Push-pull heterocyclic dyes based on pyrrole and thiophene: synthesis and evaluation of their optical, redox and photovoltaic properties

• Autor(a) principal: Fernandes, Sara Sofia Marques
• Data de Publicação: 2022
• Outros Autores: Castro, Maria Cidália Rodrigues, Ivanou, Dzmitry, Mendes, Adélio, Raposo, M. Manuela M.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: https://hdl.handle.net/1822/78288
• topic: Heterocyclic push-pull dyes; Thiophene; Pyrrole; Dye-sensitized solar cells; Auxiliary donor/acceptor heterocycles; Synthesis; auxiliary donor; acceptor heterocycles; Science & Technology

Three heterocyclic dyes were synthesized having in mind the changes in the photovoltaic, optical and redox properties by functionalization of 5-aryl-thieno[3,2-<i>b</i>]thiophene, 5-arylthiophene and <i>bis</i>-methylpyrrolylthiophene π-bridges with different donor, acceptor/anchoring groups. Knoevenagel condensation of the aldehyde precursors with 2-cyanoacetic acid was used to prepare the donor-acceptor functionalized heterocyclic molecules. These organic metal-free dyes are constituted by thieno[3,2-<i>b</i>]thiophene, arylthiophene, <i>bis</i>-methylpyrrolylthiophene, spacers and one or two cyanoacetic acid acceptor groups and different electron donor groups (alkoxyl, and pyrrole electron-rich heterocycle). The evaluation of the redox, optical and photovoltaic properties of these compounds indicate that 5-aryl-thieno[3,2-<i>b</i>]thiophene-based dye functionalized with an ethoxyl electron donor and a cyanoacetic acid electron acceptor group/anchoring moiety displays as sensitizer for DSSCs the best conversion efficiency (2.21%). It is mainly assigned to the higher molar extinction coefficient, long π-conjugation of the heterocyclic system, higher oxidation potential and strong electron donating capacity of the ethoxyl group compared to the pirrolyl moiety.