Efficient full-colour organic light-emitting diodes based on donor-acceptor electroluminescent materials with a reduced singlet-triplet splitting energy gap

Jayaraman Jayabharathi; Ramaiyan Ramya; Venugopal Thanikachalam; Palanivel Jeeva; Elayaperumal Sarojpurani

doi:10.1039/c8ra09486a

Efficient full-colour organic light-emitting diodes based on donor-acceptor electroluminescent materials with a reduced singlet-triplet splitting energy gap

RSC Adv. 2019 Jan 23;9(6):2948-2966. doi: 10.1039/c8ra09486a. eCollection 2019 Jan 22.

Authors

Jayaraman Jayabharathi¹, Ramaiyan Ramya¹, Venugopal Thanikachalam¹, Palanivel Jeeva¹, Elayaperumal Sarojpurani^{1

2}

Affiliations

¹ Department of Chemistry, Annamalai University Annamalai Nagar Tamilnadu 608 002 India.
² Sri Manakula Vinayagar Engineering College India.

Abstract

A series of efficient blue-emitting materials, namely, Cz-DPVI, Cz-DMPVI, Cz-DEPVI and TPA-DEPVI, possessing a donor-acceptor architecture with dual carrier transport properties and small singlet-triplet splitting is reported. These compounds exhibit excellent thermal properties with a very high glass-transition temperature (T _g), and thus, a stable uniform thin film was formed during device fabrication. Among the weak donor compounds, specifically, Cz-DPVI, Cz-DMPVI and Cz-DEPVI, the Cz-DEPVI-based device showed the maximum efficiencies (L: 13 955 cd m^-2, η _ex: 4.90%, η _c: 6.0 cd A^-1, and η _p: 5.4 lm W^-1) with CIE coordinates of (0.15, 0.06) at 2.8 V. The electroluminescent efficiencies of Cz-DEPVI were higher than that of the strong donor TPA-DEPVI-based device (L: 13 856 cd m^-2, η _ex: 4.70%, η _c: 5.7 cd A^-1, and η _p: 5.2 lm W^-1). Furthermore, these blue emissive materials were used as hosts to construct efficient green and red phosphorescent OLEDs. The green device based on Cz-DEPVI:Ir(ppy)₃ exhibited the maximum L of 8891 cd m^-2, η _ex of 19.3%, η _c of 27.9 cd A^-1 and η _p of 33.4 lm W^-1 with CIE coordinates of (0.31, 0.60) and the red device based on Cz-DEPVI:Ir(MQ)₂(acac) exhibited the maximum L of 40 565 cd m^-2, η _ex of 19.9%, η _c of 26.0 cd A^-1 and η _p of 27.0 lm W^-1 with CIE coordinates of (0.64, 0.37).