Quantitative imaging of shunts in organic photovoltaic modules using lock-in thermography

Abstract Thermographic methods are widely established to detect shunts in photovoltaic technologies. In all methods the cell has to be directly accessible to determine quantitative shunt values. In this manuscript a precise method is presented to determine shunt values in solar modules consisting of series connected bulk-heterojunction organic solar cells without the need to access the single cells separately. It will be shown that, although parallel resistances in organic solar cells show a strong dependence on the illumination intensity, the shunts that are detected using illuminated lock-in-thermography are strongly ohmic and therefore can be assigned a distinct ohm value.