A major global issue that the world is facing today is the upcoming depletion of fossil fuels and the energy crisis. In 1998, the global annual energy consumption was 12. 7 TW; of which 80% was generated from fossil fuels. This also translates into huge annual emissions of CO that leads to massive environmental problems, 2 particularly the global warming, which could be disastrous. Future global annual energy needs are also estimated to rise dramatically. A major challenge confronting the world is to ?nd an additional 14–20 TW by 2050 when our energy reserves based on fossil fuels are vanishing. The massive demand for energy would require materials and/or processes that would help to provide new sources of clean ren- able energy or to develop processes that would harvest energy or to better utilize energy in an ef?cient manner. The present monograph, WOLEDs and Organic Photovoltaics – Recent Advances and Applications, focuses on a very important and timely subject of topical interest that deals with the more ef?cient use of energy through white organic light-emitting diodes (WOLEDs) for solid-state lighting and the development of clean sources of renewable energy through the harvesting of light energy for conversion into electrical energy in organic photovoltaics. While LED solid-state lighting and photovoltaics have been dominated by inorganic semiconductor materials and silicon-based solar cells, there have been growing interests in the development of WOLEDs and organic photovoltaics.