9:30 AM - 11:30 AM
[18a-PB01-1] Isomer effect on the structures and properties in nonfullerene acceptors having benzimidazole moieties
Keywords:Organic photovoltaics, Nonfullerene acceptor, Organic Semiconductor
The power conversion efficiency (PCE) of organic photovoltaic cells (OPVs) has been rapidly improved owing to the development of nonfullerene acceptors (NFAs). Recently, we reported that a new NFA [2]OBIA, in which the sulfur atom of the benzothiadiazole moiety in Y6 was replaced with the carbon atom to form the 2H-benzimidazole moiety, showed a relatively high PCEs of around 13% when blended with the benchmark polymer donor PM6. Here, we designed and synthesized [1]OBIA having the 1H-benzimidazole moiety, as a structural isomer of [2]OBIA. [1]OBIA had 0.07 eV higher HOMO and 0.04 eV higher LUMO energy levels compared to [2]OBIA, which originated in the electron-donating amine-type nitrogen. Accordingly, [1]OBIA showed red-shifted absorption spectra and hence a narrower bandgap compared to [2]OBIA. We will discuss the impact of structural isomerization in the [n]OBIAs on properties, thin film structures, and OPV performances.