Effect of bulky side groups on photophysical properties and electroluminescent performance of oligo(styryl)benzenes
Fernando de Lera-Garrido, Rocío Domínguez, M. Paz Fernández‐Liencres, Cristina Martín, Juan Tolosa, Eva M. García‐Frutos, Josefina Perles, Johan Hofkens, Joaquín C. Garcı́a-Martı́nez, Andrés Garzón‐Ruiz, Amparo Navarro
Abstract
The rational design of electroluminescent compounds has been recognized as a promising strategy to maximize the efficiency of electronic devices. In this work, we analyze the impact of the substitution of n-alkyl and n-alkoxy side chains by bulkier side groups (tert-butyl and tert-butoxy) on the photophysics of the two model fluorophores 1,3,5-tris(styryl)benzene and 1,2,4,5-tetra(styryl)benzene. We found that the bulky side groups have a significant contribution to the vibrational normal modes associated with the non-radiative deactivation. The aggregation-induced enhanced emission phenomenon observed in some cases was attributed to the blocking of the trans→cis photoisomerization and the restriction of intramolecular vibrations. In the solid state, the bulky side groups have demonstrated to play a determining role in the supramolecular structure and photophysical properties, particularly in the case of the tetra(styryl)benzenes. In light-emitting devices, we found that the incorporation of the bulky side groups in oligo(styryl)benzenes could reduce the electromer formation and improve the device performance. The tetra(styryl)benzenes, and particularly the tert-butyl derivative, showed better device performance, with lower turn-on voltage, higher current density and electroluminescent intensity.