An efficient solution-processable non-doped hybridized local and charge-transfer (HLCT) emitter for a simplified organic light-emitting diode

Abstract

Here, a new solution-processable hybridized local and charge-transfer (HLCT) fluorescent molecule, CPBzFC, is designed and synthesized as an efficient emitter for low-cost and simple-structured electroluminescent devices. CPBzFC contains 7-(4-(carbazol-N-yl)phenyl)benzothiadiazole as an HLCT fragment directly linked to a hole-transporting and highly soluble 7-(3,6-di-tert-butylcarbazol-N-yl)-9,9′-bis(8-(3,6-di-tert-butylcarbazol-N-yl)octyl)fluorene part. The photophysical results and theoretical calculations unveil an HLCT excited-state character with a strong yellowish-green fluorescence emission (a solid-state photoluminescence quantum yield of 82%), decent hole-transporting mobility, good film morphology, and thermal and electrochemical stabilities. CPBzFC is successfully utilized as a solution-processed non-doped emitter in simple structured OLEDs. This device achieves excellent electroluminescence (EL) performance with an ultra-high brightness of 30 800 cd m⁻², a maximum external quantum efficiency (EQE_max)of 6.74%, a maximum current efficiency (CE_max) of 14.38 cd A⁻¹, and a high exciton utilization efficiency (EUE) of 41%.