Evaluation of micro- and nanoscale uniformity in all-PVD Cu(In,Ga)Se2 solar cells

Over the past several years, advances in manufacturing for thin film Cu(In,Ga)Se₂ (CIGS) devices have enabled volume production of high efficiency solar material with good repeatability and uniformity. In this study, quantitative analysis of several advanced imaging techniques was used to evaluate the uniformity of electronic properties for all-PVD CIGS solar cells. Combined EL and DLIT analysis suggests that series resistance in the top electrode constitutes the strongest nonuniformity, which is estimated to contribute about 2.5% relative efficiency loss. High-resolution EL image analysis shows a highly uniform lateral band gap distribution with standard deviations of minimum band gap values <;2 meV. Finally, EBIC image analysis shows collection lengths of 1.5 ± 0.2 μm, indicating high collection probability throughout the depth of the CIGS absorber layer and at grain boundaries. Highly uniform micro- and nanoscale electronic properties have enabled all-PVD CIGS solar modules to reach a certified efficiency of 15.7% over 0.97 m² aperture area.