Drastically Improved Durability and Efficiency of Silicon Solar Cells Using Hyper-Stable Lanthanide Coordination Polymer Beads

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Remarkable improvements of environmental durability and energy conversion efficiency in silicon solar cells were achieved using ethylene vinyl acetate (EVA) protection film containing poly(methyl methacrylate) (PMMA) polymer beads (PB), which includes hyper-stable luminescent lanthanide coordination polymer [Eu(hfa)3(dpbp)]n (hfa: hexafluoroacetylacetonate, dpbp: 4,4′-bis(diphenylphosphoryl)biphenyl). The shape of PB including [Eu(hfa)3(dpbp)]n (PB-[Eu(hfa)3(dpbp)]n) was observed with SEM. Luminescence performance of EVA protection films including PB-[Eu(hfa)3(dpbp)]n or related lanthanide complexes (previously reported [Eu(hfa)3(dpbp)]n powder, Tb(hfa)3(TPPO)2, Eu(hfa)3(TPPO)2, and Yb(hfa)3(TPPO)2, TPPO: triphenylphosphine oxide) were characterized using emission spectroscopy, quantum yields, and lifetimes. Their durability were evaluated using photophysical measurements after degradation test (85 °C 85% RH). The durability of PB-[Eu(hfa)3(dpbp)]n in EVA film was estimated to be twenty-five years, which is much longer than those of previous lanthanide complexes. The temperature dependency of emission spectra of PB-[Eu(hfa)3(dpbp)]n confirmed that the luminescence properties are maintained even at high temperatures up to 120 °C. Increased value of the solar cell short-circuit current efficiency using EVA protection film containing PB-[Eu(hfa)3(dpbp)]n was found to be 1.1%, which is a drastic increase as a photovoltaic solar system. The EVA protection films with PB-[Eu(hfa)3(dpbp)]n are effective for enhancing the performance of silicon solar cells.