Photovoltaic performance optimization of methyl 4-[6,6]-C61-benzoate based polymer solar cells with thermal annealing approach

• Methyl 4-[6,6]-C61-benzoate (MCB) is a good n-type material as the alternative of PCBM.
• We study the effect of annealing temperature on P3HT and MCB devices.
• The ideality factor and the reverse saturation current density are used to explain the device performance variation.

A new type of fullerene acceptor, methyl 4-[6,6]-C61-benzoate (MCB), was used to fabricate bulk heterojunction solar cells in combination with poly(3-hexylthiopene) (P3HT) as donor. To optimization of device performance, the effect of annealing temperature was investigated in the range of 80–180 °C. And the highest power conversion efficiency (PCE) of 3.49% was achieved after baking the device at 110 °C for 10 min. This optimization condition was associated with the surface morphology of blend films as investigated by atomic force microscope and optical microscope. The device parameters were also analyzed by the relationship among the open circuit voltage, the short circuit current density, the reverse saturation current density and the ideality factor. Moreover, the devices were stable and the PCE showed about 90% durability even after 72 days.

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