Electroluminescent perovskite nanocrystals - From tailor-made assemblies to optoelectronic properties

电致发光钙钛矿纳米晶体 - 从定制组件到光电特性

• 批准号: 424708673
• 负责人: Dr. Denis Andrienko
• 金额: --
• 依托单位: Max-Planck-Institut für Polymerforschung
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/424708673?language=en
• 关键词: Electroluminescent; perovskite; nanocrystals; tailor; made

Lead halide perovskites (LHP) are well-known materials that have recently gained considerable attention in optoelectronics. Particularly LHP nanocrystals of the composition CsPbX3 (with X=Cl, Br, I) are very attractive as luminescent materials for potential applications in light-emitting diodes. They combine the advantages of bulk LHP – notably their defect tolerance, solution processability, and band-width tunability – with well-known features of colloidal quantum dots, like high photoluminescence quantum yield with narrow emission bandwidth as well as size and composition tunable colors. A fundamental problem to be addressed before the commercialization of perovskite light-emitting diodes (PeLEDs) is the poor stability of LHPs under an electric current. In conventional PeLEDs, the injection of electrons into the LHP layer leads to the irreversible formation of elemental lead and the destruction of the LHP structure. In addition, the high ion mobility in LHPs poses the problem that a significant proportion of the current in a PeLED is provided by ions, which makes no contribution to electroluminescence and has an additional destabilizing effect on the LHP structure.We address these inherent problems of PeLEDs by using organic pi-systems as surface ligands on the nanocrystals. As such, they fulfill three purposes: 1) By saturating surface defects, they increase the PLQY of the nanocrystals. 2) By inducing a surface dipole, they increase the work function of the LHP layer and thus the stability under negative charging. 3) The rigid structure in combination with the good charge carrier conductivity of the organic pi-systems suppresses ion diffusion and increases the electronic part of the total current. The project investigates the impact of this strategy on PeLEDs, covering the complete RGB color scheme and optimizing the devices in terms of external quantum efficiency, luminance and long-term stability. Computational modeling accompanies the material development and guides its optimization.

卤化铅钙钛矿(LHP)是近年来在光电子学领域备受关注的著名材料。特别是CsPbX3(X=Cl，Br，I)组成的LHP纳米晶作为发光材料在发光二极管中的潜在应用是非常有吸引力的。它们结合了块状LHP的优势--尤其是其缺陷容忍度、溶液可加工性和带宽可调整性--与胶体量子点的众所周知的特征，如发射带宽窄的高光致发光量子产率以及尺寸和组成可调的颜色。在钙钛矿型发光二极管商业化之前需要解决的一个根本问题是LHP在电流下的稳定性差。在传统的PELED中，电子注入LHP层会导致元素铅的不可逆形成和LHP结构的破坏。此外，LHP的高离子迁移率带来了这样一个问题，即在PELED中很大一部分电流是由离子提供的，这对电致发光没有贡献，并且对LHP结构有额外的不稳定作用。我们通过在纳米晶体上使用有机pi-体系作为表面配体来解决这些固有的问题。因此，它们实现了三个目的：1)通过饱和表面缺陷，它们增加了纳米晶体的PLQY。2)通过引入表面偶极子，它们增加了LHP层的功函数，从而提高了负电荷下的稳定性。3)有机Pi-体系的刚性结构与良好的载流子导电性相结合，抑制了离子扩散，增加了总电流中的电子部分。该项目研究了这一策略对PeLED的影响，涵盖了完整的RGB配色方案，并从外部量子效率、亮度和长期稳定性方面对器件进行了优化。计算建模伴随着材料的发展，指导着材料的优化。