We report the observation of photoluminescence quenching in thin films of poly(3-hexylthiophene) and Langmuir-Blodgett films of poly(3-hexylthiophene)/arachidic acid by the injection of positive charges in the polymer. Charge injection was made in a polymer field effect transistor, used in what we name the luministor mode. The quenching is discussed in terms of polarons/bipolarons acting as recombination centra for the excitons, suppressing the photoluminescence. The inverse phenomenon, luminescence enhancement by depletion of charges, has also been achieved.