Abstract
The industrialization of quantum dot light-emitting diodes (QLEDs) requires the use of less hazardous cadmium-free quantum dots, among which ZnSe-based blue and InP-based green and red quantum dots have received considerable attention. In comparison, the development of InP-based green QLEDs is lagging behind. Here, we prepare green InP/ZnSe/ZnS quantum dots with a diameter of 8.6 nm. We then modify the InP quantum dot emitting layer by passivation with various alkyl diamines and zinc halides, which decreases electron mobility and enhances hole transport. This, together with optimizing the electron transport layer, leads to green 545 nm InP QLEDs with a maximum quantum efficiency (EQE) of 16.3% and a current efficiency 57.5 cd/A. EQE approaches the theoretical limit of InP quantum dots, with an emission quantum yield of 86%.
Highlights
The industrialization of quantum dot light-emitting diodes (QLEDs) requires the use of less hazardous cadmium-free quantum dots, among which zinc selenide (ZnSe)-based blue and indium phosphide (InP)-based green and red quantum dots have received considerable attention
QLEDs incorporating a number of other quantum dots (QDs), such as InP, ZnSe, CuInS2, and lead halide perovskites, etc., have been widely studied[12,13,14,15,16,17], among which indium phosphide (InP)-based and zinc selenide (ZnSe)-based QDs are considered as promising benign alternatives, which are capable of covering nearly the full range of natural colors[3,18,19,20,21,22,23,24]
The asprepared green InP/ZnSe/ZnS core/shell/shell QDs containing oleic acid ligands were measured to have an average diameter of ~8.6 ± 1.2 nm
Summary
The industrialization of quantum dot light-emitting diodes (QLEDs) requires the use of less hazardous cadmium-free quantum dots, among which ZnSe-based blue and InP-based green and red quantum dots have received considerable attention. To circumvent the obstacle of electron/hole mismatch in green InP QLEDs, considerable efforts have been made to improve the energy-level alignment between the highest occupied molecular orbital (HOMO) of HTL and valence band of the InP QDs by tailoring the shell structure of QDs7,36. These methods are, nontrivial, which must undergo modification by the synthesis of QDs multilayer structure. The above modification, in theory, depends on the properties of the as-prepared InP QDs in terms of core/shell structure, original ligand passivation and importantly the emission quantum yield The latter should be sufficiently high for the QLEDs performance, which is commonly inferior for InP QDs (cf CdSe QDs). Detail of results and discussion is elaborated
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