Organic Solar Cells for Indoor Applications
Comparing efficiencies of solar cells for indoor applications is challenging due to the variety of light sources and lack of standards. Lübke et al. show a solution to this problem that allows comparison of data measured with a variety of different light sources.
The internet of things requires a variety of different sensors to be continuously powered to retain their ability to record and transmit information in an industrial environment. Ideally the sensors should operate without the need to constantly change a battery. One possible solution are organic solar cells which have the advantage of their adaptability to various light sources. While white LEDs are becoming the most important light source for indoor applications, their light spectrum varies greatly. Thus, comparing power output and efficiencies of solar cells for indoor applications also vary depending on the used LED. In order to still be able to compare performances with each other and decide which are the most promising materials for further investigation, one needs either standard testing conditions for indoor applications (in a similar way as established for outdoor illumination) or alternatively a way of comparing performances measured with different light sources. Here, we present an approach based on the second concept. By using measured external quantum efficiencies and current-voltage curves measured under one light source, Lübke et al. calculate the performance of the solar cell under any light source at a given irradiance. Furthermore, they compare the achieved performance with the fundamental limits of performance based on thermodynamic arguments.
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