The presence of two conformers of a TADF emitter has also been documented by Shi et al. in the TRZ derivative compounds TP2P-PXZ and TP5P-PXZ. Phenoxazine and a central pyridine bridge were used to promote the formation of an intramolecular hydrogen bond in TP2P-PXZ, while in the control compound TP5P-PXZ this interaction is absent. The presence of quasi-equatorial (QE) and quasi-axial (QA) conformations of TP2P-PXZ led to a self-doped system, where the QA conformer effectively acts as the host material. This led to an efficient OLED with an EQEmax of 25.4% at λEL of 548 nm while the performance of the device with TP5P-PXZ was somewhat attenuated with an EQEmax of 14.6% at a slightly red-shifted λEL of 560 nm.