Packaging Flexible Perovskite Solar Cells to Withstand Accelerated Stress Testing

Perovskite solar cells have emerged as promising low-cost and efficient alternatives to silicon. Unlike conventional silicon cells, which are relatively thick and rigid, perovskite devices can be made on lightweight, flexible substrates that can conform to different surfaces in a variety of applications. However, proper encapsulation is essential to protect solar cells from environmental stresses and to ensure long lifetimes. Packaging is especially important for perovskite materials—in particular low-gap perovskites used in all-perovskite tandems—because they are sensitive to moisture and oxygen. Compared to glass, common flexible polymer substrates, such as PET, have much higher water vapor transmission rates (WVTR). An additional moisture/oxygen barrier layer is thus needed to protect flexible perovskite devices. While commercial packaging solutions have been optimized for silicon solar cells, there have been far fewer studies encapsulating perovskite solar cells deposited on flexible substrates.<br/><br/>Here, we discuss the details of the processes we find important in successfully packaging flexible perovskite solar cells to achieve an environmentally robust flexible package. We find that the following factors contribute strongly to an effective packaging strategy: intrinsic perovskite stability, proper substrate handling, adhesion of films to flexible substrates, and compatible lamination materials and conditions. In this talk, we discuss optimization of processes that are designed with careful consideration of materials and parameters. This enables flexible packaged tandem perovskite devices that can withstand stress testing of 1000 hrs at 85 °C/85% relative humidity as well as 200 thermal cycles from -40 °C to 85 °C. These results are an important step toward enabling flexible perovskite solar cells to be deployed in residential and commercial applications.