The authors have realized a light-emitting organic field-effect transistor. Excitons are generated at the interface between a n-type and a p-type organic semiconductor heterostructure inside the transistor channel. The dimensions and the position of the p-n heterostructure are defined by photolithography. The p-n heterostructure is at a distance of several microns from the metal electrodes. Therefore, the exciton and photon quenching in this device is reduced. Numerical simulations fit well with the experimental data and show that the light-emitting zone can move within the transistor channel. (c) 2006 American Institute of Physics.