Damage Behavior Of PET Film In Ozone/UV Environments And Its Effect On The Property Of α-Si Cell

Using a self-made environmental simulater of ozone﹠ultraviolet, the damage effects and mechanisms of PET films were studied in this paper. Afterwards, the electrical property of PET-encapsulated amorphous silicon solar cells was evaluated under O₃/UV environment.The results indicate that under exposal to ozone atmosphere, the mass of PET films tends to increase but the optical transmittance tends to decrease. This is due to the active chemi-absorption effect of ozone on PET. On the otherhand, vacuum ultraviolet﹠near ultraviolet radiation could result in mass loss and darkening in optical transportation of PET materials. FTIR, XPS﹠AFM analysis indicate high photon energy of ultraviolet ray could debond the C=O, C-O﹠ester groud, for using free radical﹠ finally leaving an etched rough surface. Comparitively, vacuum ultraviolet irradiation results in more mass-loss﹠optical darkening. This could be as a result from a stronger etching effect due to higher photon energy for vacuum ultraviolet ray in vacuum and a shielding effect of ozone induced by near-ultraviolet ray in ambient.As PET films expose to a sequential O₃/near-UV environment, the mass of PET shows gradually increase while the sample colour changes from white to yeallow one. Hence, the reason for this result is that a competitive effects of ozone active-absorption (resulting mass increase)﹠ultraviolet etching effect. However, under the synchronous exposure of O₃/UV environment, the PET mass increases linearly with the exposure time while its optical transmittance keeps almost no change. It is due to that a UV-enhanced surface absorption reaction of cause O₃ the mass increase while high-concentration O₃ in atmosphere shields the UV irradiation to etch the PET surface.Finally, the electrical properties were evaluated of the PET encapsulatedα-Si solar cell, under near-UV and O₃/near-UV exposure. An obvious degradation ofα-Si solar cell could be defected under near-UV irradiation, due to the optical darkening of PET encapsulate and Staebler-Wronski effect ofα-Si solar cells. However, under O₃/near-UV synchronous exposure, the cell property keep almost no change, because this environment shows almost no degradation of PET and weak Staebler-Wronski effect due to O₃ shielding effect.