1. International Technology Roadmap for Photovoltaic (ITRPV), http://www.itrpv.net/Reports/Downloads/.
2. Compulsive policy-making—the evolution of the German feed-in tariff system for solar photovoltaic power;Hoppmann;Res. Policy,2014
3. Opportunities of sustainable manufacturing in industry 4.0;Stock;Procedia CIRP,2016
4. For the latest version, see: https://en.wikipedia.org/wiki/Solar_cell_efficiency.
5. For the latest version, see https://spectrum.ieee.org/static/interactive-record-breaking-pv-cells.