Carrier transport mechanisms of phosphorescent organic light-emitting devices fabricated utilizing a N,N'-dicarbazolyl-3,5-benzene: 1,3,5-tri(phenyl-2-benzimidazole)-benzene mixed host emitting layer

Dong Chul Choo; Hyun Sung Bang; Tae Whan Kim; Ji Hyun Seo; Young Kwan Kim

doi:10.1166/jnn.2012.4587

Carrier transport mechanisms of phosphorescent organic light-emitting devices fabricated utilizing a N,N'-dicarbazolyl-3,5-benzene: 1,3,5-tri(phenyl-2-benzimidazole)-benzene mixed host emitting layer

J Nanosci Nanotechnol. 2012 Feb;12(2):1649-53. doi: 10.1166/jnn.2012.4587.

Authors

Dong Chul Choo¹, Hyun Sung Bang, Tae Whan Kim, Ji Hyun Seo, Young Kwan Kim

Affiliation

¹ Department of Electronics and Computer Engineering, Hanyang University, Seoul 133-791, Korea.

PMID: 22630021
DOI: 10.1166/jnn.2012.4587

Abstract

The electrical and the optical properties of phosphorescent organic light-emitting devices (PHOLEDs) fabricated utilizing a mixed host emitting layer (EML) consisting of N,N'-dicarbazolyl-3,5-benzene (mCP) and 1,3,5-tri(phenyl-2-benzimidazole)-benzene (TPBi) were investigated to clarify the carrier transport mechanisms of PHOLEDs. While the operating voltage of the PHOLEDs with a mixed host EML significantly decreased due to the insertion of TPBi with a high electron mobility, the quantum efficiency of the PHOLEDs decreased due to the hindrance of the exciton energy transfer by TPBi molecules. The electroluminescence spectra for the PHOLEDs with an tris(2-phenylpyridine)iridium-doped mixed host EML showed that the TPBi molecules in the mixed host EML increased the electron injection into the mixed host EML, resulting in a decrease of the shift length of the recombination zone in comparison with a single host EML.