Energy transfer mechanism of KAlF4:Dy3+, Eu3+ co-activated down-conversion phosphor as spectral converters: An approach towards improving photovoltaic efficiency by downshifting layer

Abstract

Rare earth activated fluoride phosphors have attention in recent years in the field of solid state lighting and solar cell efficiency enhancement. In the present study, RE (RE = Dy3+, Eu3+) activated/co-activated KAlF4 phosphor has been synthesized by low temperature wet chemical method. The structural feature of the samples was analyzed by X-ray Diffraction (XRD), which showed that the samples were crystallized in a well known structure. Photoluminescence (PL) measurement of KAlF4:Dy3+ phosphors we find that they can be efficiently excited at 351 nm and possess dominant emission bands centered at 482 nm (blue) and 572 nm (yellow). From Photoluminescence (PL) measurement of KAlF4:Eu3+ phosphors a strong orange emission at the peak wavelength of 594 nm and 616 nm were observed which could be attributed to the 5D0 → 7F1 and 5D0 → 7F2 transition in Eu3+ ions. On co-doping of rare earths in the host lattice, a strong blue and yellow emissions were observed together with the red emission. This co-doped phosphor is the coated on Si-solar cell by doctor blade method. Solar cell efficiency has been checked by I-V characteristics of the coated and blank cell. Theoretical quantum efficiency has been determined by Judd–Ofelt parameters for the proposed phosphor.