Preparation and application of the novel UV-curable polyurethane acrylate coatings with down-shifting luminescence

Commercial silicon-based solar cells usually worked at a narrow band of sunlight, so the response of silicon solar cells in the ultraviolet region is poor. To improve photovoltaic conversion efficiency, we developed novel UV-cured polyurethane acrylate composite coatings (PUA-Y) with highly efficient down-shifting luminescence properties. The PUA-Y coating consists of three key components. The first component is the synthetic vinyl end-capped polyurethane acrylate prepolymer (PUA-0), which uses a weather-resistant soft and hard segments. The second component is a UV absorber monomer RUVA-93 [2-(2-hydroxy-5-(2-(methylacryloyloxy) ethyl) phenyl)-2H-benzotriazole] that can copolymerize with PUA-0, and the third component is the synthetic europium complex Eu (LA)₃Phen as a luminescent downshift agent. A series of PUA-Y coatings were prepared by UV curing reaction using PUA-0, RUVA-93 and Eu (LA) 3 Phen with different composition ratios. The PUA-Y composite coated modified silicon solar cells were prepared by solution coating and UV curing. The coating system synergistically converted ultraviolet light into visible light through the ligand-to-metal charge transfer (LMCT) of Eu (LA)₃Phen and the excited-state intramolecular proton transfer (ESIPT) of RUVA-93. The composite fluorescence spectrum exhibited well matching with the absorption spectrum of the silicon solar cell. The structures and properties of PUA-Y coatings and its components were characterized by using FTIR, XRD, 1 HNMR, SEM, EDS, DMA, UV–visible and fluorescence spectrophotometry. The results showed that the transmittance of the PUA-Y2 coating can reach 89.0 % within the visible light range by optimizing the blend reaction system. The short circuit current value increased by 8.14 %–8.24 % for the silicon-based solar cell coated with the PUA-Y2 coating compared to no coating, and the UV absorption efficiency improved by approximately 50.0 %. Compared with uncoated silicon-based solar cells, the power conversion efficiencies (PCE) of silicon-based solar cells coated with PUA-Y2 increased from 4.711 % to 5.624 %. This work has brought new breakthroughs for the organic coatings can significantly improve the photovoltaic conversion efficiency of photovoltaic solar cells and the spectral response range of photovoltaic silicon-based panels.