Commercial Photodiode Suitability for Solar Simulator Light Monitoring

Abstract

The use of commercially available photodiodes for developing diverse solar simulator light monitoring applications is a very convenient approach due to availability, quality, performance and cost effectiveness. Photodiodes as light monitors are meant to be operated in constant current zone, commonly referred to as photoconductive mode. In this operation mode, they offer linear response to impinging light over a few orders of magnitude. However, while presenting desirable characteristics in the manufacturer’s specification sheets, there is a general lack of information regarding current response saturation for higher irradiances as it is the case of placing the photodiode directly under AM0 like conditions leading to possible misuse. This paper will provide a guided approach on how to determine photodiode eligibility for solar simulator light monitoring applications. Needing to be linear around AM0 irradiances, suitability will rely on empirical IV tests at different irradiation conditions of three commercial silicon photodiodes performed in one of Spasolab’s Xe based solar simulators. Further testing data including spectral response will also be provided from a specially manufactured off the production line photodiode from Hamamatsu, which has never been published, proving it to be an excellent option. Test data will serve to give guidelines on suitability for the application focusing on series resistance, having enough reverse bias headroom and containing power consumption to avoid excessive self-heating, yielding an appropriate bias voltage to assure linearity. Finally, a discussion on the photodiode’s upper saturation limit determination will be introduced.