PV performance measurement algorithms procedures and equipment

The voltage bias rate, the bias direction, the premeasurement conditions, and the spectral irradiance of the light source all have an effect on the measured current versus voltage (I-V) characteristics of a photovoltaic (PV) device. These effects are quantified for a variety of different device structures. Algorithms for determining the maximum power point are compared for several devices using the same data acquisition system. The effects of voltage bias rate and direction on the I-V characteristics are quantified for several different material systems. It is pointed out that often these effects are not documented in the reporting of the I-V characteristics, and the most favorable premeasurement conditions are used instead. The I-V characteristics of two-terminal tandems are a function of the light source. Procedures have been adopted by several groups that allow the I-V characteristic of any tandem structure to be determined with respect to a fixed set of reference conditions. The algorithm used to determine the maximum power can affect the performance, causing an unrealistically high or low efficiency