From Donor–Donor Exciplex-Forming Interfaces to Detection of an Explosive Compound with Phenylethenyl Derivatives Redefining OLED Efficiency and Extremely High Sensitivity to Picric Acid

High Resolution Image Download MS PowerPoint Slide In this study, three derivatives of phenylethenyl-substituted phenoxazine and phenothiazine are synthesized via Buchwald-Hartwig cross-coupling, targeting multifunctionality as exciplex-forming materials and efficient cyan emitters for organic light-emitting diodes (OLEDs) and sensitive dectectors of picric acid. Advanced density functional theory (DFT) calculations at the mPW1PW91/6–31G(d,p) level unveil the intricate electronic architectures of these compounds, emphasizing their spatial molecular orbitals and the charge-transfer dynamics governing excited-state properties. Reorganization energy calculations indicate superior hole mobility, particularly for derivatives with tetraphenylethenyl groups. Photophysical investigations reveal aggregation-induced emission enhancement (AIEE) in water-THF mixtures, with cyan fluorescence intensifying at high water fractions ( f w % = 99) due to the formation of emissive aggregates. Photoluminescence quantum yields (PLQYs) are significantly higher of solid films (13.5–53%) compared to those of dilute toluene solutions (3–26%). This observation is attributed to enhanced intermolecular interactions and aggregate formation. The emissive aggregates of the compounds exhibit extremely high sensitivity to electron-deficient picric acid via noncovalent interactions with Stern–Volmer constants up to 2.96 × 10 4 M –1 . This is attributed to their strong donor–acceptor charge-transfer mechanisms. OLEDs employing these materials as emitters display bluish-cyan electroluminescence (λ max ≈500 nm), with brightness surpassing 1000 cd/m 2 and external quantum efficiencies (EQEs) ranging from 2.5 to 6%. The relatively high EQEs are explained by triplet harvesting from interface donor–donor exciplexes.