Low Illumination Light (LIL) Solar Cells: Indoor and Monochromatic Light Harvesting
ARMY RESEARCH LAB ADELPHI MD SENSORS AND ELECTRON DEVICES DIRECTORATE
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Low and indoor light energy harvesting is needed to meet the demands of zero net energy ZNE building, Internet of Things IoT, and indirect energy conversion isotope battery IDEC iBAT systems. Characterizing photovoltaic PV solar cells under low intensity and narrow light spectrum conditions has not been clearly examined. PV operating values under 1 sun illumination do not scale linearly under low intensity and monochromatic light conditions efficiency drops from 30 to 3 at 1 Woptcm2. However, limited energy conversion efficiencies and metrics can be improved by choosing a PV whose band gap matches the light source. By quantifying losses on single-junction semiconductors, we can determine the theoretical maximum efficiency of a PV material for different light sources. We measure single-junction solar cells parameters under 3 different white light indoor light and near monochromatic light spectrum sources with light intensities ranging from 0.5 to 100 Woptcm2. Measurements show that indium gallium phosphide InGaP has the highest surface power density and conversion efficiency 29 under 1 Woptcm2 at 523 nm for 470-nm, 523-nm, and white light. The results will aid the US Army s decision on selecting the best PV type for the IDEC iBAT and other energy harvesting systems.
- Non-electrical Energy Conversion