Novel organic dyes based on diarylmethylene-bridged triphenylamine for dye-sensitized solar cells

Abstract Three D–π–A type organic dyes, including TB-1 , TTB-1 and TTB-2 , which contained bridged triphenylamine (TPA) donor moieties, were synthesized and characterized for applications in dye-sensitized solar cells (DSSCs). Compared to TB-1 , the 5-hexyl and 3-hexyl substituted thiophene rings were introduced onto the TPA core in TTB-1 and TTB-2 . Their photophysical, electrochemical and photovoltaic properties were investigated. The reference compound L1 (the triphenylamine counterpart of TB-1 ) was also evaluated for comparison. Compared to L1 , the bridged triphenylamine based dyes studied showed enhanced performances, suggesting reasonable design of the new dyes. Meanwhile, the investigation of the three bridged TPA dyes demonstrated that by grafting 5-hexyl substituted thiophene onto the bridged TPA, TTB-1 had a significantly broader absorption spectrum in the UV–vis region, and thereby, its light harvesting ability was remarkably enhanced. Accordingly, the higher incident photon to current conversion efficiency (IPCE) of TTB-1 indicated a higher short-circuit current. In contrast, the 3-hexyl substituted thiophene in TTB-2 lead to larger steric hindrance, resulting in lower J sc value. Similar structure of TTB-1 and TTB-2 afforded almost the same V oc . Therefore, dye TTB-1 showed the best performance, exhibiting power conversion efficiency of 4.35%, with J sc of 8.61 mA cm −2 and V oc of 704 mV under simulated AM 1.5 irradiation (100 mW cm −2 ).