Implied J-V Curves Recorded at Elevated Temperatures Using Light Controlled Heating

Abstract

The carrier lifetime characterization of solar cells is typically performed at room temperature, although the operational temperature of a solar panels can reach 60 °C. We realized a setup for laser controlled photoconductance decay (PCD) measurement at elevated temperatures induced by light. We investigated precursor p-PERC cells from multiple parts of the same ingot using this technique. From the injection level dependent carrier lifetime results the implied current-voltage characteristics are evaluated as well. We observed a relatively small but noticeable increase of the carrier lifetime up to 30% with increasing the temperature from 30°C to 60°C in all samples. Saturation current values obtained using the Kane-Swanson method indicate, that not only the bulk lifetime improves but the surface recombination rate weakens. Temperature coefficient values of the implied cell efficiency are around -0.35 rel%/°C and slightly below which agrees with typical results of electrical tests. However, due to the minor increase of the carrier lifetime, this is still a bit above the value one can obtain  theoretically considering purely the known decrease of the open circuit voltage caused by the increased intrinsic charge carrier concentration at higher temperatures.