Impact of benzimidazole functional groups on the n-doping properties of benzimidazole derivatives

Abstract

Abstract n-Dopants play a crucial role in improving organic electronic devices through controlled doping of organic semiconductors. Benzimidazoline-based dopants have been reported as one of the best solution-processed n-type dopant precursors. In this study, two benzimidazoline-based dopants (BIBDTO and BBIBDTO) were prepared using benzo[1,2-b:4,5-b′]dithiophene as the 2-Ar unit, and their n-doping properties on the fullerene derivative PTEG-2 as the host material were carried out. For BIBDTO and BBIBDTO, respectively, the temperature at which 5% weight loss was achieved was 229 and 265°C. By comparing the ultraviolet-visible absorption spectroscopy, cyclic voltammetry, and density functional theory calculated data, it is found that BBIBDTO has a higher energy level, which is more favorable for charge transfer. Additionally, both the oxidative titration experiments and conductivity characterization of the dopants showed that BBIBDTO was more advantageous at low doping concentrations, and the BBIBDTO-doped PTEG-2 films obtained a conductivity of 0.15 S cm−1 at 10 mol% doping concentration. However, at high dopant concentrations, the dopant volume increases, potentially disrupting the microstructure. The highest conductivity of 0.29 S cm–1 was obtained at a BIBDTO doping concentration of 15 mol%. This study delves into the effect of benzimidazole functional groups on the doping performance of benzimidazoline-based dopant molecules, providing insight into designing novel efficient n-type dopant molecules and further selecting the type of dopant for various doping systems.