Influence of precursor concentration on the optoelectronic properties of spray deposited SnO2/Si heterojunction

Nanostructure SnO2/Si heterojunction were successfully prepared by spray pyrolysis technique at temperature 350 °C. Effect of precursor concentration on structural, optical and optoelectronic properties has been investigated. It is shown that the SnO2 thin films properties depend strongly on the precursor concentration. X-ray diffraction pattern show that the films are polycrystalline with (110) plane as preferred orientation for low solution concentration, higher concentration shift the preferred orientation gradually into (101) plane. SEM images revealed that films consist of nanograins that size remarkably decreases with increasing precursor concentration. The maximum optical transmittance of the films increases from 45% to 75% with increase in precursor concentration. The optical band gap of the films was increase from 3.23 eV to 3.46 eV. The current transport properties of the n-SnO2/p-Si heterojunctions are investigated by current-voltage measurements. The sample obtained from 0.1 M precursor exhibit higher electrical conductivity compared with the samples obtained from precursors with higher molar concentrations and the rectifying behavior was at 0.1 M and Ideality factor is 2.136. The linear behavior between 1/C2 and the applied voltage of SnO2/Si heterojunction in reverse bias indicates that the carrier concentration is homogenous in the depletion region of the SnO2 and the built-in potential decrease with increase the precursor concentration.