Optical films for enhancing light extraction from self-emissive light sources such as bottom-emitting or top-emitting OLEDs are disclosed. The extraction films typically include a flexible carrier film, and a first and second layer carried by the carrier film. The first or second layer has a nanovoided morphology and includes a polymer binder, and may also have a refractive index less than 1.35 or 1.3. An embedded structured surface of light extraction elements is formed between the first and second layers. The light extraction elements may be primarily diffractive elements adapted to be disposed within an evanescent zone of the OLED, or they may be primarily refractive elements adapted to be disposed outside the evanescent zone. The extraction film may also include a third layer, and a second embedded structured surface may be formed between the third layer and the first layer.