Electrochemically-stable ligands bridge the photoluminescence-electroluminescence gap of quantum dots

Abstract

Colloidal quantum dots are promising emitters for quantum-dot-based light-emitting-diodes. Though quantum dots have been synthesized with efficient, stable, and high colour-purity photoluminescence, inheriting their superior luminescent properties in light-emitting-diodes remains challenging. This is commonly attributed to unbalanced charge injection and/or interfacial exciton quenching in the devices. Here, a general but previously overlooked degradation channel in light-emitting-diodes, i.e., operando electrochemical reactions of surface ligands with injected charge carriers, is identified. We develop a strategy of applying electrochemically-inert ligands to quantum dots with excellent luminescent properties to bridge their photoluminescence-electroluminescence gap. This material-design principle is general for boosting electroluminescence efficiency and lifetime of the light-emitting-diodes, resulting in record-long operational lifetimes for both red-emitting light-emitting-diodes (T 95 > 3800 h at 1000 cd m −2) and blue-emitting light-emitting-diodes (T 50 > 10,000 h at 100 cd m −2). Our study provides a critical guideline for the quantum dots to be used in optoelectronic and electronic devices.

Quantum Dots with Highly Efficient, Stable, and Multicolor Electrochemiluminescence

“…It is interesting to observe that the inorganic–organic interface for the QDs to be applied for ECL generation needed to be different from that applied for electroluminescence in light-emitting-diodes. For the QDs in light-emitting-diodes, a recent publication 9 revealed that, for highly photoluminescent CdSe/CdS/ZnS core/shell/shell QDs, the inorganic–organic interface should not have excess zinc cations in the form of carboxylate salts. Otherwise, the light-emitting-diodes would become extremely inefficient and unstable in operation.…”

“…Different from ECL generation, the CdSe/CdS/ZnS core/shell/shell QDs have no comparative advantages over the CdSe/CdS core/shell ones on efficiency of light-emitting-diodes. 9 Furthermore, requirements of the inorganic–organic interface of the QDs for ECL and electroluminescence differ from each other drastically. Overall, these results suggest that, for a specific application—including ECL and light-emitting-diodes—of QDs, tailored design of QDs is necessary.…”

Technology progress on quantum dot light-emitting diodes for next-generation displays

“…52 The multiple QD-LED devices were interconnected by the transparent ICL. This device exhibited Pu et al 26 CdSe Electrochemically stable ligands T95@1,000 cd/m 2 > 3,800 hours for red T50@100 cd/m 2 > 10,000 hours for blue Won et al 31 InP-red HF-based surface etching for effective shell coating PLQY 98%, EQE 21.4%, T50@100 cd/m 2 > 1,000,000 hours Kim et al 32 InP 49 Typical structure Al-doped ZnO NP for ETL -Dai et al 51 Typical structure PMMA hole blocking layer EQE 20.5%, turn-on voltage 1.7 V, T50@100cd/m2 100,000 hours Sun et al 28 Inverted structure IML between ZnO/QD layers EQE 13.57% Lee et al 51 Inverted structure EDTA between ZnO/QD layers Luminance 187,186 cd/m2, EQE 5.5% Zhang et al 52 Tandem structure Stacking multiple QD-LED devices Current efficiency 41.5 cd/A, EQE 23.1% for red Current efficiency 121.5 cd/A, EQE 27.6% for green Current efficiency 17.9 cd/A, EQE 21.4% for blue Fabrication Process Coe-Sullivan et al 58 Spin-coating Phase separation during spincoating process…”

“…Pu et al reported the electrochemically stable surfacebinding ligand concept. 26 The QD layer can be degraded through an electrochemical redox reaction of the excessive carriers with the ions on the surface of the CdSe/CdS (core/shell) QD. Figure 2 (f) shows the concept of the electrochemical-inert ligand exchange.…”

Nanotreatment and Nanodiagnosis of Prostate Cancer: Recent Updates

“…QDs have ultra-high porous structure, wide surface area, lower electrochemical behavior (higher analytical signal), flexible structure, high electrical and chemical function, etc. [ 161 , 162 ]. The design of developed electrochemical biosensors can be using QDs with such special characteristics [ 163 , 164 ].…”