1. https://en.wikipedia.org/wiki/Solar_energy.
2. United Nations Development Programme and World Energy Council, Energy and the challenge of sustainability, 2000.
3. 2014 Key World Energy Statistics, (2014) 6, 24, 28. http://www.iea.org (Accessed May 5, 2014).
4. http://www.inforse.org/europe/dieret/Solar/solar.html.
5. Organometal halide perovskites as visible- light sensitizers for photovoltaic cells;Kojima;J. Am. Chem. Soc.,2009