General properties of SnO2-GaAs and SnO2-Ge heterojunction photovoltaic cells

SnO2-Ge and SnO2-GaAs heterojunction formed by chemical vapor deposition have been investigated. The results show that (n-n) SnO2-GaAs, (n-p) SnO2-GaAs, and (n-n) SnO2-Ge heterojunctions give a photovoltaic effect, while (n-p) SnO2-Ge yields an ohmic contact. The measured short-circuit currents, arising mainly from semiconductor side, are comparable with those for "AMOS" and homojunction solar cells. The open-circuit voltage and fill factor and considerably less. The polarity observed in Vocand Iscis consistent with the band bending of a simple SnO2-semiconductor heterojunction energy-band diagram neglecting interface states. The ohmic behavior for (n-p) SnO2-Ge is attributed to the accumulation layer existing between SnO2conduction band and Ge valence band at the interface.