Energy harvesting photodiodes with integrated 2D diffractive storage capacitance

Integrating photodiodes with logic and exploiting on-die interconnect capacitance for energy storage can enable new, low-cost energy harvesting wireless systems. To further explore the tradeoffs between optical efficiency and capacitive energy storage for integrated photodiodes, an array of photovoltaics with various diffractive storage capacitors was designed in TSMC´s 90 nm CMOS technology. Transient effects from interfacing the photodiodes with switching regulators were examined. A quantitative comparison between 90 nm and 0.35 μm CMOS logic processes for energy harvesting capabilities was carried out. Measurements show an increase in power generation for the newer CMOS technology, however at the cost of reduced output voltage.