1,4-Benzoxazino[2,3-b]phenoxazine and Its Sulfur Analogues: Synthesis, Properties, and Application to Organic Light-Emitting Diodes

Abstract

Several N,N‘-dialkyl or -diaryl substituted 1,4-benzoxazino[2,3-b]phenoxazines (1) and sulfur analogues 2 were prepared. They had low oxidation potentials (+0.30 − +0.41 V vs SCE for 1 and +0.39 − +0.55 V vs SCE for 2). N,N‘-Dimethyl-1,4-benzoxazinophenoxazine (1b) gave stable radical cation salts by electrochemical oxidation or a charge-transfer complex with TCNQ. The derived salts and the charge-transfer complex showed moderate conductivities in the range of 2.0 × 10-7 − 9.9 × 10-4 S cm-1. The N,N‘-diaryl deivatives had high thermal stability. Their thermal behavior was clarified by means of DSC. The applicability of these diaryl compounds as hole injection meterials (HIMs) in organic light-emitting diodes was studied by fabrication of a simple Alq-emitting device of ITO/HIM (40 nm)/NPB (10 nm)/Alq (50 nm)/LiF (0.5 nm)/Al (100 nm). The device ability was tested by measuring the luminous efficiency and the device decay time at a high current density (50 mA/cm2). The results were compared to a reference d...