Fabrication and Characterization of SnO2/Si Heterojunction Solar Cells

Abstract

Transparent conducting SnO2 films (both undoped and antimony-doped) are deposited by oxidation of SnCl2 (SnCl2+SbCl3 in the case of doped films), at different deposition temperatures, oxygen (SnCl2 carrier gas) flow rates and nitrogen (SbCl3 carrier gas) flow rates. The structural, electrical and optical properties are studied and the deposition parameters are optimized for obtaining films with the lowest sheet resistance and highest transparency. Undoped films with the maximum figure-of-merit (transparency10/sheet resistance)=1.43×10-3 ohm-1 (sheet resistance = 420 ohm/square and per cent transparency=95) are obtained when deposited at 500°C with oxygen flow rate=l l.min-1. The figure-of-merit increases to 6.78×10-3 ohm-1 (sheet resistance =55 ohm/square and percent transparency=90.6) when antimony mole per cent in the film is 3. Solar cells are fabricated by depositing undoped and antimony doped SnO2 (ATO) films on n- and p- single-crystal silicon (1 ohm-cm) at the optimized set of deposition parameters. The open-circuit voltage, short-circuit current, fill factor and efficiency of the SnO2//n-Si cells are 0.52 V, 21 mA/cm2, 0.62 and 6.71 per cent respectively. These parameters for ATO/n-Si cell are 0.52 V, 24 mA/cm2, 0.68 and and 8.5 per cent and for ATO/p-Si cell are 0.22 V, 16 mA/cm2, 0.53 and 1.95 per cent. These experimentally-obtained results are explained theoretically.