Expanded experimental space for luminescence studies of thin film CdS/CdTe solar cells

We have explored a large range of experimental space for photoluminescence (PL) and electroluminescence (EL) measurements of CdS/CdTe solar cells. This space includes changes in temperature, injection intensity (laser power for PL, current for EL), electrical bias for PL, and laser energy for PL. Measurements were resolved both spectrally and spatially (2D for EL, 1D for PL). Combination of EL and PL measurements revealed that most spatial inhomogeneity was the result of non-uniform current transport rather than local variations in recombination rate. The greatest spectral resolution was obtained with low temperature EL at low injection rates. High injection EL as well as high forward biased PL suppressed band-edge emission at low temperatures. Spectral structure was found to be greater in EL than in PL. These effects likely originated from preferential current transport along grain boundaries and/or certain grains.