High-Efficiency Polymer Solar Cells Enhanced by Solvent Treatment

A significant enhancement of efficiency in thieno[3,4‐b]‐thiophene/benzodithiophene:[6,6]‐phenyl C71‐butyric acid methyl ester (PTB7:PC70BM) solar cells can be achieved by methanol treatment. The effects of methanol treatment are shown in an improvement of built‐in voltage, a decrease in series resistance, an enhanced charge‐transport property, an accelerated and enlarged charge extraction, and a reduced charge recombination, which induce a simultaneous enhancement in open‐circuit voltage (Voc), short‐circuit current (Jsc), and fill factor (FF) in the devices.