In situ monitoring of photovoltaic properties in organic solar cells during thermal annealing

This paper reports a simple and useful technique that monitors the changes of poly(3-hexylthiophene) (P3HT):1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61-based organic solar cells (OSCs) during thermal annealing in situ. Thermal annealing was divided into five stages in which the variations of the cell parameters were obtained in detail. Annealing temperature that was higher than the glass transition temperature of P3HT (127 °C) was found critical to the improvement of open-circuit voltage. The initial rise of the short-circuit current was explained by in situ monitoring of the transport behaviors of electrons and holes. Finally, in situ monitoring was adopted to compare OSCs that were or were not solvent-annealed, indicating the effectiveness in optimizing, modeling and understanding in depth the effects of the thermal annealing of OSC with a blended active layer.

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► In situ measurement of organic solar cells during thermal annealing.
► Open-circuit voltage has an obvious turning point at ∼140 °C.
► Effects of thermal annealing on organic solar cells were revealed in detail in five stages.
► Direct observation of cell parameters of blended organic solar cell.
► Devices with and without solvent annealing were compared.