Preparation Of Europium Complex/EAV Composite Film And Its Application In Crystalline Silicon Solar Cells

The luminescence of rare earth organic complex has the advantage of narrow emission spectrum,large Stokes shift and high fluorescent efficiency.In particular,Eu3+ complex which can absorb the ultraviolet and emit visible light at about 612 nm,may be introduced into ethylene-vinyl acetate（EVA）film by doping method or chemical bonding method.The luminescent down-shifting（LDS）film obtained can be used in crystalline silicon solar cell as a composite of encapsulating layer.LDS film absorbs the ultraviolet to prevent premature aging of photovoltaic modules and improves the spectral response of silicon photovoltaic modules in the ultraviolet region.However,optical losses accompanying in the LDS film will cause the decrease of visible light transmittance,which are not conducive to the improvement of the conversion efficiency.Therefore,EVA composite films used in silicon solar cell must possess the high visible light transmittance and strong fluorescence.In this work,several EVA composite films containing Eulu complex were prepared.UV-Vis light transmission and fluorescence intensities of EVA composite films were measured,and the surface morphology of the films was characterized.Each film was coated on the surface of a same polycrystalline silicon solar cell,and Ⅰ-Ⅴ characteristic of the solar cell was tested.The effects of visible light transmittance and fluorescence intensity of EVA composite film on the conversion efficiency were investigated.（1）The thermoplastic EVA film was prepared by casting method,and the key technological conditions such as the solvent selection,film-forming temperature and film-forming time were determined.The crosslinked EVA film was prepared by cross-linking of the thermoplastic film,and the key technological conditions such as curing temperature,curing time and the content of initiator were determined.Thus the obtained EVA film is flat,uniform and transparent.Transmittance of EVA film and Ⅰ-Ⅴ characteristic of the crystalline silicon solar cell coated with EVA flim were tested.The results show that the influence of visible light transmittance of EVA film on the conversion efficiency is direct and profound.（2）Two typical β-diketone Eu3+ complexes,Eu（DBM）3Phen（EuDP）and Eu（TTA）3Phen（EuTP）,were synthesized.EVA composite films doped with EuDP or EuTP were prepared by casting method,and UV-Vis light transmission and fluorescence properties of EVA composite films were characterized.The results show visible light transmittance of EuDP/EVA film is greater than that of EuTP/EVA film and the fluorescence intensity of EuTP/EVA film is stronger.SEM images of EVA composite films indicate that the compatibility of EuDP with EVA is better than that of EuTP with EVA.The different composite films were respectively coated on the surface of silicon solar cell,and then Ⅰ-Ⅴcharacteristics of that were measured.The results show that the conversion efficiency of the solar cell coated with EuDP/EVA film is higher than that of the solar cell coated with EuTP/EVA film.（3）By the introduction of 1-tridecanecarboxylic acid（TA）,quaternary complex Eu（DBM）2Phen（TA）（EuDPT）was synthesized.FT-IR,1H NMR,XRD and elementary analysis were used to characterize the complex.XRD analyses of the complexes shows that EuDPT inclines to amorphization compared with EuDP.The EuDPT/EVA composite film doped with EuDPT was prepared by casting method,and UV-Vis light transmission and fluorescence properties of the composite films were characterized.Compared with EuDP/EVA film,visible light transmittance of EuDPT/EVA film is improved obviously and the fluorescence intensity of EuDPT/EVA film decreases slightly.The surface microstructure of EVA composite film was characterized by SEM and AFM.The results show that the surface micromorphology of EuDPT/EVA film is like scaly shape and EuDPT particles are homogeneously dispersed in EVA film,which means compatibility of EuDPT with EVA is better than that of EuDP with EVA.The composite films were respectively coated on the surface of silicon solar cell,and then Ⅰ-Ⅴ characteristics of that were measured.The results show that the conversion efficiency of the solar cell coated with EuDPT/EVA film is higher than that of the solar cell coated with EuDP/EVA film.（4）Complex EuDPT and nano-SiO₂ modified by KH570 were co-doped into EVA film by casting method.And UV-Vis light transmission and fluorescence properties of EVA composite films were characterized.It is found that the fluorescence intensity of EVA composite film is enhanced and visible light transmittance of EVA composite film decreases slightly when the modified SiO₂ content is within 4%.The surface microstructure of EVA composite film was characterized by SEM and AFM.And many fold shape protrusions which are uniformly dispersing on the surface can be observed.So the fluorescence enhancement of EVA composite film is probably because EuDPT particles are enwrapped by the modified SiO₂ aggregations and the rigidity of the complex in structure is strengthened.The composite films were respectively coated on the surface of silicon solar cell,and then Ⅰ-Ⅴ characteristics of that were measured.The results show that the conversion efficiency of the solar cell coated with KH570-SiO₂/EuDPT/EVA film is higher than that of the solar cell coated with pure EVA film and has an increase of 0.14%.（5）By the introduction of acrylic acid（AA）,polymerizable complex Eu（DBM）2Phen（AA）（EuDPA）was synthesized.Bonding type EuDPA-EVA film was prepared by crosslinking EuDPA onto EVA.The experimental results show that about 20%of EuDPA molecules have taken part in the cross-linking reaction.And UV-Vis light transmission and fluorescence properties of EVA composite films were characterized.Compared with crosslinked EuDP/EVA film,visible light transmittance of EuDPA-EVA film is improved and the fluorescence intensity of EuDPA-EVA film decreases slightly.SEM images of EVA composite films indicate that the crosslinking between EuDPA and EVA can help to improve the compatibility of complex with EVA.The composite films were respectively coated on the surface of silicon solar cell,and then Ⅰ-Ⅴ characteristics of that were measured.The results show that the conversion efficiency of the solar cell coated with EuDPA-EVA film is higher than that of the solar cell coated with crosslinked EuDP/EVA film.