Approaching highly stable optoelectronic device operation at elevated temperature by locking backbone torsion of conjugated polymers

Abstract

The ability of organic electronics to maintain stability at elevated temperatures is crucial for the longevity of optoelectronic devices. However, achieving stable optoelectronic properties for conjugated polymers remains fundamentally challenging. Here, we identify backbone twisting motion as the primary reason for the unstable optoelectronic properties of donor-acceptor (D-A) conjugated polymers, using diketopyrrolopyrrole (DPP)-based polymers as a model system. The backbone thiophene-ring twist transition is responsible for shifts in the band gap and alterations in charge transport properties. The twisting motion of the thiophene induces localization of the intrachain electrons, resulting in reduced charge carrier mobility and a significant blue shift in optical absorption. Additionally, we demonstrated that intramolecular hydrogen bonding interaction within DPP polymers can suppress undesired backbone twisting at elevated temperatures, thereby ensuring a more stable optoelectronic property. Our work offers fundamental insights into the decline in device stability at elevated temperatures and a strategy to enhance device stability.