Light-emitting devices using a polymer/clay nanocomposite with good gas-barrier properties were fabricated by blending poly[2-methoxy-5-(2 ' -ethyl-hexyloxy)-1,4-phenylenevinylene] with organo-clay. This two-dimensional lamellar type nanocomposite structure efficiently confines not only electronic charge carriers but also ionic ones. Transient electroluminescent (EL) measurements of the light-emitting devices driven by pulsed voltage revealed that the electronic charge carrier mobility of the nanocomposite device was reduced, which suggests that the electronic char-e is blocked to improve the bipolar recombination rates. From transient current and EL behavior of the devices driven by applying a steady-state electric field, we determined the ionic charge mobilities of the devices and confirmed that the clay also hindered the movement of ionic charges within the composite.