A New Quinoxaline and Isoindigo Based Polymer as Donor Material for Solar Cells: Role of Ecofriendly Processing Solvents on the Device Efficiency and Stability

A new semiconducting polymer based on two different electron deficient (quinoxaline and isoindigo) and electron rich (benzodithiophene) moieties is synthesized, characterized and used as donor material for photovoltaic devices. Blade-coated bulk heterojunction solar cells are fabricated in air by using chlorinated (o-dichlorobenzene) and non-chlorinated (o-xylene) solvents for the deposition of the active layer. The use of o-xylene allows a ~ 10% improvement of the device efficiency in comparison to the analogous system processed from o-dichlorobenzene. In addition, the evolution of the photovoltaic parameters of the resulting devices during thermal stress is monitored and compared, demonstrating a nearly identical resistance against temperature. The reported results not only highlight the promising properties of the new polymer in terms of environmental stability and compatibility with non-halogenated solvents, but also show an easy and ecofriendly way to further improve the device performance without altering the corresponding thermal stability.