Manipulating the Transition Dipole Moment of CsPbBr₃ Perovskite Nanocrystals for Superior Optical Properties

Abstract

Colloidal cesium lead halide perovskite nanocrystals exhibit unique photophysical properties including high quantum yields, tunable emission colors, and narrow photoluminescence spectra that have marked them as promising light emitters for applications in diverse photonic devices. Randomly oriented transition dipole moments have limited the light outcoupling efficiency of all isotropic light sources, including perovskites. In this report we design and synthesize deep blue emitting, quantum confined, perovskite nanoplates and analyze their optical properties by combining angular emission measurements with back focal plane imaging and correlating the results with physical characterization. By reducing the dimensions of the nanocrystals and depositing them face down onto a substrate by spin coating, we orient the average transition dipole moment of films into the plane of the substrate and improve the emission properties for light emitting applications. We then exploit the sensitivity of the perovskite electronic transitions to the dielectric environment at the interface between the crystal and their surroundings to reduce the angle between the average transition dipole moment and the surface to only 14°and maximize potential light emission efficiency. This tunability of the electronic transition that governs light emission in perovskites is unique and, coupled with their excellent photophysical properties, introduces a valuable method to extend the efficiencies and applications of perovskite based photonic devices beyond those based on current materials.

Efficient interlayer exciton transport in two-dimensional metal-halide perovskites

“…The strong polarization is consistent with a strong IP orientation of the transition dipole of the excitons. [39][40][41] To gain qualitative insight in the exciton transport along the IP and OP directions of the crystal, we look at the photoluminescence emission profile following near-diffraction-limited excitation (λex = 405 nm, FWHM = 250 nm). While the excitation profile is fully symmetric, we observe a distinctly asymmetric emission profile on the ac crystal plane that is elongated along the IP direction (see Figure 1D).…”

Scalable photonic sources using two-dimensional lead halide perovskite superlattices

“…B right excitons in quantum-confined two-dimensional (2D) materials have their transition dipole moment (TDM) oriented in parallel to the surface plane [1][2][3][4] , which is essential to enable high-efficiency quantum optics 5,6 and electroluminescent devices 7,8 . It is desirable to fabricate the decoupled multi-quantumwell (MQW) superlattices 3 by inserting atomically thin quantum barriers (QBs) between individual 2D material layers 9 .…”

“…Since the quantum emission characteristics are mediated by the TDMs that orthogonally interact with the electromagnetic fields of the emitted photons, the dipole orientation of bright excitons in 2D materials is predominantly in-plane (IP) [1][2][3][4] , analogous to those in the planar molecules 7 . When interlayer coupling comes into play, the symmetry is broken and the outof-plane (OP) components are induced 23,25 .…”

Effect of mixed halide contents on structural, electronic, optical and elastic properties of CsSnI3−xBrx for solar cell applications: first-principles study

“…It is clear from the band structure diagrams in figure 3 that band gap is increased when we replace the I atoms by Br atoms due to decrease in atomic size. This is due to fact that as the I has the more number of nucleons than Br atom, so the I, due to its large size have the less electrostatic force of attraction between nucleus and the outermost electrons (shielding [21]. b [22].…”