Preparation and properties of nano zinc oxide doped ethylene vinyl acetate nanocomposites for solar cell encapsulation

Abstract

Long term stability of the encapsulant is needed to resist heat, moisture, ultraviolet (UV) light and other weathering stresses. In this study, a new way of improving the properties of ethylene vinyl acetate (EVA) encapsulant was reported by doping a very small quantity (0.05 wt%, 0.1 wt% and 0.15 wt%) of nano Zinc Oxide (n-ZnO). EVA/n-ZnO composites were made by solvent casting process with addition of surface modified n-ZnO, followed by compression moulding to achieve thin films with thickness of 0.4 mm to 0.5 mm. Then, the intrinsic EVA and EVA/n-ZnO nano-composites were characterized to check the electrical, thermal, mechanical, and optical properties. The nano-composites exhibited superior electrical insulation than the intrinsic one. High temperature electrical insulation was remarkably good for the nano-composites. The effect of n-ZnO was also prominent in the mechanical behavior of encapsulants; tensile strength increased from 3.7 MPa (for intrinsic EVA encapsulant) to 15.3 MPa (for 0.1 wt% nano-composite). Elongation at break was also increased for nano-composites. EVA nano-composites were able to maintain low dielectric constant and low dissipation factor even at elevated temperature. Another one important criteria is light (UV and visible) transmission through the encapsulant. UV and visible light transmittance spectrum of EVA nano-composites were found better than the commercially available encapsulant. Therefore, n-ZnO was successfully doped on to the EVA matrix to provide better electrical, thermal, mechanical, and optical properties even at elevated temperature.