Gd Doping-Induced Luminescence Red-Shift in the CaZrO3 Perovskite for Optoelectronics

Herein, we present results on the structural and optical properties of an undoped and a series of Gd-doped perovskites, CaZrO3, for a possible application in optoelectronics. We prepared different samples using the solid-state synthesis method. The powder X-ray diffraction pattern confirmed the formation of the host lattice and also suggested that the Gd ions replaced Ca ions in the host lattice. The UV–vis reflectance spectra suggested that the host band gap was 4.96 eV at room temperature. A shift in the photoluminescence emission was observed from 370 nm (emission for an undoped sample) to 465 nm (emission for a Gd-doped sample). The red shift has been assigned to the presence of defect distribution close to the conduction band in the host lattice and also to the internal energy-transfer process between Gd and defect levels. The same was confirmed by time-correlated photon counting decay measurements. The sample with a high Gd concentration (Ca0.96Gd0.04ZrO3) gives photoluminescence emission with the highest relative intensity, with approximately a three-fold intensity increase as compared to an undoped sample. We understand the mechanism of charge recombination via a vacuum-referred binding energy diagram to determine the energy transfer process responsible for an increase in emission intensity and concentration quenching for samples containing a higher concentration of doped Gd ions. The decay time in ns-regime and emission between 350 and 650 nm makes the present host–dopant combination a promising option for optoelectronics.