Comparative Analysis of Compact Modeled of Low-Voltage OTFTs on Flexible and Silicon Substrates for the Implementation of Logic Circuits

This article discusses the compact modeling of organic thin-film transistors (OTFTs) fabricated on both flexible and silicon substrates. These compact models are used to implement inverters, 2-input NAND gate, and half-adder circuits. For the compact modeling and circuit design, Silvaco TechModeler and Silvaco Gateway tools are utilized. Both the flexible and silicon substrate OTFTs operate at −2 V, with saturated currents of −2 and $- 3.9~\mu $ A, respectively. Comparative analysis using dc and transient behavior reveals that the OTFT on the flexible substrate has a delay of 3.7 ns and a gain of 4.7, while the OTFT on the silicon substrate has a delay of 5.5 ns and a gain of 3.2. The OTFT on the flexible substrate is approximately 49% faster and exhibits a gain 1.47 times higher than the OTFT on the silicon substrate. Furthermore, the OTFT on the flexible substrate successfully realizes half-adder outputs for all four input cases (00, 01, 10, and 11), whereas the OTFT on the silicon substrate fails to do so for all cases. These results demonstrate that the OTFT on the flexible substrate significantly outperforms the OTFT on the silicon substrate in terms of delay, gain, and output consistency for the given inputs. In the future, the OTFT on the flexible substrate’s quick response, high gain, and reliable performance in NAND and half-adder circuits could offer advantages in the development of complex memory circuits, analog circuits, and other applications.