interaction with light then determines how well a display screen works or how long a wearable light-based sensor will last.These 'how' and 'why' questions depend fundamentally on the energy landscape created by defects; electrons will roll downhill. Electrons travelling through a material may run into an insurmountable obstacle if they encounter a region of material that is 'uphill' or at higher energy. Microscopy using electron beams is a mainstay technique for seeing 'where' and 'what' is happening in the landscape at the dimension of single atoms. The challenge is that organic semiconductors are easily damaged by electron beams. This research programme will create innovative approaches, including the use of machine learning and data science techniques as well as new microscope hardware, for using electrons beams to measure the energy landscape of organic semiconductors.First, the optical properties - how a material absorbs or scatters light - will be examined at the small 'uphill' defects in organic semiconductors used in light emitting diodes (LEDs). With cutting edge electron microscopes, it is now possible to directly see how a material absorbs or emits light at visible light energies. The physics associated with these electron beam interactions means these measurements can also be carried out in a way that avoids damaging the sample beyond recognition. Next, the positions of individual atoms in molecular materials will be analysed. At defective regions in a material, individual atoms are misplaced from their expected positions. In this work, where the atoms sit at these mistakes will be measured very precisely and compared with observations about how 'uphill' or 'downhill' the landscape is in the vicinity. In the final stage, the new tools will be extended to look inside fully operational devices consisting of many layers. By cutting out cross-sections from these multi-layered devices, the new insights from electron microscopy, ultimately, will be integrated with processes in use on manufacturing development and quality control platforms.

硅电子器件的成功取决于高纯度、近乎完美的硅晶体的生产，并且微芯片不同组件之间的边界（或界面）具有良好控制的特性。如今，人们正在积极寻找能够提供类似或附加功能但能实现顶级性能，同时还具有灵活性、重量轻、易于加工和机械耐用的材料。这些理想的特性最常见于全部或部分由结合碳-碳键的分子构建的材料。其中许多基于有机半导体的材料已经在市场上用于屏幕和传感器。然而，人们对这些材料中的缺陷所起的确切作用却知之甚少。非常小的缺陷或缺陷会阻止这些材料中的电荷运动，正是这种受控的电荷运动决定了它们的工作效果。精确定位微小缺陷的能力需要电子显微镜的重大进步，电子显微镜是用于直接测量材料结构直至单个原子位置的工具。目前，大多数研究依赖于仅描述有机半导体内部分子和原子的平均位置的测量。有时可以推断，由于存在的无序和缺陷，目标特性（如光发射或光吸收）变得更好或更差。但只有直接观察缺陷并测量它们在适当长度范围内的表现才能完全理解它们。识别材料中分子和原子的位置是整个故事的很大一部分，但只是一部分。缺失的部分是对特定缺陷“如何”以及“为何”控制半导体发射或吸收光的效率的直接实验观察。这种与光的相互作用决定了显示屏的工作效果或可穿戴光传感器的使用寿命。这些“如何”和“为什么”问题从根本上取决于缺陷所产生的能量景观；电子会滚下坡。如果电子穿过材料时遇到“上坡”或能量较高的材料区域，则可能会遇到难以逾越的障碍。使用电子束显微镜是一种主要技术，可以在单个原子的维度上观察景观中“何处”和“发生了什么”。挑战在于有机半导体很容易被电子束损坏。该研究计划将创建创新方法，包括使用机器学习和数据科学技术以及新的显微镜硬件，以使用电子束测量有机半导体的能量景观。首先，将在发光二极管（LED）中使用的有机半导体的微小“上坡”缺陷上检查光学特性（材料如何吸收或散射光）。借助最先进的电子显微镜，现在可以直接观察材料如何吸收或发射可见光能量的光。与这些电子束相互作用相关的物理原理意味着这些测量也可以避免对样品造成无法识别的损坏。接下来，将分析分子材料中单个原子的位置。在材料的缺陷区域，单个原子会偏离其预期位置。在这项工作中，将非常精确地测量原子在这些错误处的位置，并与附近景观“上坡”或“下坡”的观察结果进行比较。在最后阶段，新工具将扩展到查看由多层组成的完全可操作的设备的内部。通过从这些多层设备中切出横截面，电子显微镜的新见解最终将与制造开发和质量控制平台上使用的流程相集成。

项目成果

Interfacial alloying between lead halide perovskite crystals and hybrid glasses.

• DOI: 10.1038/s41467-023-43247-6
• 发表时间: 2023-11-22
• 期刊: NATURE COMMUNICATIONS
• 影响因子: 16.6
• 作者: Li, Xuemei;Huang, Wengang;Krajnc, Andraz;Yang, Yuwei;Shukla, Atul;Lee, Jaeho;Ghasemi, Mehri;Martens, Isaac;Chan, Bun;Appadoo, Dominique;Chen, Peng;Wen, Xiaoming;Steele, Julian A.;Hackbarth, Haira G.;Sun, Qiang;Mali, Gregor;Lin, Rijia;Bedford, Nicholas M.;Chen, Vicki;Cheetham, Anthony K.;Tizei, Luiz H. G.;Collins, Sean M.;Wang, Lianzhou;Hou, Jingwei
• 通讯作者: Hou, Jingwei

Mapping nanocrystalline disorder within an amorphous metal-organic framework.

• DOI: 10.1038/s42004-023-00891-9
• 发表时间: 2023-05-11
• 期刊: Communications chemistry
• 影响因子: 5.9
• 作者: Sapnik AF;Sun C;Laulainen JEM;Johnstone DN;Brydson R;Johnson T;Midgley PA;Bennett TD;Collins SM
• 通讯作者: Collins SM

Tribo-induced catalytically active oxide surfaces enabling the formation of the durable and high-performance carbon-based tribofilms

• DOI: 10.1016/j.triboint.2023.108476
• 发表时间: 2023-06
• 期刊: Tribology International
• 影响因子: 6.2
• 作者: Kim Khai Huynh;S. Pham;A. Tieu;S. Collins;Cheng Lu;Shanhong Wan