Tensile test of Indium Tin Oxide (ITO) deposited on polyerhylene naphthalate (PEN) films used in solar cells were carried out. It was found from tensile tests that many AE signals were detected in ITO films. On the other hand, the electric resistance of ITO + PEN film was also measured later than first AE signal during tensile tests. In order to identify AE sources, in-situ observation of specimen and measurement of electricity resistance were also carried out. It was demonstrated that AE behavior shows good agreement with the cracking behavior in ITO. In addition to it, AE monitoring could be detected damages in ITO under mechanical strain earlier than were measurement of electricity resistance. Consequently, it was suggested that AE technique was extremely effective technique for damage detection and evaluating the damage accumulation process in films used in solar cells.
