n-Type pyromellitic diimide-benzodithiophene-containing conjugated polymers for all-polymer solar cells with high open-circuit voltage

•New n-Type conjugated polymers based on pyromellitic diimide units are synthesized.•Electrochemical results illustrate that both polymers have LUMO levels at −3.5 to −3.6 eV.•All-polymer solar cells based on the prepared polymers are fabricated.•The PSC based on the blend of P3HT and P2 shows a high Voc of 0.96 V.

n-Type conjugated polymers were synthesized by using pyromellitic diimide monomers with two different alkyl side chain substitutions as electron-accepting units and benzodithiophene as electron-donating unit via Stille coupling reaction. The obtained polymers were characterized by UV–vis spectroscopy and cyclic voltammetry. The results illustrate that the substituted alkyl side chains 2-ethylhexyl and 2-octyldodecyl have negligible effect on the optical properties of the resulting polymers. The LUMO levels of the polymers located at −3.5 to −3.6 eV. All-polymer bulk heterojunction solar cell with “P3HT” as p-type polymer in standard architecture were fabricated, the cell based on the polymer with 2-octyldodecyl side chain (P2) shows good photovoltaic performance with power conversion efficiency up to 0.47% and a high open circuit voltage of 0.96 V.

Graphical abstractPyromellitic diimide monomers with two different alkyl side chain substitutions were synthesized and used as electron-accepting units for preparing n-type conjugated polymers with benzodithiophene via Stille coupling reaction. These pyromellitic diimide-based polymers were used as acceptors, for the first time, for the construction of all-polymer bulk heterojunction solar cells with a standard architecture by using poly(3-hexylthiophene) as the donor. A high open circuit voltage of 0.96 V and a power conversion efficiency of 0.47% were achieved for the cell based on P3HT/P2.Figure optionsDownload full-size imageDownload as PowerPoint slide