An energy-harvesting system capable of wireless communication is disclosed which includes a solar cell adapted to generate charge from incident light on the solar cell; an energy-harvesting circuit coupled to the solar cell, the energy-harvesting circuit adapted to convey charge from the solar cell to an energy reservoir; a data communication circuit adapted to encode data to be communicated by the solar cell by adjusting the voltage across the solar cell into at least two states including 1) an open circuit (OC) state, where the current through the solar cell is substantially zero, and 2) a maximum power point (MPP) state, where power (V×I) drawn from the solar cell is maximum, wherein the solar cell in response to the changes in its voltage and the incident light emits luminescent radiation with an intensity corresponding to the at least two states, thereby forming a wireless transmitter.