Improving structural order for a high-performance diketopyrrolopyrrole- based polymer solar cell with a thick active layer

A series of low-bandgap polymers based on thienyl benzodithiophene (BDTT) and furan-substituted diketopyrrolopyrrole (FDPP) units with different side chains are presented. By replacing the branched ethylhexyl group on the FDPP unit with linear side chains, the structural order and carrier mobility of the modified polymers are enhanced accordingly. The power conversion efficiencies (PCE) of single-junction devices based on polymers of this series are improved from ≈5% to ≈7%. More importantly, devices made from the modified polymers show excellent photovoltaic performance with a thick active layer of up to 360 nm, a very promising characteristic for the industrial implementation of polymer solar cell devices. By replacing branched side chains with linear side chains, a polymer system used in solar cells acquires enhanced structural order and carrier mobility. The power conversion efficiences (PCEs) of single-junction devices incorporating these polymers are improved from ≈5% to almost 7%, and the devices based on the polymers containing linear side chains show excellent photovoltaic performance with a thick active layer of up to 360 nm, making them promising for industrial implementation. KGaA, Weinheim.