NaYF4 : Yb,Er—an efficient upconversion phosphor

Abstract

Studies of the infrared-pumped visible luminescence of NaYF4 : Yb, Er show it to have at least twice the visible output of YF3 : Yb, Er when pumped with a narrow-band excitation source at the optimum frequency. It is also free from saturation effects until very intense excitation levels are reached. The mechanism for red upconversion appears to change with increasing excitation from a two-step process to one involving a significant amount of three-step upconversion, which change is accompanied by an increase in the response time for visible emissions.

Synthesis and Upconversion Luminescence of Hexagonal‐Phase NaYF4:Yb, Er3+ Phosphors of Controlled Size and Morphology

“…[10] Its emission is at least two-times greater than that of YF 3 :Yb, Er 3+ at optimum excitation. [11] When doped with Yb, Er…”

Photochemical upconversion: present status and prospects for its application to solar energy conversion

“…The highest upconversion efficiencies realized to date for inorganic materials have been observed for solid matrices doped with lanthanoid ions, such as Gd 3+ , Dy 3+ , Er 3+ , Yb 3+ or Tm 3+ . One of the most efficient UC phosphors to date is NaYF 4 , doped with Er 3+ or co-doped with Yb 3+ and Er 3+ , which was introduced in 1972 by Menyuk et al 74 Comprehensive reviews of ETU by f -shell ions in solid bulk matrices and nanoparticles include the works by Auzel 11 and Haase et al 75 The first realization of an upconversion-assisted solar cell was based on Yb 3+ and Er 3+ ions in a vitroceramic host, placed behind a GaAs solar cell. 76 The first application of the same system to c-Si solar cells was demonstrated in 2005 by Shalav et al, 13,77 and current lanthanoid-based upconversion efforts are mainly focused around crystalline silicon, 14,[78][79][80] due to the energetically favorable absorption of Er 3+ around 1523 nm, below the c-Si band edge in energy and within a local maximum of the solar spectral irradiance.…”

Upconversion-pumped luminescence efficiency of rare-earth-doped hosts sensitized with trivalent ytterbium

“…depended on the composition, with red being emphasized at higher Yb doping levels, The optimal concentrations of Yb and Er for producing green upconversion appeared to be 18.0 and 2.0 mol%, respectively. Most of the phosphors obtained from Sarnoff have been previously reported in the literature, including NaYF4:Yb,Er [6,8], Y202S:Yb,Er [9], Y203:Yb,Er [10], and Y2~S:Yb,Tm [9]. These materials are only available as powders, and cannot be readily grown as single crystals (in contrast to the Na2Y3F1I material).…”