Efficient near-infrared quantum splitting in YVO4:Ho3+ for photovoltaics

A sequential two-step near-infrared (NIR) quantum splitting (QS) has been demonstrated in a Ho3+-doped YVO4 phosphor, whereby one incident ultraviolet (UV)-to-visible photon, enabling Ho3+:F-S(4),S-5(2) excited, could be split efficiently into two NIR photons with emissions at 1015 and 1190 nm, respectively. The involved NIR-QS mechanism has been analyzed in terms of the static-dynamic photoemission, monitored excitation spectra and time-resolved emission spectra. Internal quantum yield is obtained up to 112% on the basis of experimental and theoretical calculation results. It is found that the broadband [VO4](3-) group as a sensitizer could efficiently transfer its energy to Ho3+ activator ions, thus dramatically enhancing the UV photo-response and the NIR luminescence intensity of the phosphor. Further development of this two-step two-photon NIR-QS phosphor may open up a new approach for enhancing the photo-response of photovoltaic cells, particular in the wavelength range of 250-560 nm. (C) 2012 Elsevier B.V. All rights reserved.