• Jansen, Johan
• Durme, Kurt Van
• Ehrhardt, Dorothee
• Van Den Brande, Niko
• Mele, Bruno Van

Abstract

Typically, photovoltaic manufacturers guarantee a module lifespan of 25 years, during which photovoltaic modules must withstand the effects of outside conditions with limited performance reduction. However, daily thermal cycling and fast temperature changes cause thermal stresses between contiguous materials (due to mismatching thermal expansion coefficients), which lead to the formation of small fractures and cracks. By replacing conventional polymer layers used in photovoltaics by self-healing polymer materials, such micro-defects can be repaired before they increase in size and turn into larger defects, which may affect the energy output. Consequently, the sustainability of photovoltaics is increased.<br/>In this work, UV-crosslinked polymer networks containing reversible Diels-Alder bonds were developed to function as autonomously self-healing materials. It is shown by means of Fourier transform infrared spectroscopy, differential scanning calorimetry and dynamic mechanical analysis that these polymer networks have the potential to exploit the daily temperature cycle to achieve self-healing through thermally reversible chemical crosslinking, and that they maintain structural integrity over the whole photovoltaics application temperature range (-40 to 85 °C). These partially reversible Diels-Alder systems are able to heal at room temperature, which may even be in diffusion-controlled conditions (below their glass transition temperature). This means that even if the photovoltaic modules are exposed to moderate or cold outside temperatures during longer periods, the healing process within the self-healing polymer layers continues.

Topics

• impedance spectroscopy
• polymer
• glass
• glass
• crack
• glass transition temperature
• thermal expansion
• differential scanning calorimetry
• Fourier transform infrared spectroscopy
• dynamic mechanical analysis