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

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.