Down-Conversion Polymer Composite Coatings with Multipeak Absorption and Emission

Jun Fang,Chunhua Lu,Cheng Zhu,Liang Fang,Yaru Ni,Wenying Zhou,Wenting Liu

doi:10.3390/coatings11030282

Jun Fang, Chunhua Lu + Show 5 more

Open Access

https://doi.org/10.3390/coatings11030282

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Abstract

Spectral adjustment is an effective method to increase light conversion efficiency of solar cells and to promote the growth of plants. Down-converter (DC) materials are considered to be one of the most effective methods of spectral modification. The focus of this work was to expand the spectral response range of down-conversion layers to achieve multipeak absorption and emission. Sr2CaMoO6:Sm,Na and YVO4:Bi,Eu, which have different excitation peaks in the UV-blue region and varied emission peaks in visible light regions, were prepared in this work. Sr2CaMoO6:Sm,Na can effectively produce red light at 648 nm upon excitation at 408 nm, while YVO4:Bi,Eu can produce red light at 618 nm upon excitation at 365 nm. Polymeric luminescent coatings with one single kind of phosphor were prepared separately before the two phosphors were mixed together in uniform polymer coatings. The two phosphors were also assembled in bilayer coatings with different concentrations. The results showed that high transmittances over 90% were achieved for the two composite coatings with the thickness of 20 and 30 μm. The increase in particle loadings from 1‰ to 4‰ slightly decreased coating transmittance but increased luminescence intensity. The increase in the ratio of Sr2CaMoO6:Sm,Na and YVO4:Bi,Eu from 5/1 to 10/1 resulted in high transmittance of the DC coatings, independent of total filler loadings (3‰ and 4‰) and coating thickness. The relative intensities of emission peaks can be adjusted conveniently by changing filler ratios. In addition, the transmittance and luminescent intensities of the coatings where the two phosphors were assembled in two layers were close to the uniform coatings, suggesting the negligible effect of UV light irradiation order. This work proved that the prepared coatings presented multipeak absorption and emission upon UV light excitation. These coatings can be expected to be applied in fields such as solar cells and agriculture greenhouses.

Highlights

We prepared Sr2 CaMoO6 :Sm,Na and YVO4 :Bi,Eu that have different excitation peaks in UV-blue regions and various emission peaks in visible light regions before they were used together as phosphors in transparent luminescent polymer coatings to broaden the absorption of incident light and achieve an excellent emission spectrum
The calculation ofand the electronic structures of YVO4 :Bi and Sr2 CaMoO6 :Sm,Na was a: Bi means that vanadate and molybdate phosphors were mixed separately in bilayered polymer performed with the density functional theory (DFT) American using the CASTEP
The partial density of states (PDOS) of YVO :Bi is illustrated in Figure 4 to explain

Summary

Introduction

When rare-earth ion concentration in inorganic phosphors is higher than a critical valve, a quenching effect occurs and reduces the luminescent ability. Charge defects often occur when trivalent rare earth ions are doped into the lattice to replace divalent metal ions. The excitation range can be further adjusted to blue light band via the addition of Sm3+ [44] Vanadate phosphors are another functional inorganic material. We prepared Sr2 CaMoO6 :Sm,Na and YVO4 :Bi,Eu that have different excitation peaks in UV-blue regions and various emission peaks in visible light regions before they were used together as phosphors in transparent luminescent polymer coatings to broaden the absorption of incident light and achieve an excellent emission spectrum.

Experimental

Effect of Doping of 6Sm phosphor samples of Amounts

Band Structure and Density of States

Influence of Particle Size

Preparations and Properties of Luminescent

Conclusions