New hole injection layer (HIL) materials for organic light-emitting diodes (OLEDs) based on phenothiazine and phenoxazine were synthesized, and the electro-optical properties of the synthesized materials were examined by UV-vis and PL spectra, and by CV. 1-PNA-BPBPOX showed glass transition temperatures of 161 degree, which was higher than that (110 degree) of 2-TNATA, a commercial HIL material. The HOMO levels of the synthesized materials were 4.9-4.8 eV, indicating a good match between the HOMO of indium tin oxide (ITO) (4.8 eV) and the HOMO of NPB (5.4 eV), a common hole transfer layer (HTL) material. The synthesized materials were used as the HIL in OLED devices, yielding power efficiencies of 2.8 lm/W (1-PNABPBPOX) and 2.1 lm/W (2-TNATA). These results indicate that 1-PNABPBPOX yields a higher power efficiency, by a factor of 33%, than the 2-TNATA commercial HIL material. Also, 1-PNA-BPBPOX exhibited a longer device lifetime than 2-TNATA.