High-Efficiency Perovskite Quantum-Dot Light-Emitting Devices by Effective Washing Process and Interfacial Energy Level Alignment

Abstract

All inorganic perovskites quantum dots (PeQDs) have attracted much attention for used in thin film display applications and solid-state lighting applications, owing to their narrow band emission with high photoluminescence quantum yields (PLQYs), color tunability, and solution processability. Here, we fabricated low-driving-voltage and high-efficiency CsPbBr PeQDs light-emitting devices (PeQD-LEDs) using a PeQDs washing process with an ester solvent containing butyl acetate (AcOBu) to remove excess ligands from the PeQDs. The CsPbBr PeQDs film washed with AcOBu exhibited a PLQY of 42%, and a narrow PL emission with a full width at half-maximum of 19 nm. We also demonstrated energy level alignment of the PeQD-LED in order to achieve effective hole injection into PeQDs from the adjacent hole injection layer. The PeQD-LED with AcOBu-washed PeQDs exhibited a maximum power efficiency of 31.7 lm W and EQE of 8.73%. Control of the interfacial PeQDs through ligand removal and energy level alignment in the device structure are promising methods for obtaining high PLQYs in film state and high device efficiency.

Metal Halide Perovskites: From Crystal Formations to Light‐Emitting‐Diode Applications

“…[158] Recently, by performing both ligand exchange and purification, a high EQE of 8.73% and CE of 18.8 cd A −1 were achieved in green-emitting PeLEDs based on MHP NCs synthesized by hot injection. [48]…”

“…PeLEDs with MHP NCs that had been washed three times showed much improved EL efficiencies (EQE ≈ 6.27%, CE ≈ 13.3 cd A −1 , L ≈ 15 185 cd m −2 ) (Figure e,f) . Recently, by performing both ligand exchange and purification, a high EQE of 8.73% and CE of 18.8 cd A −1 were achieved in green‐emitting PeLEDs based on MHP NCs synthesized by hot injection …”

“…MHP NCs grown in situ are formed during film formation and do not need organic ligands; this process avoids the problems of colloidal NCs such as aggregation of NCs in high‐concentration solutions and during film formation, and impedes charge transport by insulating ligands . MHP NCs can be fabricated in situ by combining A‐site engineering methods (Section ) and NCP methods (Section ).…”

“…MHP NCs grown in situ are formed during film formation and do not need organic ligands; this process avoids the problems of colloidal NCs such as aggregation of NCs in high-concentration solutions and during film formation, [166] and impedes charge transport by insulating ligands. [48,157,158] MHP NCs can be fabricated in situ by combining A-site engineering methods (Section 2.3) and NCP methods (Section 2.3). The growth of perovskite crystals can be efficiently suppressed by dripping toluene onto spinning perovskite quasifilms Small Methods 2018, 2, 1800093 Figure 9.…”

P‐5.1: Enhanced Nickel Oxide Hole Injection Layer via the rGO Combustion Method for Perovskite QDs Light‐Emitting Diodes

“…To solve this problem, Chiba et al reported a novel washing process using an ester solvent to remove the excess ligands and achieved a EQE of 8.73% for the CsPbBr3-based LED devices. [6] Challenges remain in the form of 1) the need for further increase in the device efficiency to meet and surpass the organic LEDs (OLEDs) and inorganic quantum dot LEDs [7], and 2) the need for dramatic progress in device stability.…”