Abstract
Quantum-confined CsPbBr3 nanoplatelets (NPLs) are extremely promising for use in low-cost blue light-emitting diodes, but their tendency to coalesce in both solution and film form, particularly under operating device conditions with injected charge-carriers, is hindering their adoption. We show that employing a short hexyl-phosphonate ligand (C6H15O3P) in a heat-up colloidal approach for pure, blue-emitting quantum-confined CsPbBr3 NPLs significantly suppresses these coalescence phenomena compared to particles capped with the typical oleyammonium ligands. The phosphonate-passivated NPL thin films exhibit photoluminescence quantum yields of ∼40% at 450 nm with exceptional ambient and thermal stability. The color purity is preserved even under continuous photoexcitation of carriers equivalent to LED current densities of ∼3.5 A/cm2. 13C, 133Cs, and 31P solid-state MAS NMR reveal the presence of phosphonate on the surface. Density functional theory calculations suggest that the enhanced stability is due to the stronger binding affinity of the phosphonate ligand compared to the ammonium ligand.
Highlights
Story of the Invention of Efficient InGaN Blue-Light-Emitting Diodes (Nobel Lecture)
We found that the photoluminescence quantum yield (PLQY) shows an increase from 25% when HPA/Pb = 0 (OLANPLs) to ∼40% when HPA/Pb = 1.5 for CsPbBr3 NPL thin films, indicating that radiative recombination pathways are more effectively out-competing nonradiative pathways in the HPA-NPLs
It is widely accepted that the detachment of ligands causes CsPbBr3 NPLs to coalesce, leading to a loss of quantum confinement.[14,15]
Summary
Story of the Invention of Efficient InGaN Blue-Light-Emitting Diodes (Nobel Lecture).
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