A comparison of the electrical characteristics of TiO₂/p-Si/Ag, GNR-TiO₂/p-Si/Ag and MWCNT-TiO₂/p-Si/Ag photodiodes

The TiO₂/p-Si/Ag, graphene nanoparticles doped (GNR) TiO₂/p-Si/Ag and multi-walled carbon nanotube (MWCNT) doped TiO₂/p-Si/Ag photodiodes were fabricated by electro-spinning technique at the same experimental conditions, and their structural, morphological and electrical properties were compared for photodiode applications. XRD measurements were confirmed undoped, GNR and MWCNT doped TiO₂ structures, and brookite phase of (121) preferred orientation TiO₂ has been observed from XRD patterns. SEM images of the heterojunctions showed that undoped and doped TiO₂ layer have homogenous surfaces. I–V measurements were performed for electrical characterization of the TiO₂/p-Si/Ag, GNR-TiO₂/p-Si/Ag and MWCNT-TiO₂/p-Si/Ag photodiodes under dark and light illumination conditions at room temperatures. The results imparted that all heterojunctions have good rectifying and photodiode properties. Some heterojunction parameters such as ideality factor, barrier height, series resistance were calculated and discussed in details according to thermionic emission theory, Cheung and Norde techniques. The determined ideality factor values are 8.55, 9.70 and 8.99, and barrier height values are 0.75 eV, 0.74 eV and 0.73 eV for the TiO₂/p-Si/Ag, GNR-TiO₂/p-Si/Ag and MWCNT-TiO₂/p-Si/Ag photodiodes, respectively. These heterojunctions can be considered and improved as photodiodes in industrial applications.