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

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).


SI-I: Charge-Transfer intexes
The hole-particle pair interactions have been related to the distance covered during the excitations one possible descriptor Δr intex could be used to calculate the average distance which is weighted in function of the excitation coefficients.

Table S1 :
Photophysical properties of Cz-DEPVI in different solvents.

Table S3 .
Percentage transition of LE and CT of Cz-DEPVI and TPA-DEPVI

Table S7 :
Computed RMSD of electron and hole, H index and t index for ten singlet states (S 1 -S 10 ) of Cz-DEPVI

Table S8 :
Computed RMSD of electron and hole, H index and t index for first ten singlet states (S 1 -S 10 ) of TPA-DEPVI

Table S9 :
Computed hole and electron overlap (S), distance between centroids of hole and electron (D, Å) and dipole moment (µ) for ten S 1 -S 10 states of Cz-

Table S10 :
Computed hole and electron overlap (S), distance between centroids of hole and electron (D, Å) and dipole moment (µ) for ten S 1 -S 10 states of TPA-DEPVI