Abstract: An electrical-energy storage system for storing electrical energy received from an energy harvesting power supply source and for delivery of stored energy to an application load comprises an input N21 for receiving electrical energy from the energy harvesting power supply source. The system comprises a first electrical-energy storage unit having a first storage capacity and a second electrical-energy storage unit having a second storage capacity, greater than the first storage capacity. It comprises an output N22 for providing electrical energy from the second electrical-energy storage unit to the application load.

Abstract: An electronic device comprises a photovoltaic unit, an energy storage unit, a voltage detector, a load switch and an application load. The device is configured to harvest and store energy from ambient illumination, and to optimise power delivery to the application load from at least one of the harvested energy and the stored energy. The photovoltaic unit, the energy storage unit, the voltage detector and an input of the load switch are connected to a common point. The photovoltaic unit harvests energy from the ambient illumination. An output of the load switch is coupled to the application load. The voltage detector measures a voltage at the common point and turns on the load switch when the measured voltage has increased to a level that is greater than or equal to a first voltage, in order to provide optimised power delivery to the application load from at least one of the energy storage unit and photovoltaic unit.

Abstract: A photovoltaic energy harvesting (PVEH) device comprises a single-junction photovoltaic cell. The photovoltaic cell includes a light converting element made of a wide band-gap III-V active material spectrally matched to an ambient light source, a light receiving side that is free from front metal contact gridlines, and at least one discrete metal contact element placed on the light receiving side that realizes power extraction. The active material of the light converting element may be made of (Al)GaInP compounds. The active material of the light converting element may be spectrally matched to ambient light in the form of at least one of an artificial light source and natural sunlight, and combinations thereof. The PVEH device may have a plurality of photovoltaic cells inter-connected in series to achieve a higher open-circuit voltage. A total fractional power loss due to series resistance, shunt resistance and contact shading is less than 20%.

Abstract: A multi-junction photovoltaic structure which includes a first photovoltaic sub-cell having at least one junction, a second photovoltaic sub-cell having at least one junction and having a band gap smaller than a smallest band gap of the first photovoltaic sub-cell, and an interlayer that provides optical coupling between the first and second photovoltaic cells, wherein the interlayer has a physical thickness substantially similar or less than a vacuum wavelength of light corresponding to a smallest band gap of the second photovoltaic sub-cell.