Title:	Electronic structure of chiral hybrid organic inorganic perovskite in light emitting diodes
DNr:	LiU-compute-2022-2
Project Type:	LiU Compute
Principal Investigator:	Tianjun Liu <tl586@cam.ac.uk>
Affiliation:	Linköpings universitet
Duration:	2022-01-14 – 2023-02-01
Classification:	10304
Keywords:

Abstract

Light polarization is very important for high-contrast and efficient displays. To eliminate the glare from the external light source, circularly polarized anti-glare filters are widely applied to trap ambient light in the display. If the light source is unpolarized, half of them is blocked by the filters with decreasing brightness and efficiency. Thus, CPL is promising a candidate because it can be transmitted without the filters. Circularly polarized light (CPL) source has attracted considerable attention in many modern science and technology areas, such as optical quantum computing, data storage and encryption, and bioresponsive imaging. Normally CPL can be reproduced by incorporating a metasurface and optical elements such as quarter-wave plates. However, metasurfaces increase the system complexity and optical elements decrease efficiency. Chiral materials therefore have been potential candidates for CPL emission without an external set-up. A chiral material can exhibit optical rotation, circular dichroism and second-harmonic generation properties arising from the chirality that its mirror image cannot be brought to coincide with it. Thus, developing chiral materials for CPL devices is essential. Hybrid organic inorganic perovskites (HOIPs) have become important semiconductors for optoelectronics with advantages of tunable bandgaps, high charge mobility, low trap densities and long carrier-diffusion lengths. Attractively, perovskite light emitting diodes (PeLEDs) have been successfully demonstrated with external quantum efficiency over 20 %. Near-unity PLQY and tunable emission have enabled high performance PeLEDs spanning the visible and portions of the near-infrared spectra. Moreover, HOIPs possess a tunable organic-inorganic composition which enables the introduction of chiral ligands to form chiral perovskites. The first report of chirality in HOIPs was one-dimensional (1D) chiral perovskite single crystals in 2003. The first chiroptical study of HOIPs was performed in 2017, which made chiral perovskite revive. Since then, additional investigations of chiral perovskites have been reported, including chiral perovskite nanocrystals, nanoplates and metal-free chiral perovskites. Therefore, chiral HOIPs are promising candidates for CPL sources.