Harvesting the available forms of energies in the environment to create self-powered nanosystems is now becoming a technological reality. Self-powered nanodevices and nanosystems are expected to play a crucial role in the future development of nanotechnology because of their specific role in fundamental studies and nanotechnological applications, mainly due to their size-dependent properties and independent, sustainable, maintainance-free operation. As a new field in self-powered nanotechnology-related research, self-powered photodetectors have been developed which exhibit a much faster photoresponse and higher photosensitivity than the conventional photoconductor-based photodetectors. Herein, the energy-havesting techniques are discussed and their prospects for application in self-powered photodetectors are summarized. Moreover, potential future directions of this research area are highlighted.