Characterization of antimony-doped tin oxide films for solar cell applications

Abstract

Transparent conducting undoped tin oxide (SnO 2) and antimony-doped tin oxide (ATO) films were deposited onto Pyrex glass and single-crystal silicon substrates using an inexpensive chemical vapour deposition system. SnCl 2 and SbCl 3 were used as the source reagents with oxygen and nitrogen respectively as the carrier gases. The deposition conditions were as follows: temperature, 350–500 °C; oxygen flow rate, 0.8–3.25 1 min -1; nitrogen flow rate, 0–0.1 1 min -1; deposition time, 5–20 min. The antimony concentration in the film and its physical properties were the same on both substrates. A figure of merit (Tr 10/ R sh where Tr is the transmission at a particular wavelength and R sh is the sheet resistance) was used to compare the performance of these films. The maximum figure of merit for SnO 2 films (1.43 × 10 -3 Ω -1 ( Tr = 95% and R sh = 420 Ω/□)) was obtained when they were deposited at 500 °C with oxygen at a flow rate of 1 1 min -1. The sheet resistance of antimony-doped films is a minimum at 3 mol.% Sb and the transmission decreases as the antimony concentration increases. The maximum figure of merit obtained for ATO films was 6.78 × 10 -3 Ω -1 ( Tr = 90.6% and R sh = 55 Ω/□) for an antimony content of 3 mol.% and a nitrogen flow rate of 0.07 1 min -1. These results are explained theoretically and are compared with those reported by other workers.