Indium tin oxide is generally used as an anode material. It is transparent in visible light and has a high work function. Metals such as aluminum and calcium are often used as cathodes because they have low work function. When voltage is applied through the OLED, it is positively charged relative to the catheter, which provides electron flow through the cathode. In other words, the cathode emits electrons to the emitter layer and the anode receives these electrons from the conductive layer, so that the emitter layer becomes negative holes and the conductive layer becomes positive holes. Due to these charge interactions, the electric forces are correct. This emitter is close to the layer because organic semiconducting holes are much more mobile than electrons. This combination causes a reduction in the energy levels of the electrons, which is a consequence of a radiation spread having an apparent frequency of the region. This explains why this layer is called a spreader.