Bright perovskite light-emitting diodes with improved film morphology and reduced trap density via surface passivation using quaternary ammonium salts

Abstract

Abstract Organic-inorganic hybrid perovskite light-emitting diodes (PeLEDs) have emerged as one of the promising candidates for display and illumination devices with low-cost and high color purity. However, PeLEDs exhibit bad film uniformity and high defect density, which lead to poor device performance. Herein, we introduce an additive engineering strategy employing quaternary ammonium salts, namely benzyltrimethylammonium bromide (BTABr), phenyltrimethylammonium bromide (PTABr) and benzyltrimethylammonium chloride (BTACl), in the precursor solution to prepare uniform and dense MAPbBr3 perovskite films with reduced grain sizes. These quaternary ammonium salts, which have cations containing a bulky benzyl unit, are more effective at reducing the grain sizes of MAPbBr3 perovskites. More importantly, the BTABr additive performs a dual-passivation effect to the MAPbBr3, effectively reducing the trap density within the perovskite layer as well as the proportion of non-radiative recombination of PeLEDs, and balancing the charge injection. Consequently, PeLEDs incorporating a BTABr-modified MAPbBr3 layer exhibit a reduced turn-on voltage from 4.2 to 2.6 V, and the maximum luminance and current efficiency are enhanced from 3490 Cd/m2 and 0.24 Cd/A of the reference device to 12026 Cd/m2 and 1.27 Cd/A, respectively.