Very High Efficiency Orange-Red Light-Emitting Devices with Low Roll-Off at High Luminance Based on an Ideal Host-Guest System Consisting of Two Novel Phosphorescent Iridium Complexes with Bipolar Transport

Li, Guomeng; Zhu, Dongxia; Peng, Tai; Liu, Yu; Wang, Yue; Bryce, Martin R.

Abstract

Two phosphorescent iridium complexes with bipolar transporting ability, namely FPPCA (500 nm) and BZQPG (600 nm), are synthesized and employed as an ideal host-guest system for phosphorescent organic light emitting diodes (PHOLEDs).The devices give very high-efficiency orange-red emission from BZQPG with maximum external quantum efficiency (EQE or ηext) of >27% and maximum power efficiency (PE or ηp) of >75 lm/W, and maintain high levels of 26% and 55 lm/W, 25% and 40 lm/W at high luminance of 1000 and 5000 cd m−2, respectively, within a range of 8–15 wt% of BZQPG. The realization of such high and stable EL performance results from the coexistence of two parallel paths: i) effective energy transfer from host (FPPCA) to guest (BZQPG) and ii) direct exciton formation on the BZQPG emitter, which can alternately dominate the electrophosphorescent emission. This all-phosphor doping system removes the charge-injection barrier from the charge-transport process to the emissive layer (EML) due to the inherent narrow Eg of both phosphors. Therefore, this ideal host–guest system represents a new design to produce PHOLEDs with high efficiency and low efficiency roll-off using a simple device configuration.

Citation

Li, G., Zhu, D., Peng, T., Liu, Y., Wang, Y., & Bryce, M. R. (2014). Very High Efficiency Orange-Red Light-Emitting Devices with Low Roll-Off at High Luminance Based on an Ideal Host-Guest System Consisting of Two Novel Phosphorescent Iridium Complexes with Bipolar Transport. Advanced Functional Materials, 24(47), 7420-7426. https://doi.org/10.1002/adfm.201402177

• Journal Article Type: Article
• Publication Date: Dec 17, 2014
• Deposit Date: Nov 24, 2014
• Publicly Available Date: Nov 26, 2014
• Journal: Advanced Functional Materials
• Print ISSN: 1616-301X
• Electronic ISSN: 1616-3028
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 24
• Issue: 47
• Pages: 7420-7426
• DOI: https://doi.org/10.1002/adfm.201402177
• Keywords: Electrophosphorescence, Bipolar transporting property, All-phosphor doping systems, Iridum complex, Organic LED.
• Public URL: https://durham-repository.worktribe.com/output/1417091