Benzothiadiazole derivatives functionalized with two different (hetero)aromatic donor groups: Synthesis and evaluation as TiO2 sensitizers for DSSCs

Abstract

A series of benzothiadiazole-based push-pull heterocyclic systems were synthesized and characterized in order to study the variations induced by different aromatic and heterocyclic donor groups in the optical, electronic and photovoltaic properties of DSSCs prepared with the respective cyanoacetic acid derivatives. The organic sensitizers bear a 5-hexyl-2,2'-bithienyl or N,N-diphenylanilino donor moieties conjugated with a thienyl-benzothiadiazole spacer functionalized with the electron acceptor/anchoring cyanoacetic acid group. The solar cell based on TiO2 sensitized with the novel dye bearing the 5-hexyl-2,2'-bithienyl donor, exhibited a power conversion efficiency of 0.95 % due the inefficient electron injection. Co-adsorption studies of the same dye resulted in enhanced photovoltaic conversion efficiency of 2.49 %, which represents an improvement of cell efficiency of 260 %. The sensitizer bearing the N,N-diphenylanilino donor exhibited 4.51 % power conversion efficiency, that was further enhanced by co-sensitization to 5.22 % efficiency.