Novel unsymmetrical squaraine-based small molecules for organic solar cells

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. New unsymmetrical squaraines for organic solar cells (OSCs) are synthesized without using highly toxic reagents. OSCs based on these squaraines exhibit an impressive open-circuit voltage of 0.92 V and power conversion efficiencies approaching 5%.