Fatigue crack growth in perovskite in cyclic bending

Organic-inorganic hybrid perovskite materials have been widely used in the field of photovoltaics due to their excellent advantages such as high color purity with a narrow full-width at half maximum, high charge carrier mobility, tunable optical bandgap, and low-cost solution-based processing. Recently, many researchers have reported deformable perovskite LED, since the demand for flexible and stretchable electronics increases. Although flexibility of perovskite LED has been determined mainly through empirical methods, flexibility of perovskite materials in LEDs has not been studied systemically. Since LEDs are manufactured in the form of multilayer structure with various constituent materials in thin films, compressive and tensile strain are varies depending on the distance from neutral axis under the bending stress. It is important to measure mechanical properties and analyze fatigue resistance for perovskite, which is the weakest material in LED, because a fracture will occur at this point. In this work, fatigue resistance of perovskite materials was evaluated by crack propagation mechanism. We prepared samples for mechanical testing with different microstructure by same procedure for manufacturing perovskite LEDs. Mechanism of fatigue crack propagation in perovskite materials was evaluated by measured crack nucleation and propagation every several hundred-bending cyclic under various bending strain. We compared mechanism of fatigue-crack propagation with mechanical behavior as determined by uni-axial tensile test in SEM. We evaluated suitable microstructure for flexible perovskite LED by fatigue resistant of perovskite materials