Oligophenylene Tuning from Monomer to Trimer Enables Ultrafast Excited-State Dynamics and Ultrahigh Emission Cross Sections

) in the deep blue region. Computational studies attribute these properties to extended π-conjugation and high HOMO-LUMO overlap along the predominantly planar oligophenylene backbone, which enhances π-delocalization and oscillator strengths. Electroluminescent studies through fabrication of organic light-emitting diodes gave external quantum efficiencies up to 3.2%. These findings highlight the effectiveness of molecular engineering in accelerating excited-state decay while maintaining efficient light emission, establishing a promising platform for next-generation lasers, optical communications, ultrafast displays, and broadband photonic technologies.