2, National Cheng Kung University, Tainan, , Taiwan
The electroluminescence (EL) intensity usually is low for perovskite-based light-emitting diodes (LEDs) biased at the low current density regime and increases nonlinearly with the current density as found elsewhere in the previous studies. The traps in the active layer and the unbalanced injection of the diodes at the low current regime possibly cause the nonlinear EL intensity versus current density curve (L-I curve). In this work, by adding a small amount of additives to passivate the ionic defects of methylammonium lead bromide (CH3NH3PbBr3) polycrystalline film markedly enhances the device performance of perovskite-based LEDs. We observe the linear correlations of L-I curve for devices biased at different current regimes, which should be the feature for a decent LED. We attribute the passivation of ionic defects suppresses the trap-assisted non-radiative recombination in perovskite polycrystalline active layer and therefore elevates the output performance of devices. As characterized by SEM, XRD, and photoluminescence (PL) measurement, adding the additives reduces the averaging crystalline size, enhances PL intensity, and elongates the carrier lifetime, but did not change the basic crystal structure of CH3NH3PbBr3 perovskite. The reduced light turn-on voltage of devices also suggests the balanced injection of the carriers. Our work poses the direction for preparing the good quality of perovskite polycrystalline film for real LED applications.