US Patent 9837852 Harnessing front light in e-readers to generate electricity

An electronic device with a e-paper display that internally integrates photovoltaic cells and are not apparent from the exterior of the device. A light source of the device injects light into a light guide to front-light the e-paper. Light that leaks from edges of the light guide is captured by the photovoltaic cells. The plastic light guide is also impregnated with a photoluminescent material that absorbs near infrared energy that is incident on a face of the display and re-emits it isotropically to be guided by the light guide to the photovoltaic cells. By combining multiple techniques to illuminate hidden photovoltaic cells, the utility of the hidden cells is maximized.