Reliability of thin films for solar photovoltaic applications

Degradation of the solar cell over the time under different mechanical and loading during the manufacturing or use is one of the most common problems in the solar industry. One of the major reasons for this degradation is the cracks and/or film damage of one of the conductive layers, (i.e., front electrode and back electrode). The primary objective of this research is to investigate the behavior the front and back electrodes under different mechanical and environmental loads. Therefore, bending fatigue, stretching, thermal aging, thermal cycling and damp heat experiments were conducted on Indium tin oxide (ITO), aluminum doped zinc oxide (AZO) and aluminum thin films that deposited on different substrate, such as Polyethylene terephthalate (PET), cardinal glass, and silicon wafer. The electrical resistance was monitored during the application of mechanical and thermal loads to see the pattern of relationship between the load and the electrical continuity as a consequent of failure. Moreover, the cracks init iation and preparation were monitored during the cyclic bending fatigue and stretching experiments. Finally, after completing the environmental loading experiments (i.e., thermal aging, thermal cycling and damp heat), scanning electronic microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and film transmittance tests were conducted on the as-produced, tested samples to show the effect of the environmental condition on the material property. SEM images were obtained to observe the surface morphology change, EDAX was conducted to monitor the film composition change, and XRD was performed to study the change in the material crystallinity. Change in the transmittance of the films was tested as well.