Dft Based Photophysical Assessment of Novel 2-substituted-3-pyridin-2-yl-benzo-[d][1,3]-azaphosphole P-oxide for Organic Optoelectronic Applications

Phosphorus - containing heterocycles such as 1,3 - benzazaphospholes offer a tunable platform for emissive and charge - transport materials in organic electronics (OEs). Using DFT/TD - DFT at the B3LYP/6 - 31G(d,p) level, we design and evaluate nine novel donor - π - acceptor systems based on 2 - substituted - 3 - (pyridin - 2 - yl)benzo[d][1,3]azaphosphole 3 - oxide (PY-BAPO 1–9 ), with solvent (Chlorobenzene) and gas - phase analyses performed to isolate environmental effects. Targeted heteroacene Functionalization yields blue - emitting derivatives 7 – 9, which exhibit Photophysical properties ideal for blue OLEDs: tunable emission in the 440 – 510 nm (Blue/Blue-green) range, narrowed optical gaps (2.85 – 3.1 eV), high oscillator strengths ( f  ≤ 0.625) and large Stokes shifts. Their exceptionally low hole reorganization energies (λ _h  = 0.20 – 0.36 eV) additionally suggest strong potential as hole - transport materials (HTMs) for OEs. These compounds also possess good stability, reflected in global hardness values of 1.6 – 1.9 eV and low total reorganization energies (0.6 – 0.9 eV). The strong nonlinear optical response, with hyperpolarizability up to 9.25 × 10 ^− 30 esu and favorable frontier orbital alignment further underscore their multifunctional potential. This work elucidates the superior role of the pyridine terminus over phenyl in enhancing charge transfer and provides clear design guidelines for stable, efficient blue - emitting and hole - transporting phosphorus - based semiconductors for next - generation OLEDs and organic photovoltaic’s.