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

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.