[18] <best-research-cell-efficiencies.Pdf>. https://www.nrel.gov/pv/assets/pdfs/best-research-cell-efficiencies.pdf
[64] A.K. Geim, I.V. Grigorieva, Van der waals heterostructures. Nature 499, 419–425 (2013).
[153] R.W. Keyes, The electrical properties of black phosphorus. Phys. Rev. 92, 580–584 (1953).