Synthesis and properties of push–pull porphyrins as sensitizers for NiO based dye-sensitized solar cells

Abstract

Zinc porphyrin derivatives were prepared and investigated in NiO-based p-type dye sensitized solar cells. The first series consist of trans disubstituted push–pull porphyrins containing a nitrophenyl unit as an electron withdrawing group and a benzoic acid unit as an anchoring group. An ethynyl spacer was introduced between the porphyrin meso positions and the nitrophenyl or/and the benzoic acid. In a second series a secondary electron acceptor such as benzyl-viologen or a naphthalene diimide was appended to the porphyrin. All the compounds were characterized by absorption and emission spectroscopies, theoretical calculations and by electrochemistry. The fast charge recombination certainly limits the photovoltaic performances of the first series, which remain modest (J_sc ≈ 0.5 mA cm⁻², V_oc≈ 110 mV, ff ≈ 36% and PCE ≈ 0.02%) compared to already reported highly performing sensitizers for NiO. However, promising performances (J_sc = 1.38 mA cm⁻², V_oc = 127 mV, ff = 32%, and PCE = 0.038%) were recorded for the dyad with naphthalene diimide.