New insight into rare-earth doped gadolinium molybdate nanophosphor assisted broad spectral converters from UV to NIR for silicon solar cells

Abstract

We have successfully synthesized rare-earth doped gadolinium molybdate Gd₂(MoO₄)₃:Re³⁺ (Re³⁺ = Eu³⁺, Tb³⁺, Tm³⁺ and Er³⁺/Yb³⁺) nanophosphors for solar cell application as a broad spectral converter from the ultraviolet (UV) to the near infrared (NIR) regions in a single host lattice using a facile solid state reaction method. The gross structure, surface morphology and microstructure of these nanophosphors have been investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission/high-resolution transmission electron microscopy (TEM/HRTEM) techniques , respectively. Photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectroscopic methods have been used to explore the striking luminescence properties of the synthesized nanophosphors. The Gd₂(MoO₄)₃:Eu³⁺ nanophosphor exhibits a hypersensitive red emission (616 nm) at an excitation wavelength in the range of 250–475 nm corresponding to a ⁵D₀–⁷F₂ transition. The Gd₂(MoO₄)₃:Tb³⁺ and Gd₂(MoO₄)₃:Tm³⁺ nanophosphors demonstrate a strong green emission at 541 nm and a deep blue emission at 453 nm upon an excitation wavelength of 378 nm and 266 nm, respectively. Moreover, the upconversion characteristic of the Gd₂(MoO₄)₃:Er³⁺/Yb³⁺ nanophosphor exhibits strong green emission at 545 nm and red emission at 657 nm corresponding to ⁴S_3/2–⁴I_15/2 and ⁴F_9/2–⁴I_15/2 transitions respectively. Furthermore, the Gd₂(MoO₄)₃:Er³⁺/Yb³⁺ upconversion nanophosphor emits in the NIR spectrum region at 994 nm upon a 980 nm excitation wavelength. Hence, the obtained PL emission results with a lifetime in milliseconds reveal that these nanophosphors could be futuristic promising broad spectral converter phosphors which may possibly integrate with the next-generation Si-solar cell to enhance the efficiency of the cell.