The Simulation Of Organic Field Effect Transistor Characteristic Based On The Finite Element Method

Organic field-effect transistors(OFETs)have received wide attention for their several advantages such as low cost,light weight,compatible with flexible substrates,suitable for large area low temperature fabrication,and so on.They have been applied in RF cards,sensors,optical probe,electronic tags,signal storage and driving circuit of organic flat panel display.Therefore,it is important to study OFETs.At present,the researches on OFETs mainly focus on experiments and theories,the theoreilcal progress is slower than the experimental progress,which is a problem urgent to solve.By using computer simulation method to study the theoretical of OFETs,the physical and electrical characteristics of OFETs can be simulated and analyzed.It is not only save the cost but also improve the efficiency.Around this theme,the distribution of potential and carrier density under the various source drain voltage of OFET with bottom-gate top-contact geometry was simulated by using the multi-physical field software COMSOL on the basis of the finite element method.The specific contents are as follows:(1)The potential distribution of OFET was studied.At first,we add electrostatic module to multi physics field and build the physical model,then set solution domain and boundary conditions according to the Poisson equation.Finally,we adopt the mesh refinement to obtain the numerical solution of the Poisson equation.The results show that the potential has gradually change from source electrode to gate electrode in the vertical direction with the increase of source drain voltage on the gate voltage Vg=-10 V and source drain voltage Vds in the range from 0V to-10 V,while the potential in the horizontal direction is even more obvious,showing an evident gradient change from high to low.(2)The carrier concentration distribution of OFET was studied.Firstly,we add convection and diffusion module to multi physics field and build the physical model,then set solution domain and boundary conditions according to the current continuity equation.Finally,we obtain the numerical solution of the current continuity equation by the mesh refinement method.The results show that the distribution of the carrier density becomes gradually reduced from source electrode to drain electrode in the channel and an evident reduction was observed near the drain with the increase of source drain voltage.(3)We simulated the potential distribution and the carrier concentration distribution of the OFET with the different insulating layer and insulating layer thickness.Comparing the simulation results to the experimental results of the OFET with the insulating layer of PMMA and PI and the thickness of PMMA of 260 nm 310 nm,390 nm and 410 nm.It was found that the ? is reduced and the source drain current Ids is increased with the permittivity ? increases,but the carrier concentration p and the source drain current Ids all decreases when the the thickness d is enlarged.The simulation results are consistent with the experimental ones,which confirms the rationality of the simulation.