Hotspot analysis on a flexible PV mini-modules based on IBC solar cells

The photovoltaic market is dominated by crystalline silicon (c-Si) panels; however the low load-bearing capacity of some buildings and specific surface design constraints make this technology not suitable for every application. Flexible crystalline-silicon photovoltaics (Fc-SiPV) recently attracted attention, enabling operation in contexts where light weight and bendable nature can be desirable such as BIPV (building-integrated photovoltaics), off-grid applications, solar-powered vehicles/boats and portable electronics. However, the bending of the modules can induce cracks which ultimately compromise the overall efficiency and long-term reliability. In this study, hotspots induced by cracks are investigated through EL (electroluminescence) and IR (infrared) thermography techniques performed both indoor and outdoor. The study is carried out on a flexible module made of four IBC Si cells, laminated with a plastic encapsulant. From the module characterization, a mismatch between cells emerged: cells 2 and 3 exhibit lower efficiencies (15.30% and 16.58% respectively) compared to the best performing cell (18.01%). Thanks to EL investigations, cracks were identified as the main cause for the worsening of some cell’s performance; by IR imaging, the local temperature increase was measured. Finally, it was possible to quantify how much power is dissipated in a single cell due to cracks, by measuring the voltages at the single cell’s terminals. These results underline the necessity to examine the effects of cracks in flexible modules, which cause local heating, possibly leading to critical temperatures for the lamination and inducing significant power losses. Based on these results, future studies will focus on optimizing the lamination process by analyzing the effects of different lamination steps on cracks formation, including encapsulation temperature, velocity and pressure by applying the same monitoring techniques as previously discussed.