Perovskite Quantum Dots with Ultralow Trap Density by Acid Etching‐Driven Ligand Exchange for High Luminance and Stable Pure‐Blue Light‐Emitting Diodes

Abstract

The research on metal halide perovskite light‐emitting diodes (PeLEDs) with green and infrared emission has demonstrated significant progress in achieving higher functional performance. However, the realization of stable pure‐blue (≈470 nm wavelength) PeLEDs with increased brightness and efficiency still constitutes a considerable challenge. Here, a novel acid etching‐driven ligand exchange strategy is devised for achieving pure‐blue emitting small‐sized (≈4 nm) CsPbBr3 perovskite quantum dots (QDs) with ultralow trap density and excellent stability. The acid, hydrogen bromide (HBr), is employed to etch imperfect [PbBr6]4− octahedrons, thereby removing surface defects and excessive carboxylate ligands. Subsequently, didodecylamine and phenethylamine are successively introduced to bond the residual uncoordinated sites of the QDs and attain in situ exchange with the original long‐chain organic ligands, resulting in near‐unity quantum yield (97%) and remarkable stability. The QD‐based PeLEDs exhibit pure‐blue electroluminescence at 470 nm (corresponding to the Commission Internationale del'Eclairage (CIE) (0.13, 0.11) coordinates), an external quantum efficiency of 4.7%, and a remarkable luminance of 3850 cd m−2, which is the highest brightness reported so far for pure‐blue PeLEDs. Furthermore, the PeLEDs exhibit robust durability, with a half‐lifetime exceeding 12 h under continuous operation, representing a record performance value for blue PeLEDs.

Interfacial “Anchoring Effect” Enables Efficient Large‐Area Sky‐Blue Perovskite Light‐Emitting Diodes

“…It is well known that the improvement of transient PL lifetimes is ascribed to the reduction of trap‐mediated nonradiative recombinations. [ 18 , 24 ] In addition, the photoluminescence quantum efficiencies (PLQYs) of perovskite films with various APDO‐doping concentrations are collected in Figure S6 (Supporting Information) for comparison. The PLQYs of APDO‐modified samples show much higher values than that of the control one, providing a direct evidence for the passivation effect of the interface engineering.…”

“…The high stability of EL spectra in APDO‐modified device can be attributed to the reduced defects in perovskite films, which can behave as the main channel for halide ion migration and phase segregation, along with facilitating device degradation under external stimulations. [ 18 ]…”

“…[15][16][17] Furthermore, the degradation of blue PeLEDs will be accelerated because the defects can act as the hoping sites for ion migration under external bias. [18] To produce uniform perovskite films with suppressed trap-states, various strategies have been proposed, including stoichiometric-composition engineering, dimensional manipulation, A-site cation doping, Lewis-base passivation and so on. [11][12][13][19][20][21] Besides, the interface between perovskite films and the underlying hole-transport layer (HTL) has a strong influence on the perovskite crystallization behaviors and electrical properties.…”

“…[ 15 , 16 , 17 ] Furthermore, the degradation of blue PeLEDs will be accelerated because the defects can act as the hoping sites for ion migration under external bias. [ 18 ]…”

Highly stable and bright blue light-emitting diodes based on carbon dots with a chemically inert surface

“…Low quantum efficiency, inferior saturated color purity and poor stability become bottlenecks of the development of blue LEDs which still hardly break out nowadays. [2,[4][5][6][7][8][9][10][11] Carbon dots (CDs) are one type of brand-new zero dimensional materials based on carbon nanomaterials, which have large amounts of applications in biological imaging, optoelectronics, biosensors, photoelectrocatalysis, medical treatments and LEDs. [12][13][14][15] Due to nontoxicity, environmental protection, good biocompatibility and simple synthesis methods, CDs have tremendous advantages in optical materials field.…”