Study of thin-film silicon solar cells at irradiances above ten thousand suns

We used a tightly focused Gaussian beam of a HeNe laser to study accelerated light-induced degradation (Staebler-Wronski effect) and high photocarrier generation rates in amorphous and microcrystalline silicon thin-film solar cells, at up to13 MW/m(2) irradiance. For the experiments, the spot radius was varied from a minimum of 8.6 mu m in the focus to around 1 mm away from the focus. According to COMSOL (R) simulations, even at these high power densities heat diffusion into a glass substrate aided by spreading conduction via the Ag back-contact restricts the temperature rise to less than 14 K. Short-circuit current can be measured directly over a range of irradiances, and the J-V characteristic may be estimated by taking into account shunting by the inactive part of the cell.