SnO2-NiO heterojunction based self-powered UV photodetectors

Thin film p-n heterojunction diodes using NiO and SnO 2 are fabricated, and the performances are studied. NiO was deposited using rf magnetron sputtering and SnO 2 using the electron beam evaporation technique. The diodes are fabricated in the configuration, FTO/SnO 2 /NiO/Au, with two different device areas; smaller with 0.35 mm circular diameter and larger with 2 × 2 mm square. The smaller device has a reverse leakage current of 20 µA at − 2 V, turn-on voltage of 1.2 V, and diode rectification ratio of 160, which are much higher than the reported SnO 2 /NiObased diodes. On the other hand, the larger area device exhibits a smaller rectification ratio of 4. UV photoelectron spectroscopy (UPS) analysis was carried out, and the work function of NiO was calculated as 5.31 eV. The deduced staggered band alignment of SnO 2 /NiO favors the effective separation of photogenerated charge carriers when illuminated with UV light. Subsequently, the diodes were tested for UV photodetection. Remarkably, the FTO/SnO 2 /NiO/Au diodes display self-powered UV photodiode characteristics using 365 nm light. Photoresponsivity of 3.3 mA/W, ON/OFF ratio of 4.16 × 10 4 , and detectivity of 7.4 × 10 10 Jones are obtained for the larger area device. At low incident light intensity, the larger area device exhibited a response time of 89 ms. • Rectifying thin film p-n type heterojunctions of SnO2/NiO are fabricated. • Device structure FTO/SnO2/NiO has a transparency of 48% at 550 nm. • Formation of type-ІІ band alignment at the p-n interface is confirmed using UPS measurement. • The devices functions as a self-powered UV photodetector, exhibiting high ON/OFF ratio and rise-decay times in milliseconds.