Impact of Ca2+, Ce3+ codoping on ZnSnO3-SnO2 heterostructure for dielectric, optoelectronic and solar cell applications

Abstract

We have successfully prepared a new mixed oxide system of Sn-rich ZTO (ZnSn2O5). The impact of coupling Ca2+ and Ce3+ inside the lattice of ZnSn2O5 on the dielectric, optical, and photoelectric conduction properties was investigated. In this regard, the co-precipitation technique was used to prepare three samples of ZTO, Ca-ZTO, and Ca/Ce-ZTO. The samples have been investigated by X-ray diffractometer (XRD), Fourier transform infrared (FTIR), field emission scanning electron microscope (FESEM), X-ray photoelectron spectrophotometer (XPS), and an energy dispersive X-ray spectrometer (EDS). The XRD pattern detected phases that highly interfere as a heterostructured compound. The pristine ZTO particles demonstrate a mixture of two morphologies, hexagonal and quasi-spherical shapes, with particle size distributions of 0.25–1.5 µm, resulting in significant porosity between these particles. Meanwhile, the particles of Ca/Ce-doped ZTO have a homogenous morphology as spherical shape and exhibit larger density, particle size distribution range of 1–2 µm. The dielectric constant as a function of frequency or wavelength is increased with the applied temperature (32 to 140 °C) for both pure and Ca/Ce-ZTO samples. Clearly, Ca/Ce-ZTO displays higher absorption in visible light and the estimated band gaps of ZTO, Ca-ZTO, and Ca/Ce-ZTO are equal to 1.58,1.56 and 1.48 eV, respectively. The pristine ZTO showed a stronger n-type effect than Ca and Ca/Ce-doped ZTO samples. The shift from n-type to being close to N-P junction by multiple doping induces the application of these heterostructured materials as buffering layers in energy conversion applications like thin film solar cells and light emitting diodes.