Modeling of Electrical Characteristics of Thin-Film Transistors Based P3HT:ZnO Blend: Channel Length Layer Effect

In the current study, p-type thin-film transistors (TFT) based on poly(3-hexylthiophene) (P3HT) and zinc oxide (ZnO) nanoparticles with channel length L = 2.5 m, 5 m, 10 m, and 20 m were developed and characterized using solution-processed P3HT. Without any surface preparation, spin coating was used to create P3HT:ZnO thin films as an active layer on a -SiO2/ Si substrate. In order to better understand the relationship between the electrical performance and the channel length, we investigated the effect of varied channel length on the electrical characteristics of these transistors at room temperature in the saturation regime. The fabricated devices showed significant variation in electrical parameters as a function of channel length, including the threshold voltage (V-th), density of trapped charges (N-trap), subthreshold slope (SS), density of the interface trap (D-it), field-effect saturation mobility (mu(sat)), and current ratio (I-on/I-off). This paper discusses the Gaussian DOS distribution (GDOS) of the P3HT:ZnO TFTs for various channel layer lengths using an analytical model for organic TFTs (OTFTs) based on the variable-range hopping (VRH) theory. This model appropriately describes the GDOS. Finally, we used a generic drift model to reproduce the output characteristics of TFT-P3HT. The derived theoretical results exhibit excellent agreement with the experimental data. The value of the mobility in the P3HT transistors is lower than that of the P3HT:ZnO blend, confirming the advantage of introducing the ZnO nanoparticles.