Perylene diimide based low band gap copolymers: synthesis, characterization and their applications in perovskite solar cells

Abstract

In this study, newly designed perylene diimide based polymers P1 and P2 were synthesized and were used as hole transporting materials in place of the more common spiro-OMeTAD in perovskite solar cells. The co-polymers P1-P2 were synthesized by Suzuki and direct arylation polymerizations of 2,9-bis(7-bromo-9,9-dioctyl-9H-fluoren-2-yl)anthra[2,1,9-def:6,5,10-d’e’f’]diisoquinoline-1,3,8,10(2H,9H)-tetrone M1 with 5,11-bis(2-hexyldecyl)-3,9-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,11-dihydoindolo[3,2-b]carbazole M2 and 3-octylthiophene M3, respectively. P1 and P2 exhibit broad absorption spectra in thin film and solution with the absorption extending from the ultraviolet to visible and near infrared region of the solar spectrum. The water contact angles of P1-P2 were determined to be 100.8° and 122.9°, respectively, showing good hydrophobicity for the synthesized copolymers. Both polymers show steady state photoluminescence quenching when blended with perovskite. Perovskite solar cell devices fabricated using P1-P2 in place of spiro-OMeTAD show power conversion efficiencies of 13.02% and 10.74%, respectively and manifest the potential of this class of materials as promising alternatives to conventionally used spiro-OMeTAD.