Thin film transistor structures have been used to study semiconducting poly(3-alkylthiopene) and quinquethiophene thin films. The holes in these materials are stored into self-localized polaronic states giving low values for the measured field-effect mobilities. The carrier mobilities in monolayers are lower than in thicker films. The extra holes injected into LB films in a transistor act as non-radiative recombination centers for photoexcited excitons. The transistor structure then acts as a luminescence quenching device. Some future prospects concerning LB electronics are presented.