Novel unsymmetrical squaraine-based small molecules for organic solar cells

Abstract

A new unsymmetrical squaraine dye (USQ) series for organic solar cells (OSC) is synthesized by a simple route without using highly toxic reagents. These USQs exhibit a low bandgap of 1.57 eV and HOMO energies of ∼−5.2–5.3 eV. Despite the very simple molecular structures, OSC devices based on these USQs exhibit an impressive open-circuit voltage of 0.92 V and power conversion efficiencies (PCEs) approaching 5%, achieved without using any additives or post film deposition treatment. The results indicate that USQs are promising materials for sustainable energy applications.