in toluene) and similar FPL (65.8%; in 2 wt% mCBP) to those of its analogue PXZ-TRZ (545 nm in toluene, FPL 65.7%; 6 wt% in CBP) while the ΔEST (0.07 eV) of PTZ-TRZ is the largest amongst the three compounds: DMAC-TRZ, PXZ-TRZ and PTZ-TRZ. The relatively similar electron-donating strength of the PXZ and PTZ groups in PXZ-TRZ and PTZ-TRZ translates to similar emission spectra and FPL. The device containing PTZ-TRZ exhibited an EQEmax of 10.8%, which is also of similar performance to that of PTZ-TRZ-based OLED although the two reports used different hosts within the emissive layer. The EL spectrum shows two emission bands, one high-energy band at around 393 nm and a stronger broad band at 532 nm, resulting from the simultaneous emission from the two conformers.