Voltage mapping and local defects identification in solar cells using non-contact method

Abstract

Electroluminescence, infrared imaging, and current–voltage curve techniques are used to detect and map underperforming cells in a photovoltaic module or the modules in a photovoltaic string. In this work, we present a non-contact electrostatic voltmeter technique to detect and map the underperforming spots in a cell and the cells in a module. This non-contact technique directly maps the charged surface voltage (671 mV) of the superstrate glass, and it had an 11-mV difference with the voltmeter values (660 mV). Another data set of voltage values obtained by electroluminescence images conversion into a voltage map showed a difference of 7 mV with the non-contact voltmeter values. The direct voltage values obtained at various good and poor-performing spots of the cells using this technique are 3.69 V and 3.79 V and are validated using the voltage values obtained in electroluminescence analysis and the difference in voltage obtained by the two techniques is determined to be less than 2%. In this work, we combine the strengths of two complementary techniques of the electrostatic voltmeter (strength: quantitative) and electroluminescence (strength: spatial mapping) to obtain a quantitative spatial mapping of defects. Furthermore, this work is extendable to detect the poor-performing modules in solar PV power plants.