Thin film transistors are provided that include a metal oxide active layer with source and drain regions having a reduced resistivity relative to the metal oxide based on doping of the source and drain regions at room temperature. In an aspect, a transistor structure is provided, that includes a substrate, and source and drain regions within a doped active layer having resulted from doping of an active layer comprising metal-oxide and formed on the substrate, wherein the doped active layer was doped at room temperature and without thermal annealing, thereby resulting in a reduction of a resistivity of the source and drain regions of the doped active layer relative to the active layer prior to the doping. In an aspect, the source and drain regions have a resistivity of about 10.0 mΩ·cm after being doped with stable ions and without subsequent activation of the ions via annealing.