Zr-doped SnO2 thin films synthesized by spray pyrolysis technique for barrier layers in solar cells

In the present work, we investigated the effect of Zr doping (0-6 at%) on the structural, electrical, and optical properties of tin oxide (SnO2) thin films deposited onto glass substrates using a spray pyrolysis technique. The room-temperature X-ray diffraction pattern shows that all deposited films exhibit polycrystalline tetragonal structure. The pure SnO2 film is grown along a preferred (200) direction, whereas Zr-doped SnO2 (Zr:SnO2) films started growing along the (220) orientation along with a high intensity peak of (200). Scanning electron microscope (SEM) and atomic force microscope (AFM) images showed that the grains of the films are spherical in structure, and the grain size decreased with increasing of Zr concentration. The optical transmission spectra of deposited films as a function of wavelength confirm that the average optical transmittance is > 85% for Zr:SnO2 films. The value of the optical bandgap is significantly decreased from 3.94 to 3.68 eV with increasing Zr concentration. Furthermore, the electrical measurements found that the sheet resistance (R-sh) and resistivity (rho) values are decreased with increasing of Zr doping. The lowest values of R-sh = 6.82 Omega and rho = 0.4 x 10(-3) Omega cm are found in 6-at% Zr-doped SnO2 film. In addition, a good efficiency value of the figure of merit (phi = 3.35 x 10(-3) Omega(-1)) is observed in 6-at% Zr-doped SnO2 film. These outstanding properties of Zr-doped SnO2 films make them useful for several optoelectronic device applications.