Electrical Performance and Photoresponse of Thin Film Transistor Based on Hybrid Blend P3HT:Mg-Doped ZnO: Assessment of Gaussian DOS Distribution and Surface Potential Models

A composite of poly3-hexylthiophene (P3HT) and magnesium-doped zinc oxide (MZO1%) with 1 atom % of Mg in ZnO nanoparticles has been used to fabricate a light-sensitive phototransistor. The sol–gel process was employed for producing MZO1% nanoparticles. Mg has been incorporated into the ZnO lattice, as confirmed by the XRD patterns and TEM observations. The resulting nanoparticles are typically prismatic in form with diameters ranging from 50 to 57 nm. To investigate the concentration effect on optical properties, the P3HT:MZO1% blend thin films were developed in different amounts from 0 to 150 mg, and the band gap of the samples was calculated. Organic thin film transistors (OTFTs) based on P3HT:MZO1%, as an active layer deposited onto an n-doped silicon dioxide (SiO2) substrate by using the spin-coating technique, fabricated at a lower temperature, and it was characterized in ambient air. It revealed remarkable performances under light exposure. The photosensitivity of the device can be attributed to the accumulated electrons trapped by MZO1% nanoparticles in the channel. Finally, an analytical model for organic thin film transistors (OTFTs) that uses the variable range hopping (VRH) theory by writing a Matlab program to discuss the Gaussian DOS distribution and the surface potential of the P3HT:MZO1% blend-based OTFTs in the dark and under illumination for various MZO1% amounts of 50, 100, and 150 mg/mL based on Boltzmann and Fermi–Dirac statistics is presented. This model explains the influence of the MZO1% amount and illumination on the charge carrier density and the Gaussian distribution of occupied states (GDOS) effectively on the surface potential. In the dark, the MZO1% amount effect can remarkably enhance the surface potential and the Gaussian DOS distribution as well as reduce energetic disorder. However, under light illumination, we mainly notice a decrease in the interface trap density.