Theoretical study on electronic and optoelectronic properties of some C^N^N- and C^C^C-chelated iridium(III) complexes for OLEDs.

The electronic and optoelectronic properties of 8 C^N^N- and C^C^C-chelated Ir(III) complexes were investigated using density functional theory at the Becke-style 3-parameter Lee-Yang-Par and triple zeta plus polarization level. Based on reorganization energy calculations, complex 7 was identified as a promising ambipolar material, while complexes 1 and 2 had efficient hole transport properties. Complex 8 had low ionization potential and is therefore a strong candidate for hole transport applications. Complex 4 had high electron affinity and therefore has potential as an effective electron acceptor material. Photophysical analysis showed that all complexes had phosphorescent properties, with complexes 5 and 6 showing particularly small singlet-triplet energy gaps, making them ideal for high-performance phosphorescent organic light-emitting diodes (PhOLEDs). The intersystem crossing and reverse intersystem crossing rates indicated that these complexes are more likely to have phosphorescence rather than thermally activated delayed fluorescence. These findings provide valuable insights for the design of efficient OLED materials.