OVERSHOOT PULSES IN PEROVSKITE LIGHT EMITTING DIODES. THE ROLE OF OPERATION CONDITIONS

Hybrid perovskite light-emitting diodes (PeLEDs) are a promising new technology for the development of next-generation light sources. They are characterized by high photoluminescence (PL) and electroluminescence (EL) efficiency, which is now above 30%. In some applications, PeLEDs are expected to operate in pulsed mode. Generation of light pulses with sufficiently high intensity requires high power electrical pumping, which poses significant problems for electrical pumping and leads to deterioration of PeLED performance, its degradation or even damage. PeLEDs operating in a non-conventional regime based on the so-called overshoot effect enable generation of short, high intensity, perfectly electrically synchronizable optical pulses by using relatively low-power electrical pumping.

Here we demonstrate overshoot pulse generation by Formamidinium lead iodide (FAPI) PeLEDs and analyse their formation dependencies on temperature and time-shape of varying voltage electrical pumping pulses. The overshoot pulse intensity and shape are determined not only by the voltage and duration of pump pulses, but also on the offset voltage applied between pump pulses and negative voltage pulses applied immediately after the pump pulse termination. Intensity of overshoot pulses strongly increases at temperatures below 2̃00 K. We demonstrate that redistribution of mobile ions affecting electric field strength and its spatial distribution along the perovskite layer thickness is mainly responsible for the unusual overshoot pulse generation properties. Mathematical modelling of the electroluminescence dynamics enables to reproduce the electroluminescence dynamics and reveals two PeLED operation regimes enabling or disabling overshoot pulse generation.