Upconversion white light devices: Ln(3+)-tridoped NaYF4 nanoparticles and PVP modified films

Upconversion (UC) white light hybrid thin films containing Ln(3+)-tridoped (Yb3+, Er3+ and Tm3+) NaYF4 nanoparticles and poly(vinyl pyrrolidone) (PVP, M(w) approximately 1300000) were prepared by a spin-coating method and characterized by X-ray diffraction (XRD), field emission scanning electron micrograph (FE-SEM) and Fourier transform infrared spectra (FT-IR). White light was generated by two different lanthanide ions, Er3+ (red and green) and Tm3+ (blue) under excitation by a 980-nm laser diode. Due to the modification of PVP to the UC populating processes, the color stability of the white light in the hybrid films was remarkably improved.