High‐efficiency photovoltaic modules on a chip for millimeter‐scale energy harvesting

Abstract

Photovoltaic modules at the millimeter scale are demonstrated in this work to power wirelessly interconnected millimeter-scale sensor systems operating under low-flux conditions, enabling applications in the Internet of things and biological sensors. Module efficiency is found to be limited by perimeter recombination for individual cells and shunt leakage for the series-connected module configuration. We utilize GaAs and AlGaAs junction barrier isolation between interconnected cells to dramatically reduce shunt leakage current. A photovoltaic module with eight seriesconnected cells and total area of 1.27 mm 2 demonstrates a power conversion efficiency of greater than 26% under low-flux near-infrared illumination (850 nm at 1 μW/mm 2 ). The output voltage of the module is greater than 5 V, providing a voltage up-conversion efficiency of more than 90%. We demonstrate direct photovoltaic charging of a 16-μAh pair of thin-film lithium-ion batteries under dim light conditions, enabling the perpetual operation of practical millimeter-scale wirelessly interconnected systems.

Bridging the “Last Millimeter” Gap of Brain-Machine Interfaces via Near-Infrared Wireless Power Transfer and Data Communications

“…To prevent PV cell degradation while μLEDs are forward biased, AlGaAs junction barrier layers are incorporated in the epitaxial structure to achieve electrical isolation, based on a strategy we have used previously for monolithic PV arrays. 32 The full epitaxial structure for the PV/μLED device and data related to device operation are provided in Supporting Information (Table S1 and Figures S1−S3). The device fabrication process incorporates a series of chemical surface treatments using ammonium hydroxide and ammonium sulfide 33,34 and thin film passivation to minimize nonradiative losses at the device perimeter.…”

“…The μLED uses an In 0.2 Ga 0.8 As multi quantum-well (QW) structure with doping profiles that are optimized to achieve high internal radiative efficiency at low current levels , and lateral current spreading to improve light extraction efficiency for small layer thickness. To prevent PV cell degradation while μLEDs are forward biased, AlGaAs junction barrier layers are incorporated in the epitaxial structure to achieve electrical isolation, based on a strategy we have used previously for monolithic PV arrays . The full epitaxial structure for the PV/μLED device and data related to device operation are provided in Supporting Information (Table S1 and Figures S1–S3).…”

Energy Harvesting in Nanosystems: Powering the Next Generation of the Internet of Things

“…Energy harvesting can be readily achieved using photovoltaic (PV) cells designed for ambient outdoor or indoor lighting, or additional illumination sources. PV cells can directly provide an operating voltage on the order of 0.5 V, depending on the illumination source and PV cell technology, which may be increased through series connections (Moon et al, 2019) or tandem cell designs (Moon et al, 2020). Scaling down device dimensions below 1 mm can reduce conversion efficiency due to perimeter non-radiative recombination effects in semiconductors (Moon et al, 2017), where passivation of semiconductor surfaces remains a key to achieving high energy conversion efficiency.…”

Dust‐Sized High‐Power‐Density Photovoltaic Cells on Si and SOI Substrates for Wafer‐Level‐Packaged Small Edge Computers

“…In prior works, the integration process was done using nonmanufacturable processes, including chip stacking and wire bonding between chips. [ 7,17–22 ] A high‐throughput manufacturable process was not demonstrated. It is expected that the small edge computing system has a low cost because the number of chips per wafer is very large.…”