Core-shell nanophosphor with enhanced NIR-visible upconversion as spectrum modifier for enhancement of solar cell efficiency

A distinct enhancement of upconversion luminescence from core to core/shell (C/S) structure under low flux near infrared (NIR) excitation at 976 nm has been achieved in lanthanide (Er3+, Yb3+)-doped NaYF4 core with undoped NaYF4 shell nanoparticles (NP). A green chemistry approach has been taken to synthesize monodisperse monophasic C/S NP with the core (similar to 20 nm) and shell (similar to 5 nm) crystallizing into cubic phase. Hydrophobic C/S NP have been further made hydrophilic by coating a transparent SHMP layer without affecting luminescence. C/S (NaYF4: Er, Yb/NaYF4) NP integrated dye-sensitized solar cell indicated 11.9% enhancement in overall conversion efficiency under AM 1.5 conditions, due to NIR-visible spectrum modification by fluorescent NPs. The results indicate great potential of such upconverting C/S nanophosphor in solar cell applications.