Replacing naphthalene with anthracene π-bridge improves efficiency of D-π-A triphenylamine dyes-based dye-sensitized solar cells

Abstract

Two novel D-π-A framework type of dyes involve to a N,N-diphenylaniline (DPA) as electron donor (D) and naphthalene/anthracene π-bridge mediated between diazo (NN) functional group and carboxyl acid as an anchoring unit were designed, synthesized and utilized for dye-sensitized solar cells (DSSCs) applications. The dye, DPA-azo-N, contains a naphthalene aromatic π-bridge mediated between carboxylic acid anchor and the DPA using diazo (NN) functional group, while the dye, DPA-azo-A, uses the anthracene π-bridge. The inclusion of one more aromatic ring in the π-bridge unit of dye molecules surprisingly changed the optical and electrochemical properties of dye from DPA-azo-N to DPA-azo-A, which attributed to the fine-tune ability of this synthetic strategy for engineering the levels of energy in the dyes. The DSSCs with DPA-azo-N as a sensitizer and a I3−/I− standard electrolyte resulted 4.60% for photovoltaic conversion efficiency (η) under the air mass (AM) 1.5 G standard irradiation condition, which gained η for DSSCs those that were involved DPA-azo-A greater η (5.01%) under same irradiation conditions. For the DPA-azo-N, and DPA-azo-A sensitizers, the influence of π-bridge structure on highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels were used for obtaining the energetically well-fit condition of the I3−/I− electrolyte redox potential and TiO2 conduction bond (CB) and also efficient dye regeneration. The results inferred that synthesizing a long conjugated π-bridge unit of sensitizers can increase the η in DSSCs.