Development of a New Time Resolved Irradiance Uniformity Mapper at Spasolab

Abstract

Irradiance uniformity mapping of solar simulators is a key characterization required for performing accurate solar cell electrical performance tests, alongside spectrum matching and stability. Within photovoltaic space standards such as [1] and [2], uniformity mapping is specified to verify the solar simulator nonconformance class. However, uniformity mappers are a relevant tool for solar simulator manufacturers as well as for space solar cell testing facilities, aiding to adjust test plane irradiance uniformity after maintenance, lamp replacement or on a more analytic approach, applying correction factors to the test plane. Thus, it is desirable to have a tool that allows for easier and faster acquisition of irradiance uniformity maps. This paper presents a time-resolved uniformity mapper developed at Spasolab based on two main premises: easy adaptability to different solar simulators and versatility in terms of irradiance operation range, extended up to 2 AM0. A modular two-stage design features independent bias PCB’s per each photodiode that allow for easy sensor swapping or different biasing for future sensor replacements. A new type of photodiode active biasing is also presented, with the main feature of being capable of switching on the bias voltage only during the acquisition process, hence reducing self-heating. Ad-hoc software developed in LabVIEW and PXI instrumentation enable the system to have different acquisition modes further expanding the irradiance range to be tested without risking hazard to the system due to overheating. Finally, outdoor calibration method and results for the system are also presented.