A new methodology to analyze the kinetics that determine the light emission in voltage-driven devices is presented. It consists of combining the voltage-modulated light emission with impedance spectroscopy, whose spectra are interpreted according to the described equivalent circuit. This method, which is unprecedently applied to perovskite light-emitting diodes with high radiative efficiency, reveals electronic steps that delay the radiative event.
Abstract
The kinetics of light emission in halide perovskite light-emitting diodes (LEDs) and solar cells is composed of a radiative recombination of voltage-injected carriers mediated by additional steps such as carrier trapping, redistribution of injected carriers, and photon recycling that affect the observed luminescence decays. These processes are investigated in high-performance halide perovskite LEDs, with external quantum efficiency (EQE) and luminance values higher than 20% and 80 000 Cd m−2, by measuring the frequency-resolved emitted light with respect to modulated voltage through a new methodology termed light emission voltage modulated spectroscopy (LEVS). The spectra are shown to provide detailed information on at least three different characteristic times. Essentially, new information is obtained with respect to the electrical method of impedance spectroscopy (IS), and overall, LEVS shows promise to capture internal kinetics that are difficult to be discerned by other techniques.