Dynamic Response of Alternating-Current-Driven Light-Emitting Diodes Based on Hybrid Halide Perovskites

In this work, we report the dynamic response of alternating-current-driven light-emitting diodes based on a range of hybrid halide perovskites. Electroluminescence (EL), which appears only in the positive section of a dc voltage, arises in both cycles under a sinusoidal ac voltage. Appearance of EL emission in negative cycles of the ac voltage is explained in terms of available residual charges injected in the previous positive cycle of the sinusoidal voltage; the relative intensity of EL emission in the negative cycle can be correlated to the ambipolarity of charge carriers in the ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}{\mathrm{Pb}\mathrm{Br}}_{x}{\mathrm{I}}_{3\text{\ensuremath{-}}x}$ series. At low frequencies of the ac voltage, the dynamic response of EL emission in any cycle is in phase with the applied ac voltage; interestingly, the EL emission starts to lag the sinusoidal voltage at higher frequencies. The phase lag also has a correlation to the ambipolarity of the active perovskite material. Finally, the frequency dependence of EL emission under an ac voltage provides the limiting frequency of device operation (\ensuremath{-}3 dB frequency) and thereby the effective carrier mobility in the active heterostructure.