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

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.

Automated summary

In this study, a non-contact electrostatic voltmeter technique is used to detect and map underperforming cells in photovoltaic modules. The technique directly maps the charged surface voltage of the glass and shows good agreement with voltmeter values obtained by other methods. The combination of electrostatic voltmeter and electroluminescence techniques allows for quantitative spatial mapping of defects. This work holds promise for detecting underperforming modules in solar PV power plants.