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

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 (CEmax) of 27.2 cd A(-1) and the maximum external quantum efficiency (EQE(max)) of 8.7%.