Organic light-emitting transistors based on bilayered structures (see figure) exhibit balanced ambipolar transport and mobility values as large as 3 x 10(-2) cm(2) V-1 s(-1). The best performances are realized by sequentially depositing alpha,omega-dihexyl-quaterthiophene (DH4T) as p-type and N,N'-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13) as n-type materials. Laser-scanning confocal microscopy allows selective imaging of the layers.