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.