Structural, surface, and upconversion luminescence properties of pulsed laser-deposited Y2O3:Ho3+,Yb3+ thin films

As a potential upconverting layer for solar cell applications, the effect of substrate temperature on the structural, surface, and upconversion (UC) properties of Y2O3:Ho3+,Yb3+ thin films was studied. On soda-lime glass substrates, pulsed laser deposition was used to generate the films. The structural and compositional analyses were performed using x-ray powder diffraction and x-ray photoelectron spectroscopy (XPS). The thicknesses of the prepared films were estimated using XPS depth profiles and cross-sectional scanning electron microscopy measurements. The UC and cathodoluminescence emissions revealed green, red, and infrared emission bands from Ho3+ ion transitions observed at 540, 550, 668, and 757 nm, corresponding to the 5F4 → 5I8, 5S2 → 5I8, 5F5 → 5I8, and 5S2 → 5I7 transitions under 980 nm excitation and high-energy electron excitation, respectively. The measurements of power dependency showed that a two-photon step method was used to proceed with the UC emission. Furthermore, the UC energy transfer process was thoroughly explored. The efficient UC emission results suggested that the Y2O3:Ho3+,Yb3+ films can be suitable for solar cell applications.