Organic light emitting diode (OLED) light source includes a plurality of stacked organic light emitting diode units comprised of a removable topmost organic light emitting diode unit and one or more removable underlying organic light emitting diode units. A power source is in electrical communication with the anode and the cathode of the topmost organic light emitting diode unit, wherein the underlying organic light emitting diode units are free from contact with the power source. As such, each OLED is sequentially operated upon removal of the topmost OLED unit, thereby providing redundancy as well as extending the operating lifetime of the OLED light source. Also disclosed are processes for operating the OLED light source.