Controlling Horizontal Dipole Orientation and Emission Spectrum of Ir Complexes by Chemical Design of Ancillary Ligands for Efficient Deep-Blue Organic Light-Emitting Diodes

Hyun Shin; Yeon Hee Ha; Hyun-Gu Kim; Ran Kim; Soon-Ki Kwon; Yun-Hi Kim; Jang-Joo Kim

doi:10.1002/adma.201808102

Controlling Horizontal Dipole Orientation and Emission Spectrum of Ir Complexes by Chemical Design of Ancillary Ligands for Efficient Deep-Blue Organic Light-Emitting Diodes

Adv Mater. 2019 May;31(21):e1808102. doi: 10.1002/adma.201808102. Epub 2019 Apr 10.

Authors

Hyun Shin¹, Yeon Hee Ha², Hyun-Gu Kim¹, Ran Kim², Soon-Ki Kwon³, Yun-Hi Kim², Jang-Joo Kim^{1

4}

Affiliations

¹ Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, South Korea.
² Department of Chemistry and RIGET, Gyeongsang National University, Jinju, 52828, South Korea.
³ Department of Materials Engineering and Convergence Technology and ERI, Gyeongsang National University, Jinju, 52828, South Korea.
⁴ Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul, 08826, South Korea.

PMID: 30972824
DOI: 10.1002/adma.201808102

Abstract

Deep-blue emitting Iridium (Ir) complexes with horizontally oriented emitting dipoles are newly designed and synthesized through engineering of the ancillary ligand, where 2',6'-difluoro-4-(trimethylsilyl)-2,3'-bipyridine (dfpysipy) is used as the main ligand. Introduction of a trimethylsilyl group at the pyridine and a nitrogen at the difluoropyrido group increases the bandgap of the emitter, resulting in deep-blue emission. Addition of a methyl group (mpic) to a picolinate (pic) ancillary ligand or replacement of an acetate structure of pic with a perfluoromethyl-triazole structure (fptz) increases the horizontal component of the emitting dipoles in sequence of mpic (86%) > fptz (77%) > pic (74%). The organic light-emitting diode (OLED) using the Ir complex with the mpic ancillary ligand shows the highest external quantum efficiency (31.9%) among the reported blue OLEDs with a y-coordinate value lower than 0.2 in the 1931 Commission Internationale de L'Eclairage (CIE) chromaticity diagram.

Keywords: ancillary ligands; chemical design; deep-blue iridium complexes; horizontally oriented emitting dipoles; organic light-emitting dipoles.

Abstract

Grants and funding