Solar Cell Performance Measurements Under Artificial Lighting Sources

In recent years, there has been a growing interest in measurements of photovoltaic solar cells under ambient artificial lighting such as light emitting diode (LED) or fluorescent light sources. Certain classes of solar cells are considered very good candidates for energy harvesting from mostly visible ambient lighting for the purpose of powering internet-of-things devices. However, measurements of the irradiance of these light sources, a key requirement for characterization of solar cells, has been challenging because there are currently no reference solar cells offered by any metrology laboratory for low light artificial measurements. The current approach of using illuminance meters for measuring the irradiance can result in unacceptable discrepancies between different labs. In this work, we take the first steps in demonstrating that a reference solar cell can indeed be calibrated under a well-defined low-light spectrum and can be used to perform current vs. voltage measurements on any test device under any arbitrary low light spectrum yielding consistent results. This work also highlights the pitfall of using lux meters for measuring light intensity and instead advocates for use of an effective irradiance ratio.