Physical properties of electrically conductive Sb-doped SnO2 transparent electrodes by thermal annealing dependent structural changes for photovoltaic applications

We have investigated the optical and electrical characteristics of antimony (Sb)-doped tin oxide (SnO2) films with modified structures by thermal annealing as a transparent conductive electrode. The structural properties were analyzed from the relative void % by spectroscopic ellipsometry as well as the scanning electron microscopy images and X-ray diffraction patterns. As the annealing temperature was raised, Sb-doped SnO2 films exhibited a slightly enhanced crystallinity with the increase of the grain size from 17.1 nm at 500 degrees C to 34.3 nm at 700 degrees C. Furthermore, the refractive index and extinction coefficient gradually decreased due to the increase in the relative void % within the film during the annealing. The resistivity decreased to 8.2 x 10(-3) Omega cm at 500 degrees C, but it increased rapidly at 700 degrees C. After thermal annealing, the optical transmittance was significantly increased. For photovoltaic applications, the photonic flux density and the figure of merit over the entire solar spectrum were obtained, indicating the highest values of 5.4 x 10(14) cm(-2) s(-1) nm(-1) at 1.85 eV after annealing at 700 degrees C and 340.1 mu A cm(-2) Omega(-1) at 500 degrees C, respectively. (C) 2011 Elsevier B.V. All rights reserved.