Tuning Thin Film Properties by Structural Modulations in Red Fluorescent Protein Chromophore Analogues

Abstract

The study of the role of substituents present in molecules is extremely important for designing new functional materials. In the present study, we have designed and synthesized four analogues (AR1‐AR4) of the red fluorescence protein (rfp) chromophore by varying the substituents and have studied their thin film properties by fabricating opto‐electronic devices with them. Molecules AR1 and AR2 were designed with improved donor‐acceptor (D−A) properties. Molecule AR3 was synthesized with an increased vinyl conjugation and molecule AR4 had an extra fluorescent moiety in the conjugation. The orbital levels and optical energy gap were estimated theoretically by density function theory. The optical absorption in solution/thin films, quality of film formation and the electrical charge transport mobility in films were studied. Photovoltaic parameters of bulk heterojunction solar cell devices formed with the four molecules were then determined. Interestingly, molecule AR3 with the extra vinyl conjugation was found to be the best of the four molecules reported here for application in organic electronics. The extra vinyl conjugation improved the π‐π stacking and helps to form smoother films with increased optical absorption and a desirable hole mobility.