This research poster presentation summarizes an experiment investigating the effect of solvent composition on polythiophene solutions. Polythiophene derivatives P3HT, P3OT, and P3BT were dissolved in chloroform (a good solvent) and varying amounts of bad solvents like acetone were added. The absorption and photoluminescence spectra of the solutions were measured. The results show that increasing bad solvent content induces formation of polythiophene aggregates, shifting absorption peaks to lower wavelengths. P3HT formed aggregates at the lowest acetone content while P3OT required the most acetone before aggregating.