Recent experiments have demonstrated ambipolar channel conduction and light emission in conjugated polymer field-effect transistors (FETs). Electrons and holes are injected from metal source and drain contacts with different work functions, propagate through the FET channel, and recombine emitting light. The position of maximum light emission is varied by changing the voltages applied to the transistor terminals. Here, we present an analytic device model for ambipolar organic field-effect transistors, based on the gradual channel approximation. Trapping of the injected carriers is found to be important. The model results are in good agreement with the experimental observations.
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The authors thank A. J. Heeger for useful suggestions and discussions. The work at Los Alamos National Laboratory was supported by DOE Office of Basic Energy Sciences Work Proposal No. 08SCPE973.