Bergqvist, J.Lindqvist, C.Backe, O.Ma, Z.Tang, Z.Tress, W.Gustafsson, S.Wang, E.Olsson, E.Andersson, M.R.Inganas, O.Müller, C.2025-12-172025-12-172014Journal of Materials Chemistry A, 2014; 2(17):6146-61522050-74882050-7496https://hdl.handle.net/11541.2/115214Thermal annealing of non-crystalline polymer:fullerene blends typically results in a drastic decrease in solar cell performance. In particular aggressive annealing above the glass transition temperature results in a detrimental coarsening of the blend nanostructure. We demonstrate that mild annealing below the glass transition temperature is a viable avenue to control the nanostructure of a non-crystalline thiophene–quinoxaline copolymer:fullerene blend. Direct imaging methods indicate that coarsening of the blend nanostructure can be avoided. However, a combination of absorption and luminescence spectroscopy reveals that local changes in the polymer conformation as well as limited fullerene aggregation are permitted to occur. As a result, we are able to optimise the solar cell performance evenly across different positions of the coated area, which is a necessary criterion for large-scale, high throughput production.enCopyright 2014 Royal Society of Chemistrybulk-heterojunction solar cellsHOMOLUMOoptical absorptionpolyfluorenesJournal article10.1039/c3ta14165a2-s2.0-84897555619