Low-boiling-point solvent additives can also enable morphological control in polymer solar cells

•We utilize low-boiling-point solvent additives to improve morphology of polymer solar cells.•Utilizing a low-boiling-point additive tetrahydrofuran resulted in better charge extraction.•Additive led to polymer-fullerene demixing and lower leakage currents.•Effect was largely insensitive to slight variations in boiling point and solvent's dipole moment.•Effect appears to be general to more material systems.

Processing organic photovoltaic (OPV) blend solutions with high-boiling-point solvent additives has recently been used for morphological control in bulk-heterojunction OPV cells. Here we show that even low-boiling-point solvents can be effective additives. When P3HT:PCBM OPV cells were processed with a low-boiling-point solvent tetrahydrafuran as an additive in parent solvent o-dichlorobenzene, charge extraction increased leading to fill factors as high as 69.5%, without low work-function cathodes, electrode buffer layers or thermal treatment. This was attributed to PCBM demixing from P3HT domains and better vertical phase separation, as indicated by photoluminescence lifetimes, hole mobilities, and shunt leakage currents. Dependence on solvent parameters and applicability beyond P3HT system was also investigated.

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