Optimisation of the I-V measurement scan time through dynamic modelling of solar cells

Abstract

High-performance solar cells and photovoltaic modules exhibit high internal capacitance, limiting the speed of their transient responses including the current-voltage characteristics scans. This study proffers a model-based method to obtain optimal scan time during the current-voltage performance characterisation of a solar cell or module while preserving a pre-set accuracy. Static model parameters are extracted from the quasi-static current-voltage characteristic, whereas the capacitive character, modelled by two bias voltage dependent capacitances, is determined from the open-circuit voltage decay measurement. The obtained model is used to calculate the optimal current-voltage curve scan time. Efficacy of the proposed method is demonstrated through test results obtained on three wafer-based solar cells. I-V curve errors determined by the proposed method at different scan times are in good agreement with the measurements. Results show that in order to achieve < 0.5% error in curve fitting, determined scan times of tested crystalline silicon solar cells lie within the range of 3.6-45 ms for constant angle step semiconductor curve tracer. Use of a capacitive-based curve tracer, however, requires approximately twice that time to retain a comparable error. © 2013 The Institution of Engineering and Technology.