Bulk And Interface Characterization And Modeling Of Copper Indium Aluminum Gallium Selenide (Ciags) Solar Cells

The saturation of V-OC at larger band gaps in Cu(In,Ga)Se-2 devices presents a major challenge in developing high efficiency solar devices for tandem solar applications. Although recent studies have shown that recombination at the buffer/absorber interface dominates in high Ga samples with wide band gaps, the interface parameters are not well understood to accurately model the device behavior. In this work we have applied temperature dependent CV and DLCP methods to estimate the interface state density along the bandgap in CIGS and CIAGS based solar devices. We have also used DLTS to study the nature of deep levels in CIGS and CIAGS devices. Based on our analysis and device simulation results, we attribute the VOC saturation in wide gap CIAGS devices to increased recombination rate at the interface.