The invention relates to a method for doping a semiconductor material with Cesium, wherein said semiconductor material is exposed to a cesium vapor. Said Cesium vapor is provided by Cesium sublimation from a Cesium alloy. There is also provided an organic light emitting diode comprising at least one layer of a Cesium doped organic semiconductor material, wherein said at least one layer of said Cesium doped organic semiconductor material is doped with Cesium provided by Cesium evaporation of Cesium from a Cesium alloy. The Cesium vapor is preferably provided by Cesium sublimation from a standard organic material deposition evaporator.