Design strategy and molecular level understanding: hole transport materials with suitable transition dipole orientation for OLEDs†

The development of hole transport materials with desirable properties is important for the fabrication of efficient organic light-emitting diodes (OLEDs). The present work demonstrates an approach for developing a library of phenothiazine-based hole transport materials (HTMs) for OLED application with considerably good triplet energy (theoretical). Furthermore, the single-crystal structure analysis at the molecular level for some of the developed molecules reveals the possibility of poor electronic communications between the corresponding units. Theoretical studies on transition dipole orientation revealed that all the present phenothiazine-based molecules have appreciable transition dipole orientation. Hence, the objective of the current work has been to assess the impact of chemical structures on certain features of a group of phenothiazine-based functional molecular HTMs with donor–acceptor characteristics. Finally, the hole-only devices (HODs) were fabricated with the synthesized materials as HTMs, and these showed an enhancement in current density with the increase in operating voltage from ∼2–8 V. All these theoretical and experimental outcomes suggested that the present set of molecules could be used as possible efficient HTMs for OLED applications.