Solar Cell Photo-Luminescence Modulation for Optical Frequency Identification Devices

This paper presents a wireless optical communication scheme that uses solar cells to transmit information. Transmission of information with a solar cell is possible by exploiting the fact that high-efficiency solar cells are also good at emitting light. These emissions, called luminescent emissions, are a function of the voltage across the cell. Here, we take the advantage of this fact to modulate the luminescent emissions of a GaAs solar cell to transmit information. We call devices that use this type of communication optical frequency identification devices. A circuit model of a solar cell that includes luminescent emissions is presented along with a circuit that modulates the photo-luminescent radiation emitted by a solar cell while harvesting energy from it. An analysis of this circuit is presented and employed to suggest different modulation strategies. A prototype of the modulator was built and tested. Test results show good agreement with the circuit analysis. It is also shown how the proposed circuit can be used to implement pulse amplitude modulation and ON-OFF keying modulation. Experimental results show that the proposed communication system achieves a bit error rate of 1.6 × 10
^-3
at a rate of 10 kb/s and at a distance of 50 cm.