SOME ELECTRICAL AND PHOTOVOLTAIC PROPERTIES OF POLY-SI/SNO2 HETEROJUNCTION

Thin films of antimony-doped SnO2 deposited on polycrystalline silicon formed a heterojunction with SIS ("Semiconductor-Insulator-Semiconductor") structure, since an interfacial layer of SiOx between Si and SnO2 was always present. Thin films of SnO2 were formed by a new modification of the CVD (Chemical Vapour Deposition) method. The deposition parameters and the doping by antimony (Sb) were optimized in order to obtain SnO2 films of low sheet resistance, while maintaining high solar transmittance. DC current-voltage, (I-V) characteristics of the heterojunctions were measured in the dark at different temperatures and under sunlight, together with the output I-V curves. The experimental results indicate that multi-step tunnelling through the silicon barrier might be the predominant current transport mechanism in the dark, at least in the temperature range between 290 and 360 K. It is suggested that photovoltaic properties of these n-SnO2/n-Si (poly) heterojunctions could be improved by applying a metal grid front contact to SnO2 and by using thicker SnO2 films with lower sheet resistances. © 1990.