Issue 8, 2022

Double-type-I charge-injection heterostructure for quantum-dot light-emitting diodes


Enforcing balanced electron–hole injection into the emitter layer of quantum-dot light-emitting diodes (QLEDs) remains key to maximizing the quantum efficiency over a wide current density range. This was previously thought not possible for quantum dot (QD) emitters because of their very deep energy bands. Here, we show using Mesolight® blue-emitting CdZnSeS/ZnS QDs as a model that its valence levels are in fact considerably shallower than the corresponding band maximum of the bulk semiconductor, which makes the ideal double-type-I injection/confinement heterostructure accessible using a variety of polymer organic semiconductors as transport and injection layers. We demonstrate flat external quantum efficiency characteristics that indicate near perfect recombination within the QD layer over several decades of current density from the onset of device turn-on of about 10 μA cm−2, for both normal and inverted QLED architectures. We also demonstrate that these organic semiconductors do not chemically degrade the QDs, unlike the usual ZnMgO nanoparticles. However, these more efficient injection heterostructures expose a new vulnerability of the QDs to in device electrochemical degradation. The work here opens a clear path towards next-generation ultra-high-performance, all-solution-processed QLEDs.

Graphical abstract: Double-type-I charge-injection heterostructure for quantum-dot light-emitting diodes

Supplementary files

Article information

Article type
01 Jun 2021
18 Mar 2022
First published
26 May 2022
This article is Open Access
Creative Commons BY license

Mater. Horiz., 2022,9, 2147-2159

Double-type-I charge-injection heterostructure for quantum-dot light-emitting diodes

L. Wang, C. G. Tang, Z. Tan, H. Phua, J. Chen, W. Lei, R. Png, L. Chua and P. K. H. Ho, Mater. Horiz., 2022, 9, 2147 DOI: 10.1039/D1MH00859E

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