Mechanical reliability of flexible perovskite solar cell

Abstract

The Sun is a sustainable, reliable and nearly infinite energy source, and photovoltaic energy is currently drawing attention as an alternative energy source. Organic-inorganic halide perovskite solar cells hold promise for next-generation photovoltaic devices due to their remarkable optical properties, high light-absorption coefficient and good cost-effectiveness, and the photovoltaic efficiencies of perovskite-based solar cells have rapidly soared from 3.8% to above 20%. In addition, perovskite devices have recently attracted substantial interest for flexible/stretchable electronic devices. In these various applications, especially flexible solar cells, one of the most important issues in device reliability and durability is mechanical properties. Most flexible perovskite solar cells are occurred degradation of photovoltaic properties after severe bending environment due to crack propagation on weakest layer in solar cell. However, it is unclear which mechanism is correct in fracture system. For this reason, estimation of mechanical properties in flexible perovskite solar cell is important. Researchers have used nanoindentation testing to study the elastic properties of perovskite-based solar cells. Unfortunately, the results of nanoindentation tests are strongly affected by the presence and makeup of the substrates, or under layers. For this reason, here we fabricated various free-standing component thin films of flexible perovskite solar cells using a simple solution process and transferred hole-substrates and evaluated their elastic deformation limits using nanoindentation on the hole-substrates. Hole size is proportional to the thickness of each thin film. We confirmed that the perovskite layer is by far the most fragile of all the components. Therefore, we evaluated and analyzed the intrinsic tensile properties of perovskite layers by an in-situ tensile testing system using push-to-pull devices. We believe that this study sheds light on the durability and fundamental mechanism of flexible perovskite solar cells.