Fabrication and characterization of polyaniline/porous silicon heterojunction

Heterojunction between polyaniline (PANI) and porous silicon (PS) was fabricated by making a layer of PANI on PS, using spin coating method. PS was fabricated by electrochemical etching process. PS was characterized by photoluminescence (PL), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) while the PANI was characterized by FTIR and absorption (UV-VIS) spectroscopy. Current-voltage and capacitance-voltage measurements were done to determine the electrical properties of the heterojunction structure. The ideality factor of the heterojunction was found to be 4.2, which was considered high due to large defect density at the interface. Built-in potential was measured by both I-V and C-V and was found to be Φb(I-V) = 0.41 V and Φb(C-V) = 0.28 V respectively. The discrepancy in the values of the built-in potential was discussed. Band discontinuity in conduction band and valence band were found to be 0.65 and 1.27 eV respectively. Solar response of the heterojunction was also observed at AM (air mass) 1.0 and it showed a promising behavior as a photovoltaic device.