Glass-Glass modules are gaining popularity for bifacial application and have believed advantages over PV modules with polymeric backsheets. Frameless glass-glass modules are promoted as PID-free, resistant to solvents, fire, and load stress, and capable of higher system voltages. We have found glass-glass modules run at higher operating temperature than Glass-Flex modules, and this reduces power output. Field power output results will be presented. Impermeable glass traps chemical byproducts, and faster power degradation from corrosion has been documented. Delamination has been observed in the field with glass-glass modules. A new accelerated test replicates this delamination. PID testing results will be presented comparing Glass-Glass and Glass-Flex modules.
Cu<sub>2</sub>ZnSn(S, Se)<sub>4</sub> (CZTSSe) is a promising alternative absorber material for thin-film photovoltaic applications because of its earth-abundant constituents, tunable band gap, and high optical absorption coefficient. Using binary and ternary chalcogenide nanoparticles as precursors we have developed a chemical route to produce high efficiency CZTSSe photovoltaic (PV) devices via solution based methods. The printed CZTSSe films show an interesting microstructure consisting of an upper micrometer-sized polycrystalline layer (large-grain layer) and a bottom fine-grain layer. In this paper, we present our results on characterization of the layers including composition, electronic and optical properties. Based on the observed properties we develop a numerical model for the CZTSSe PV device and present the simulation results. We anticipate that the combination of detailed characterization and device model will help us better understand the limitations of our current devices and indicate potential improvement paths.