UV-curable self-healing polymer layers for increased sustainability of photovoltaics

Description

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.
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, (modulated temperature) 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). Recently, room-temperature healing of a fully reversible Diels-Alder system based on furan and maleimide was reported, proving that elevated temperatures are not always required for self-healing. [1] Additionally, it was recently shown on a similar system that the Diels-Alder reaction continues in diffusion-controlled conditions (below the glass transition temperature). [2] 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.

[1] M. M. Diaz, J. Brancart, G. Van Assche, and B. Van Mele, “Room-temperature versus heating-mediated healing of a Diels-Alder crosslinked polymer network”, Polymer, vol. 153, pp. 453–463, 2018.
[2] D. Ehrhardt, J. Mangialetto, R. Verhelle, J. Brancart, B. Van Mele, N. Van den Brande, K. Van Durme, J. Jansen, " The Effect of Vitrification on the Diels-Alder Reaction Kinetics", Central and Eastern European Committee for Thermal Analysis and Calorimetry (CEEC-TAC), p. 368 PS2.002, ISBN 978-3-940237-50-7.

Periode	5 jun 2019
Evenementstitel	7th International Conference on Self-Healing Materials (ICSHM2019)
Evenementstype	Conference
Locatie	Yokohama, Japan
Mate van erkenning	International