Sequential improvement from cosolvents ink formulation to vacuum annealing for ink-jet printed quantum-dot light-emitting diodes

Young Joon Han, Do Yeob Kim, Kunsik An, Kyung Tae Kang, Byeong Kwon Ju, Kwan Hyun Cho

Research output: Contribution to journalArticlepeer-review

Abstract

Optimization of ink-jet printing conditions of quantum-dot (QD) ink by cosolvent process and improvement of quantum-dot light-emitting diodes (QLEDs) characteristics assisted by vacuum annealing were analyzed in this research. A cosolvent process of hexane and ortho-dichlorobenzene (oDCB) was optimized at the ratio of 1:2, and ink-jetting properties were analyzed using the Ohnesorge number based on the parameters of viscosity and surface tension. However, we found that these cosolvents systems cause an increase in the boiling point and a decrease in the vapor pressure, which influence the annealing characteristics of the QD emission layer (EML). Therefore, we investigated QLEDs’ performance depending on the annealing condition for ink-jet printed QD EML prepared using cosolvents systems of hexane and oDCB. We enhanced the quality of QD EML and device performance of QLEDs by a vacuum annealing process, which was used to prevent exposure to moisture and oxygen and to promote effective evaporation of solvent in QD EML. As a result, the characteristics of QLEDs formed using ink-jet printed QD EML annealed under vacuum environment increased luminescence (L), current efficiency (CE), external quantum efficiency (EQE), and lifetime (LT50) by 30.51%, 33.7%, 21.70%, and 181.97%, respectively, compared to QLEDs annealed under air environment.

Original languageEnglish
Article number4754
Pages (from-to)1-14
Number of pages14
JournalMaterials
Volume13
Issue number21
DOIs
Publication statusPublished - 2020 Nov 1

Keywords

  • Cosolvents
  • Ink-jet printing
  • Quantum-dot (QD)
  • Quantum-dot light-emitting diodes (QLEDs)
  • Vacuum annealing

ASJC Scopus subject areas

  • Materials Science(all)

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