The recently introduced technique of near field scanning optical microscopy (NSOM) with an electrically biased NSOM probe is applied in this paper to the study of exciton/polaron interactions in single crystals of the mixed organic semiconductor, tetracene doped with pentacene. As in the case of the previously investigated conjugated polymers, the injection of hole polarons induces extreme fluorescence quenching for tetracene/pentacene. However, the spectral selectivity, dynamics, and other features of the tetracene/pentacene data suggest a different mechanism than conjugated polymer for hole polaron interactions. The tetracene/pentacene mechanism is dominated by hole trapping by pentacene.