OBSERVATION OF NANOSPHERICAL n-SnO2/p-Si HETEROJUNCTION FABRICATED BY ULTRASONIC SPRAY PYROLYSIS TECHNIQUE

Thin film of tin oxide (SnO2) was prepared on p-type polished silicon wafer by ultrasonic spray pyrolysis technique using SnCl4 precursor solution to fabricate nanospherical n-SnO2/p-Si heterojunction photoelectric device. Deposition of film was achieved at 400°C substrate temperature. The self-made ultrasonic spray pyrolysis system is very cheap and convenient. The microstructural, optical and electrical properties of the SnO2 film were characterized by XRD, SEM, XPS, UV-VIS spectrophotometer, four point probe and Hall effect measurement, respectively. The SnO2 film has the nanospherical particles. The electrical properties of heterojunction were investigated by I–V measurement, which reveals that the heterojunction shows strong rectifying behavior under a dark condition. The ideality factor and the saturation current density of this diode are 4.27 and 2.52 × 10-6 A/cm2, respectively. And the values of IF/IR (IF and IR stand for forward and reverse current, respectively) at 5 V is found to be as high as 248. The SnO2/p-Si heterojunction device exhibits obvious photovoltaic effect. Under an AM1.5 illumination condition, the open-circuit voltage (Voc), short-circuit current density (JSC), fill factor (FF) of the device are 150 mV, 3.9 × 10-3 mA/cm2 and 20.58%, respectively. High photocurrent is obtained under a reverse bias when the crystalline quality of SnO2 film is good enough to transmit the light into p-Si. Under 6.3 mW/cm2 illumination, when the reverse bias is -5 V, the photocurrent gain is as high as 86.