Intramolecular hydrogen bonds assist in controlling the quantum well distribution in quasi-2D perovskites for efficient pure-blue perovskite light-emitting diodes

Abstract

Quantum well distribution in quasi-2D perovskites plays a vital role in the device performance of blue perovskite light-emitting diodes (PeLEDs). Here, an organic ligand of 2-fluorophenylethylammonium bromide (o-F-PEABr) containing a potential intramolecular hydrogen bond is used to mediate the organic ligand anchoring with quasi-2D perovskites for developing efficient blue PeLEDs. With regard to the commonly used organic ligand phenethylammonium bromide (PEABr), the ortho-position fluorine atom in o-F-PEABr can form intramolecular hydrogen bonds with the adjacent ammonium group. It is found that the o-F-PEABr ligand effectively mediates the quantum well distribution in blue quasi-2D perovskites with fewer low n-value phases and more high n-value phases (n ≥ 4) than the control quasi-2D perovskites prepared with the PEABr ligand. The blue quasi-2D perovskites prepared with o-F-PEABr exhibit more efficient energy transfer among different quantum wells and enhanced photoluminescence quantum yield, which not only lowers the turn-on voltage but also effectively improves the light-emitting efficiency of the resultant blue PeLEDs. The PeLEDs based on the quasi-2D perovskites prepared with o-F-PEABr achieve a maximum external quantum efficiency of 7.55% and a pure-blue emission at 475 nm with CIE coordinates of (0.111, 0.113).