Effect of triplet energy and transporting property of electron transporting material on iridium complex yellow phosphorescent organic light-emitting devices

Wen Wen; Junsheng Yu; Sujie Chen; Chunhua Huang; Yadong Jiang

doi:10.1117/12.866332

22 October 2010 Effect of triplet energy and transporting property of electron transporting material on iridium complex yellow phosphorescent organic light-emitting devices

Wen Wen, Junsheng Yu, Sujie Chen, Chunhua Huang, Yadong Jiang

Author Affiliations +

Proceedings Volume 7658, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optoelectronic Materials and Devices for Detector, Imager, Display, and Energy Conversion Technology; 76580G (2010) https://doi.org/10.1117/12.866332
Event: 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies, 2010, Dalian, China

Abstract

Balanced charge carrier and appropriate exciton confinement are considered as the key factors for the realization of highly efficient and stable organic light-emitting devices (OLEDs). An effective way to reach a loss free hole-electron recombination and exciton leakage is to use suitable electron transporting layers (ETLs). To investigate the influence of triplet energy and electron transporting properties of ETLs on the performance of iridium complex yellow phosphorescent OLEDs, we fabricated three devices based on bis[2-(4-tert-butylphenyl)benzothiazolato-N,C2']iridium (acetylacetonate) [(t-bt)2Ir(acac)] doped 4,4'-bis(carbazol-9-yl) biphenyl (CBP) host by using 2,9-dimethyl-4,7-diphenyl- 1,10-phenanthroline (BCP), 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi), and 4,7-diphyenyl-1,10- phenanthroline (BPhen) as ETLs, respectively. It was found that there was no apparent correlation between the device efficiency and the triplet energy of ETLs. Instead, device efficiency was determined by the electron mobility of ETLs only. With an optimized device using BPhen as ETL, a power efficiency of 23.1 lm/W and a current efficiency of 28.0 cd/A at 0.08 mA/cm² were achieved, which was much higher than that of the control devices (7.5 lm/W for BCP-device and 8.5 lm/W for TPBi-device). The improved efficiency was attributed to that BPhen had the highest electron mobility and provided better charge balance in the hole-dominant devices. Moreover, the EL spectra of three devices showed no obvious difference with a light emission from iridium complex peaked at 562 nm and a shoulder peak at 600 nm. This indicated that no matter BCP, TPBi or BPhen acted as ETLs, the (t-bt)₂Ir(acac) triplet exciton can be confined within the emissive layer effectively.

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Wen Wen, Junsheng Yu, Sujie Chen, Chunhua Huang, and Yadong Jiang "Effect of triplet energy and transporting property of electron transporting material on iridium complex yellow phosphorescent organic light-emitting devices", Proc. SPIE 7658, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optoelectronic Materials and Devices for Detector, Imager, Display, and Energy Conversion Technology, 76580G (22 October 2010); https://doi.org/10.1117/12.866332

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KEYWORDS

Electron transport

Excitons

Iridium

Energy efficiency

Organic light emitting diodes

Electroluminescence

Optoelectronic devices

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