High‐Efficiency Indoor Photovoltaic Energy Harvesting

Abstract

An indoor photovoltaic energy harvesting device technology has been developed that achieves high efficiencies and high power per area at low light levels. A 50 mm x 20 mm energy harvesting device comprising a compound semiconductor material is demonstrated. At 200 lux white LED illumination (CCT 2,831 K), its operating power at maximum power point is 170.0 μW with Voc = 4.61 V and Isc = 43.8 μA, corresponding to an active area power density of 21.8 μW/cm2. Based on this high-efficiency energy harvesting device, an indoor photovoltaic (PV) energy harvesting power module (IPEHPM) has been developed for autonomously powering IoT sensor nodes and other devices which ordinarily would require disposable or user-rechargeable batteries to operate. The IPEHPM can deliver 3.6 ~ 4.2 V output voltage, with 100 mA pulse current for up to 600 ms. An average energy harvester to storage efficiency of 88.7% has been demonstrated at 200 lux. We demonstrate that the IPEHPM is suitable for perpetually powering a wireless building automation CO2 sensor node at 200 lux, with CO2 measurement and data transmission every 150 s. Applications of high-efficiency energy harvesting devices in wearables and in wireless beacons are also discussed.