Photo- and electro-luminescence of four cuprous complexes with sterically demanding and hole transmitting diimine ligands

Abstract

Four new cuprous complexes (1–4) containing bisphosphine and triazolylpyridine donors have been prepared in order to examine the effects of the methyl group and the carbazole appendage on photo- and electro-luminescence (PL and EL) properties. Because of their additional steric hindrance from the methyl substituent group at a 6-pyridine ring, complexes 3 and 4, compared with the methyl group free compounds 1 and 2, expectedly exhibit largely spectral blue shift and higher intensity both in PL and EL. Meanwhile, the carbazole appendage of complexes 2 and 4 does not significantly alter their PL performance in comparison with 1 and 3, respectively, but have a modest increase in their EL efficiency in multilayer organic light-emitting diodes (OLEDs). Moreover, the OLED with 4 as the light emitting material has the highest current efficiency (CE_max) of 27.2 cd A⁻¹ and the maximum external quantum efficiency (EQE_max) of 8.7%.