Microscopic understanding of the phonon bottleneck in 2D perovskites

二维钙钛矿中声子瓶颈的微观理解

• 批准号: 504846924
• 负责人: Professor Dr. Ermin Malic
• 金额: --
• 依托单位: Faculty of Fundamental Problems of Technology
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/504846924?language=en
• 关键词: Microscopic; understanding; phonon; bottleneck; 2D

Perovskites constitute a remakable semiconducting material system, which is in many aspects very different from the well-known and understood family of epitaxial semiconductors. The huge interest in 3D perovskites triggered an investigation of their lower dimensional forms, such as nanocrystals and two-dimensional (2D) perovskites. The latter are known for their superior emissive properties exhibiting a quantum emission efficiency that is one or two orders of magnitude higher than in conventional semiconductors. The microscopic origin of this technologically important characteristics is still the subject of ongoing research and has been controversially discussed in literature. The soft lattice results in a specific exciton-phonon interaction in perovskite materials, in particular, excitons are known to a couple very weakly to acoustic phonons. It was proposed that this leads to extremely reduced phonon assisted scattering into the dark exciton states explaining very intense luminescence from perovskites nanocrystals. However, a clear evidence for this phonon bottleneck between bright and dark exciton states in 2D perovskites is still missing and an advanced microscopic modelling of exciton relaxation dynamics is needed. In this joint experiment-theory project, we will investigate the microscopic origin of the phonon bottleneck in 2D perovskites and its impact on their optical properties. These technologically promising nanomaterials constitute an unprecedented playground to study the phonon bottleneck between bright and dark exciton states as they offer the possibility for independent modification of the excitonic fine structure and the phonon spectrum. This provides an opportunity not only to thoroughly understand phonon-mediated exciton relaxation, but also to control and overcome the phonon bottleneck for a deterministic design of novel highly efficient light emitters. By varying the 2D perovskite quantum well thickness, chemical composition and organic spacer molecule we will be able to tune the spectral difference between the dark-bright exciton splitting and the optical phonon energy revealing the conditions for enhanced or suppressed phonon bottleneck effect. To realize the general objective of this project we will join forces of experimental and theoretical groups. Merging expertise in the field of optical spectroscopy with advanced exciton dynamics modelling we will provide microscopic insights into the elementary processes behind the phonon-bottleneck in 2D perovskites and we will reveal strategies of how to control this effect and optimize the technologically crucial quantum emission efficiency of 2D perovskites.

钙钛矿构成了一个可改造的半导体材料体系，它在许多方面与众所周知的外延半导体家族有很大的不同。对三维钙钛矿的巨大兴趣引发了对其低维形式的研究，如纳米晶体和二维钙钛矿。后者以其优越的发射特性而闻名，其量子发射效率比传统半导体高一到两个数量级。这一技术上重要特征的微观起源仍然是正在进行研究的主题，并在文献中进行了有争议的讨论。软晶格导致钙钛矿材料中特定的激子-声子相互作用，特别是激子与声子的相互作用非常弱。有人提出，这导致声子辅助散射到暗激子态的极大减少，解释了钙钛矿纳米晶体非常强烈的发光。然而，二维钙钛矿中明暗激子状态之间的声子瓶颈仍然缺乏明确的证据，并且需要一个先进的激子弛缓动力学的微观模型。在这个联合实验理论项目中，我们将研究二维钙钛矿中声子瓶颈的微观起源及其对其光学性质的影响。这些技术上有前景的纳米材料为研究明亮和黑暗激子状态之间的声子瓶颈提供了前所未有的平台，因为它们为激子精细结构和声子谱的独立修改提供了可能性。这不仅为彻底理解声子介导的激子弛豫提供了机会，而且为新型高效光发射器的确定性设计提供了控制和克服声子瓶颈的机会。通过改变二维钙钛矿量子阱厚度、化学成分和有机间隔分子，我们将能够调整暗-亮激子分裂和光声子能量之间的光谱差异，揭示声子瓶颈效应增强或抑制的条件。为了实现这个项目的总体目标，我们将结合实验和理论小组的力量。将光谱学领域的专业知识与先进的激子动力学建模相结合，我们将提供二维钙钛矿中声子瓶颈背后的基本过程的微观见解，我们将揭示如何控制这种影响并优化技术上至关重要的二维钙钛矿量子发射效率的策略。