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

RSC Advances Pub Date: 2019-01-23 DOI: 10.1039/C8RA09486A

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 (Tg), 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, ηex: 4.90%, ηc: 6.0 cd A?1, and ηp: 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, ηex: 4.70%, ηc: 5.7 cd A?1, and ηp: 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, ηex of 19.3%, ηc of 27.9 cd A?1 and ηp 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, ηex of 19.9%, ηc of 26.0 cd A?1 and ηp of 27.0 lm W?1 with CIE coordinates of (0.64, 0.37).

Graphical abstract: Efficient full-colour organic light-emitting diodes based on donor–acceptor electroluminescent materials with a reduced singlet–triplet splitting energy gap
Recommended Literature