Examination of electrical properties of new-type composite-based al/p-si/nio:tio2/al photodiodes

In this master thesis, we present the optoelectronic characterization of thin-film photodiodes fabricated by a sol–gel route from pure NiO, pure TiO2, and NiO–TiO2 composites in varying ratios. Devices were deposited onto Al/p-Si/Al substrates, and their current–voltage (I–V) responses were measured under dark conditions and controlled illumination. Key performance metrics such as the photoresponse (Iph) and responsivity (PR) were evaluated to assess their light-sensing capabilities. Under reverse bias, all photodiode structures exhibited a clear generation of photocarriers when illuminated. Notably, the 1:1 TiO2:NiO composite device produced approximately 3500A of photocurrent at an illumination intensity of 100 mWcm−2. By contrast, the pure NiO photodiode demonstrated a responsivity of 2.5×10−2 AW−1 even at low light levels, underscoring its superior sensitivity. Pure TiO2 and TiO2-rich (3:1) composite devices, however, showed comparatively weaker photovoltaic responses. These findings highlight the critical influence of material composition, heterojunction quality, and film morphology on photodiode performance. In particular, the 1:1 TiO2:NiO composite effectively balances efficient charge separation with strong photoinduced current generation. Overall, sol–gel processed NiO/TiO2 photodiodes emerge as promising, low-cost, and scalable candidates for integration into next-generation optoelectronic sensing systems.