Certain example embodiments relate to organic light emitting diode (OLED)/polymer light emitting diode (PLED) devices, and/or methods of making the same. A first transparent conductive coating (TCC) layer is disposed, directly or indirectly, on a glass substrate. An outermost major surface of the TCC layer is planarized by exposing the outermost major surface thereof to an ion beam. Following said planarizing, the first TCC layer has an arithmetic mean value RMS roughness (Ra) of less than 1.5 nm. A hole transporting layer (HTL) and an electron transporting and emitting layer (ETL) are disposed, directly or indirectly, on the planarized outermost major surface of the first TCC layer. A second TCC layer is disposed, directly or indirectly, on the HTL and the ETL. One or both TCC layers may include ITO. The substrate and/or an optional optical out-coupling layer stack system may be planarized using an ion beam.