Enhanced near-infrared downconversion luminescence in ZnxNb(1-x)O composite host co-doped Bi3+/Yb3+ phosphor for Si solar cell applications

The spectral modification is noticed through near Infrared (IR) downconversion (DC) in Yb3+, Bi3+ co-doped ZnxNb(1-x)O composite host. A high-intensity blue emission centered at 450 nm is observed upon UV excitation at 270 nm for the host ZnxNb(1-x)O at x = 0.5 (ZN). Doping with the optimized concentration at 4 mol% of Yb3+ with ZN (YZN) initiates an energy transfer from the niobate group to two neighboring Yb3+ ions in a cooperative energy transfer (CET) process. The resulting Yb3+ emission spectrum is around 1000 nm, which matches well with the spectral response of Si solar cells. Introducing 1 mol% of trivalent Bi3+ ions as an additional sensitizer to YZN (BZN), the excitation wavelength is further extended from UV at 270 nm to visible at 450 nm region. As an effect of this, UV excitations at 270 nm, 330 nm, and visible excitation at 450 nm in BZN enhance the luminescence in the near IR region. The DC process observed in BZN is due to the CET process from both the niobate group and Bi3+ ions to Yb3+ ions. Solar panel coated with BZN shows an increase in conversion efficiency which in turn indicates that the synthesized phosphor is a promising material for increasing Si solar cell efficiency.