A portable electronic device with large display screen-to-body includes a housing, a first display, a circuit board, and an optical module. The first display is a transparent display. The optical module is electrically connected to the circuit board and positioned below the first display. The first display, the optical module, and the circuit board are received in the housing, the optical module is configured to receive external light passing through the first display even as the first display is displaying images. Operating methods for the portable electronic device in various modes are also provided.