The expected development of the internet of things (IoT) will rely on wireless sensor networks (WSN) formed by a large number of miniaturized sensor nodes that detect physical phenomena such as light, heat, pressure, acceleration, angular rate, etc. Powering these miniaturized sensors creates an increasing demand for smaller sources of renewable energy capable of delivering the required power characteristics (power, voltage, etc.). Photovoltaic (PV) cells are an attractive source of renewable energy for these sensors, but the output voltage of a single cell is limited. The aim of this project was to proof the concept of building CMOS and MEMS-compatible high-voltage micro-PV cells based on guided core-shell nanowire arrays on silicon connected in series. The idea derives directly from our ERC Advanced project "GuidedNW", where we demonstrated the surface-guided growth of different semiconductor nanowires on various flat and faceted single-crystal substrates via epitaxy or graphoepitaxy, respectively, and their integration into functional systems, including logic circuits, photodetectors and PV cells. During this PoC project we demonstrated: (1) The integration of several p/n-junction core-shell nanowire arrays in series to produce PV cells with multiplied output voltage, via epitaxial growth on sapphire. The guided growth of nanowires by artificial guides (artificial epitaxy) created by (2) nanolithography on silicon wafers, (3) mechanical scratching of silicon wafers and glass, and (4) imprinting of glass. (5) Guided growth of p/n-junction core-shell nanowires as in (1) has been demonstrated also on silicon wafers, and their integration into series-connected micro-PV cells is at an advanced stage. (6) A patent based on (1) and (2) has been filed. (7) A PCT patent has been filed based on the latter, plus (3) and (4). (8) A detailed market study has been carried out to assess the market potential of the innovation, better position ourselves in potential markets and analyze current potential opportunities. (9) Extensive contacts with industry have been established toward commercialization and identification of potential industrial partners. (10) The project has won the TechConnect 2019 Innovation Award at the TechConnect World Innovation Conference and Expo (June 17-19, 2019, Boston, MA). Overall, the project has demonstrated the feasibility and interest of guided nanowires for integration into miniature power sources for IoT. Considering the growing penetration of IoT into our everyday life, successful development of this promising technology could have a tremendous economic and societal impact.
