Large ammonium cation-induced controlled mixed-phase of CsPbBr3 perovskites for color tunable perovskite light-emitting diodes

Color tunability is a unique advantage of perovskite light-emitters for next-generation display technologies because controlled dimension and phase of metal halide perovskites can vary the optoelectronic properties of perovskite light-emitting diodes (PeLEDs). Herein, we demonstrate a color tuning of green-emitting CsPbBr3–based PeLEDs to sky-blue by employing n-butylammonium bromide (BABr). The incorporation of BABr, a large ammonium cation, in CsPbBr3 facilitates the formation of 2-dimensional (2D) perovskite structure with band-gap widening that corresponds to fluorescence peak shift from 513 to 406 nm. In addition, the incorporation of BABr is found to restrict the quick nucleation and rapid growth of CsPbBr3 crystals to allow subsequent growth of 2D structure with lower n-phases, affording a smooth and uniform film surface. As a result, the optoelectronic properties of the CsPbBr3-based PeLEDs were significantly improved by BABr with a brightness of 5260 cd m–2, peak external quantum efficiency of 6.72 % and a maximum current efficiency of 27.78 cd A–1. Moreover, the BABr addition also induced a facile color conversion from green to sky-blue, suggesting remarkable potential toward high-performance PeLEDs with tunable emission colors for next-generation display technologies.