Quantum Confinement and Dielectric Deconfinement in Quasi-Two-Dimensional Perovskites: Their Roles in Light-Emitting Diodes

In quasi-two-dimensional (quasi-2D) perovskites, inorganic quantum wells are sandwiched between organic spacers (barriers) from the energy-level perspective. In addition to quantum confinement, dielectric confinement occurs in the layered perovskites due to a large difference in the dielectric constants of the inorganic framework and the organic spacer layer. While quantum confinement increases the exciton binding energy, deconfinement in the dielectric constant results in a decrease in exciton binding energy and also an increase in carrier mobility. In this work, we investigate the effects of quantum confinement and dielectric deconfinement on the dynamic response of light-emitting diodes (LEDs) based on several series of quasi-2D perovskites and operated under an alternating voltage. With pulsed electroluminescence emission appearing in both bias sections of sinusoidal ac voltages, we show how the quantum confinement and dielectric deconfinement affect and increase the frequency range of ac LED operation, that is, the \ensuremath{-}3 dB cutoff frequency. This \ensuremath{-}3-dB frequency could be seen to increase due to a relaxation of quantum and dielectric confinements, leading to an enhancement of the effective carrier mobility in the active emitting material of the devices.