Encapsulation Films for Silicon Solar Cells: Multifunctional Polyolefin Elastomeric Films Fabricated by In Situ Grafting a Eu³⁺ Complex

Silicon-based solar cells (Si-sc), which are the main force of the photovoltaics, are facing challenges, including poor resistance to environmental factors such as ultraviolet radiation aging, water vapor permeation, fire risk, and response only in the visible light spectra and potential induced degradation effect. Aiming to solve these problems, the multifunctional polyolefin elastomer (POE) films were fabricated through in situ grafting of a highly efficient Eu3+ complex Eu(AA)(TPPO)2(TTA)2 (ETAT, where AA denotes acrylic acid, TPPO stands for triphenylphosphine oxide, and TTA represents trifluoromethylacetone) in this work. Such a design improved the compatibility between POE and ETAT, leading to the high transparency of POE/ETAT films with a transmittance of over 92%. Moreover, due to the enhanced entanglement of POE chains with the grafted 1.00 wt % ETAT, the water vapor permeability was decreased by 45% and the higher volume resistivity was obtained with the increase of 255%. The fire retardancy and the antiyellowing properties were also improved. Especially, the good luminescent down-shifting property of POE/1.00% ETAT films can endow Si-sc with the enhanced conversion efficiency of 1.64% and increased ΔJsc of 0.78 mA cm−2, compared with the untreated POE films. This study offers a facile and promising strategy for developing multifunctional encapsulation films for the photovoltaic industry.