• 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<br/>withstand the effects of outside conditions with limited performance reduction. However, daily thermal cycling and fast<br/>temperature changes cause thermal stresses between contiguous materials (due to mismatching thermal expansion<br/>coefficients), which lead to the formation of small fractures and cracks. By replacing conventional polymer layers used in<br/>photovoltaics by self-healing polymer materials, such micro-defects can be repaired before they increase in size and turn<br/>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<br/>autonomously self-healing materials. It is shown by means of Fourier transform infrared spectroscopy, (modulated<br/>temperature) differential scanning calorimetry and dynamic mechanical analysis that these polymer networks have the<br/>potential to exploit the daily temperature cycle to achieve self-healing through thermally reversible chemical crosslinking,<br/>and that they maintain structural integrity over the whole photovoltaics application temperature range (-40 to 85 °C).<br/>Recently, room-temperature healing of a fully reversible Diels-Alder system based on furan and maleimide was reported,<br/>proving that elevated temperatures are not always required for self-healing. [1] Additionally, it was recently shown on a<br/>similar system that the Diels-Alder reaction continues in diffusion-controlled conditions (below the glass transition<br/>temperature). [2] This means that even if the photovoltaic modules are exposed to moderate or cold outside temperatures<br/>during longer periods, the healing process within the self-healing polymer layers continues.<br/>[1] M. M. Diaz et al., Polymer, vol. 153, pp. 453–463, 2018.<br/>[2] D. Ehrhardt et al., Central and Eastern European Committee for Thermal Analysis and Calorimetry (CEEC-TAC), p.<br/>368 PS2.002, ISBN 978-3-940237-50-7.

Topics

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