Synthesis of Highly Photostable Benzoindolenine‐Based Squaraine Dyes by using Aromatic Fluorine Atoms

Abstract

We have elucidated the details of the photodegradation of non‐fluorinated benzoindolenine‐based SQ dyes with low photostability in solution and proposed a hypothesis to improve their photostability. Based on the results, replacing all the hydrogen atoms on the benzoindolenine ring with fluorine atoms or methylation of the oxygen anions of the non‐fluorinated benzoindolenine SQ dye resulted in improvement of photostability. Furthermore, a preliminary investigation of the synthesized SQ dyes for organic photovoltaics revealed that the O‐methylated SQ dye with bulky fluorine‐containing anions provided a much higher Voc than similar benzoindolenine‐based SQ dyes.