New process boosts efficiency of bifacial CIGS thin film solar cell

Bifacial CIGS solar cells consist of very thin layers, only 3 µm in total for the active materials. Deposit-ed on top of a transparent electrical contact, the CIGS polycrystalline layer absorbs the light from both front and back sides. Image: Empa - Bifacial thin film solar cells based on copper indium gallium diselenide or CIGS can collect solar energy from both their front and their rear side - and thus potentially yield more solar electricity than their conventional counterparts. So far, however, their fabrication has led to only modest energy conversion efficiencies. An Empa team has now developed a new low-temperature production process resulting in record efficiencies of 19.8% for front and 10.9% for rear illumination. Moreover, they also produced the first bifacial perovskite-CIGS tandem solar cell, as recently published in Nature Energy, opening up the possibility of even higher energy yields in future. The idea is as straightforward as it is simple: If I can collect both direct sunlight as well as its reflection via the rear end of my solar cell, this should increase the yield of energy the cell produces.