Correlation Between Charge Carrier Dynamics and Device Properties in Working Quasi-Two-Dimensional Perovskite Light-Emitting Diodes

近年来，钙钛矿型发光二极管(PeLED)的发展急剧放缓，并达到了瓶颈，这就需要深入了解器件的光物理及其与器件特性的关系，以指导下一代发光技术的发展。然而，由于缺乏合适的器件光物理研究技术和方法，使得现阶段对PeLED的基本工作机制尚不清楚，尤其是基于准2D钙钛矿结构的PeLED，由于多个不同维度和带隙的纳米结构的共存，导致其光电子过程复杂。为了解决这个问题，我和我的东道主主管(伦敦帝国理工学院的Artem Baklin博士和Andreas Kafizas博士)将通过建立新颖的瞬变光谱工具包(例如，电泵浦光推光探头和电泵光推光光电流测量)来研究工作准2D PeLED中的电荷载流子动力学。这些技术使我们能够在从ps到ms的时间尺度上访问工作的PeLED中的电荷注入、转移、复合和陷阱/去陷阱过程，从而为器件光物理提供了更好的洞察力。更具体地说，我们将通过控制金属氧化物电子/空穴传输层的能级和厚度来调制电荷注入和转移过程，我们将研究这两个过程如何影响器件中的电荷复合和陷阱/脱陷过程。此外，我们将把载流子动力学和耦合过程(如光子-声子和电子-声子耦合)与器件性质联系起来，以便从微观到宏观更全面地理解准2D PeLED，从而为钙钛矿型LED领域的进一步发展提供材料和器件设计的合理指导。

The development of perovskites light-emitting diodes (PeLEDs) that have great potential to be the next-generation lighting technique dramatically slows down and reaches a bottleneck in recent years, which calls for an in-depth understanding of the device photophysics and its correlation to device properties to guide the next evolution of PeLEDs. However, the lack of suitable technique and methodology for device photophysics investigation makes the fundamental working mechanism of PeLEDs remains unclear at this stage, especially for those based on quasi-2D perovskites that suffer from complicated optoelectronic processes due to the co-existence of multiple nanostructures with various dimensions and bandgaps. To address this issue, my host supervisors (Dr Artem Bakulin and Dr Andreas Kafizas from Imperial College London) and I will investigate the charge carrier dynamics in working quasi-2D PeLEDs via establishing novel transient spectroscopic toolkits (e.g., electrical pump-optical push-optical probe and electrical pump-optical push-photocurrent measurements). These techniques allow us to access the charge injection, transfer, recombination, and trapping/detrapping processes in working PeLEDs in operando with a time scale from fs to ms, and hence provide greater insight for device photophysics. More specifically, the charge injection and transfer processes will be modulated by controlling the energy level and thickness of the metal oxide electron/hole transport layer and we will study how these two processes affect charge recombination and trapping/detrapping processes in devices. Moreover, we will correlate the charge carrier dynamics and coupling processes (e.g., photon-phonon and electron-phonon coupling) with device properties to provide a more comprehensive understanding of quasi-2D PeLEDs from the microscopic to the macroscopic world, and hence offer rational guidance on the material and device designs for the further development of perovskite LED field.