| This work explores the relationship between basic solar-cell parameters and carrier-trapping states within several categories of CuIn1-x Gax(Se1-ySy)2 (CIGS) solar-cell devices. Some devices were produced by evaporation, and some by selenization of metal films.; Although there are numerous ways in which the devices studied can be categorized, three sets of general experimental trends were noted, two of which are mentioned here. One set of comparisons was made between all evaporated and all selenized devices. One other set of trends was observed when comparing all selenized devices to each other.; Comparisons between evaporated and selenized devices yielded several strong trends. The evaporated devices tend to have higher open-circuit voltages (VOC), lower defect activation energies, and significantly fewer defect states detected near the interface than the selenized devices. Admittance spectroscopy results imply that the overall defect density of the evaporated devices is lower.; Within the group of selenized devices, a higher trap density deduced from drive-level capacitance profiling appears to modestly correlate with a higher VOC. This correlation suggests that the majority of the detected traps do not participate in recombination that limits the performance of the devices. Thus, the detected traps may be affecting a device much like non-frequency dependent shallow acceptor levels. This must now be put in perspective with the aforementioned observations comparing evaporated and selenized devices. Based on VOC, it does not appear that the best selenized devices have the lowest trap density. Thus, although the selenized devices do have a higher trap density than the evaporated devices, the overall number density of shallow traps may not be the reason the selenized devices do not perform as well as the evaporated devices, rather merely the presence of a measurable density of defect states near the interface may be the reason for the performance difference. |
