Polymer nanocomposite sunlight spectrum down-converters made by open-air PLD

Abstract We report, for the first time to our knowledge, on the polymer nanocomposite sunlight spectrum down-converters made by the concurrent multi-beam multi-target pulsed laser deposition (CMBMT-PLD) of phosphor and polymer in ambient air. Phosphor PLD targets were made of down-converting rare-earth (RE)-doped fluorides NaYF₄:Yb³⁺,Er³⁺, and NaYF₄:Yb³⁺,Tm³⁺ with a Stokes shift of 620 nm (from 360 to 980 nm), minimizing the effect of re-absorption. The phosphors were synthesized by the wet method. Polymer target was made of poly (methyl methacrylate) known as PMMA. Target ablation was conducted with 1,064 nm beams from an Nd:YAG Q-switched laser. Beam intensity was 2.8 × 10¹⁶ W/cm² for both targets. The substrate was a microscope glass slide. Phosphor nanoparticles with a size ranging from 10 to 50 nm were evenly distributed in the polymer matrix during deposition. The nanoparticles retained the crystalline structure and the fluorescent properties of the phosphor target. There was no noticeable chemical decomposition of the deposited polymer. The products of laser-induced reaction of the polymer target with atmospheric gases did not reach the substrate during PLD. Post-heating of the substrate at ∼90°C led to fusion of separate polymer droplets into uniform coating. Quantum yield of the down-conversion polymer nanocomposite film was estimated to be not less than ∼5%. The proposed deposition method can find its application in making commercial-size down-converter coatings for photo-voltaic solar power applications.