Outdoor ageing of the dye-sensitized solar cell under different operation regimes

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• The dye-sensitized solar cells (DSSCs) have been aged outdoor for seven months.
• The influence of different operating regimes (open circuit, short circuit and maximum power point regimes) on degradation is presented.
• Two practical solutions for outdoor ageing of laboratory size DSSCs in maximum power point regime are presented and compared.
• The evolution of spatial defects upon outdoor ageing has been tackled with electroluminesce and optical transmittance imaging.
• A new phenomenon related to the healing effect of DSSC realized by thermal annealing is demonstrated for the first time.

Ionic liquid based dye-sensitized solar cells (DSSCs) were exposed to outdoor irradiation for seven months (April-October, 906 kWh/m2, latitude 46°2'39.39"N, longitude 14°29'18.28"E) under short-circuit, open-circuit, and quasi maximum-power-point regime. As a reference we kept a series of DSSCs in the dark at room temperature under open-circuit regime. The performance of the DSSCs was evaluated indoor under standard test conditions prior to ageing, twice during ageing and after ageing. Additionally, the electroluminescence and transmittance imaging were used to follow the evolution of local defects with ageing. Operating regime has a strong influence on the ageing of DSSCs but despite this the performance of DSSCs remained remarkably stable. The exceptions were cells aged under short-circuit regime, which led to a significant decrease in JSC. This resulted from the degradation of the dye molecules and a decrease in the tri-iodide concentration in the electrolyte.