Triphenylsilyl-promoted amorphization and its induced enhanced emission in ultraviolet-emissive terphenyls

Abstract

The advancement of organic light-emitting diodes technology has increased the demand for luminescent materials with high solid-state luminescence efficiency and stable amorphous properties, particularly for ultraviolet (UV)-emitting materials, where doping strategies are ineffective. This study focuses on improving the amorphous stability of UV-emissive 2′,5′-dioxy-p-terphenyls by incorporating triorganosilyl groups at the 3 and 3′′-positions, enhancing their glass transition temperature and preventing crystallization. Density functional theory calculations confirm that silyl group incorporation has minimal impact on the electronic structure, maintaining UV emission. The silicon-decorated terphenyls that are readily synthezied exhibit higher thermal stability and improved amorphous properties compared to their parent counterparts. Differential scanning calorimetry analysis reveals that terphenyls modified with triphenylsilyl groups show the highest glass transition temperature and amorphous stability. Photophysical analysis demonstrates that these materials exhibit amorphization-induced enhanced emission, a rare phenomenon where fluorescence efficiency in the amorphous state is higher than that in the crystalline state. These findings highlight the effectiveness of silicon-based molecular modifications in stabilizing amorphous nature of UV-emitting materials. The approach preserves the UV-emissive properties of the parent chromophores while improving their thermal and morphological stability and luminescence efficiency in the amorphous state.