Photovoltaic performance of novel push–pull–push thienyl–Bodipy dyes in solution-processed BHJ-solar cells

Abstract

This work explores the synthesis of extended dipyrromethene dyes engineered from thiophene-linked triphenylamine modules in order to favor pronounced charge transfer within the dyes and to enable their use in solar cells. We found that these soluble dyes absorb up to 760 nm in solution and 850 nm in thin films. An effective charge transfer absorption band was found at around 460 nm. In the crystal lattice, molecules are organized in layers separated by 3.50 Å with pronounced π–π stacking and S⋯S interactions. The electroactivity of the dyes indicates that electron injection in PC₇₁BM is feasible. Bulk heterojunction solar cells based upon dyes 1 and 2 in an optimized device structure ITO/Ca/1 or 2:PC₇₁BM/MoO₃/Ag provide a power conversion efficiency of about 1.5% after thermal annealing.