Introduction
Experimental section
General procedures
Device fabrication and measurement
Synthesis
Results and discussion
Synthesis
Thermal properties
Photophysical properties
Electrochemical properties
Quantum chemical calculations
Fig.6 Calculated HOMO/LUMO distributions and energy levels of the host materials. Computational Details: The geometrical and electronic properties were computed using the Gaussian 09 program package. Molecular orbitals were visualized using Gaussian view. The calculation was optimized by means of the B3LYP (Becke three parameters hybrid functional with Lee-Yang-Perdew correlation functional) [39] with the 6-31G (d) atomic basis set. Then the electronic structures were calculated at t-HCTHhyb/6–311+ + G (d, p) level [40]. Molecular orbitals were visualized using Gaussian view |
Tab.1 Physical properties of o-TPATHZ, m-TPATHZ, and p-TPATHZ |
compounds | Absa /nm | PLa /nm | Td/Tgb /°C | Egc /eV | ETd /eV | Eoxe /V | (HOMO/ LUMO)/eVe | (HOMO/ LUMO)/eVf |
---|---|---|---|---|---|---|---|---|
o-TPATHZ | 374 | 503 | 335/76 | 2.95 | 2.68 | 0.71 | –5.36/2.41 | –1.69/–4.86 |
m-TPATHZ | 376 | 512 | 365/69 | 2.93 | 2.64 | 0.75 | –5.41/–2.48 | –1.78/–4.90 |
p-TPATHZ | 370 | 490 | 402/88 | 2.97 | 2.41 | 0.71 | –5.37/–2.40 | –1.63/–4.86 |
Notes: a: Measured in CH2Cl2 at room temperature; b: Td: decomposition temperatures. Tg: glass transition temperatures; c: calculated from the onset of the absorption spectra in CH2Cl2 solution; d: measured in 2-MeTHF glass matrix at 77 K; e: estimated from the CV; f: calculated through the density function theory (DFT) |
Electroluminescence properties
Tab.2 EL data of devices A1–C1 and A2–C2 |
device | host | guest | Von /V | [hc ]a /(cd·A−1) | [hp]b /(lm·W−1) | [hEQE]c /% | roll-offd /% | CIE [x, y]e |
---|---|---|---|---|---|---|---|---|
A1 | o-TPATHZ | Ir(MDQ)2(acac) | 3.2 | 28.0 | 26.2 | 15.2/12.3/9.5 | 19.1/37.5 | (0.60, 0.40) |
B1 | m-TPATHZ | Ir(MDQ)2(acac) | 3.6 | 24.3 | 19.7 | 13.8/12.8/10.0 | 7.2/27.5 | (0.59, 0.39) |
C1 | p-TPATHZ | Ir(MDQ)2(acac) | 3.5 | 25.8 | 24.0 | 17.4/13.0/10.3 | 25.3/40.8 | (0.61, 0.38) |
A2 | o-TPATHZ | Ir(piq)3 | 3.5 | 11.1 | 10.8 | 14.4/14.2/12.8 | 1.4/11.1 | (0.68, 0.32) |
B2 | m-TPATHZ | Ir(piq)3 | 3.1 | 9.4 | 9.3 | 11.6/11.5/10.4 | 0.9/10.3 | (0.67, 0.33) |
C2 | p-TPATHZ | Ir(piq)3 | 2.9 | 13.3 | 13.6 | 16.2/16.2/15.7 | 0/3.1 | (0.68, 0.32) |
Notes: Von: turn-on voltage; a: the maximum current efficiency; b: the maximum power efficiency; c: order of the external efficiency: maximum, at 100 and 1000 cd/m2; d: the efficiency roll-off at 100 and 1000 cd/m2; e: measured at 20 mA/cm2 |
Tab.3 Compare the efficiency roll-offs with reported Ir(piq)3-based OLEDs |
device | host | guest | [hEQE ]a/% | [hEQE]b/% | roll-offc/% |
---|---|---|---|---|---|
Ref. [43] | TCPB | Ir(piq)3 | 18.6 | 10.2/7.93 | 45.2/57.4 |
Ref. [43] | TCPY | Ir(piq)3 | 18.4 | 15.5/13.8 | 15.8/25 |
Ref. [43] | TCPM | Ir(piq)3 | 18.2 | 17.8/15.4 | 2.2/15.4 |
Ref. [44] | 1d | Ir(piq)3 | 18.2 | 13.6/8.36 | 25.3/54.1 |
Ref. [44] | 2d | Ir(piq)3 | 15.8 | 12.6/9.9 | 20.3/37.3 |
Ref. [44] | 3d | Ir(piq)3 | 15.7 | 13.2/11.6 | 15.9/26.1 |
A2 | o-TPATHZ | Ir(piq)3 | 14.4 | 14.2/12.8 | 1.4/11.1 |
B2 | m-TPATHZ | Ir(piq)3 | 11.6 | 11.5/10.4 | 0.9/10.3 |
C2 | p-TPATHZ | Ir(piq)3 | 16.2 | 16.2/15.7 | 0/3.1 |
Notes: a: the maximum EQE; b: order of the external efficiency: at 100 and 1000 cd/m2; c: the efficiency roll-off at 100 and 1000 cd/m2; d: synthesized novel materials reported in Ref. [44] |