Unraveling the photophysical properties of 4CzIPN doped in different hosts: a theoretical study

The development of both thermally activated delayed fluorescence (TADF) emitters and host materials plays a crucial role in achieving high quantum efficiency in organic light-emitting diode (OLED) devices. While numerous host materials have been designed and used for TADF emitters, the structure-property relationship of hosts and their influence on the luminescence properties of TADF emitters remain relatively unexplored. In this work, the structure-property relationship of 13 host materials and their influence on the luminescence properties of the classical TADF molecule 4CzIPN are investigated. Based on molecular dynamics (MD) simulations, the doped host-guest systems at different time snapshots are selected for computational and statistical averaging analyses. Our results reveal that mCP, a commonly used host, weakens Dexter energy transfer (DET), suppresses structural variation, and facilitates high color purity in the emission of 4CzIPN. In contrast, CBP can enhance the oscillator strength and spin-orbit coupling (SOC) of 4CzIPN in the doped film. Host material mCP-OMe, which shares structural similarities with mCP, combines the advantages of both mCP and CBP. 4CzIPN in mCP-OMe:4CzIPN films exhibits reduced non-radiative loss, higher oscillator strength, and enhanced up-conversion. The results obtained through cluster analysis of the simulated structures agree well with the statistical average results. This study provides a theoretical foundation for selecting and designing more efficient host materials for 4CzIPN.