Reduction of the firing voltage in plasma display panels calls for electrode coatings with a high secondary-electron yield. We have explored a range of materials that exhibit very low firing voltages, and a 50% reduction has been achieved relative to the best quality MgO. It is further shown that a high electron emission yield originates from both ion- and photon-induced processes, and is strongly influenced by the electronic structure of the material in terms of band gap and electron affinity.