Doped and non-doped blue organic light-emitting diodes based on AIEgens with high exciton utilization efficiency and external quantum efficiency

Abstract

A novel molecular design strategy has been exploited for blue luminogens, NSPI-DVP and CNSPI-DVP consisting of triphenylethene (TPE) at the C5 and C10 positions of phenanthroimidazole with high-lying charge-transfer (CT) state to harvest dark triplet excitons. These materials show hybridised local and charge transfer (HLCT) states and aggregation-induced emission (AIE) properties. Non-doped OLEDs with NSPI-DVP and CNSPI-DVP show high exciton utilization efficiency (EUE) of 36.00 and 64.00%, power efficiency (PE) of 4.99 and 4.72 lm W⁻¹, external quantum efficiency (EQE) of 3.2 and 5.3% and current efficiency (CE) of 5.61 and 5.03 cd A⁻¹, respectively. The non-doped device with CNSPI-DVP shows excellent performance with negligible efficiency roll-off and high exciton utilization efficiency (EUE) than NSPI-DVP. The doped OLEDs with CBP:x wt% NSPI-DVP (EQE-7.60/8.98%) and CBP:CNSPI-DVP (EQE-8.12/9.81%) show higher efficiencies than that of non-doped devices. The improvement of C5/C10 modified phenanthrimidazole mechanofluorochromic (MFC) materials with AIE behaviour could open a new way to enhance OLEDs performances.