A self-calibrating led-based solar test platform

A compact platform for testing solar cells is presented. The light source comprises a multi-wavelength high-power LED (light emitting diode) array allowing the homogenous illumination of small laboratory solar cell devices (substrate size 50 x 25 mm) within the 390-940 nm wavelength range. The spectrum can be synthesized by independent tuning of the 18 different wavelengths to mimic AM 1.5G as well as various indoor lamp spectra. The intensity can be controlled with a 2(14)-bit accuracy and intensities up to 3 suns are possible with an approximate AM 1.5G spectral distribution. For several wavelengths intensities up to 10 suns is possible, and for a few wavelengths up to 30 suns can be reached. The setup is equipped with reference diodes and an optical fibre coupling enabling calibration, monitoring and control of the light impinging on the sample. Through a computer controlled interface, it is possible to perform all the commonly employed measurements on the solar cell at very high speed without moving the sample. In particular, the LED-based illumination system provides an alternative to light-biased incident photon-to-current efficiency measurement to be performed which we demonstrate. Both top and bottom contact is possible and the atmosphere can be controlled around the sample during measurements. The setup was developed for the field of polymer and organic solar cells with particular emphasis on enabling different laboratories to perform measurements in the same manner and obtain a common basis for comparing data. The use of the platform is demonstrated using a standard P3HT:PCBM polymer solar cell but is generally applicable to any solar cell technology with a spectral response in the 390-950 nm region. Copyright (C) 2010 John Wiley & Sons, Ltd.