Department of Physics; Institute of Advanced Material
We report our effort to develop high performing all-solution-processable transparent inverted quantum-dot light-emitting diodes (QD-LEDs) by interposing an interface dipole between the ZnO electron-transporting layer (ETL) and the quantum dot light-emitting layer. It shows that the electrostatic interaction between the N+ groups in the polar conjugated polyelectrolyte molecules and the hydroxyl (OH) groups on the ZnO ETL surface creates the interface dipole. The presence of an optimal interface dipole benefits the efficient operation of QD-LEDs in two ways: (1) it effectively reduces the energy barrier at the ETL/QD emisive layer interface for efficient charge injection, and (2) it prevents the exciton quenching by suppression of ZnO surface defects. The combined effects resulted in a significant enhancement in the performance of the transparent inverted QD-LED, achieving an impressive high maximum luminance of 10011 cd/m2, which is 75% higher than that of a control device made with a pristine ZnO ETL (5721 cd/m2). QD-LEDs with an optimal interface dipole also possess a high luminous efficiency of 1.55 cd/A, which is 57% higher than that of a control QD-LED (0.99 cd/A).
Source Publication Title
Journal of Materials Chemistry C
Royal Society of Chemistry
This is the accepted manuscript version of the article. Journal of Materials Chemistry C, 2018, DOI: 10.1039/C8TC00303C. This journal is © The Royal Society of Chemistry 2018.
This work was financially supported by the Research Grants Council of Hong Kong Special Administrative Region, China, General Research Fund (GRF/12303114, 12302817), Inter-institutional Collaborative Research Scheme (RC-ICRS/15-16/04) and Shenzhen Peacock Plan (KQTD20140630110339343).
Link to Publisher's Edition
Journal of Materials Chemistry C, 2018, DOI: 10.1039/C8TC00303C.