Sanchez T.G., Regalado-Pérez E., Mathew X., Sanchez M.F., Sanchez Y., Saucedo E., Mathews N.R. "Ge doped Cu2ZnSnS4: An investigation on absorber recrystallization and opto-electronic properties of solar cell" Solar Energy Materials and Solar Cells 198, pp. 44 - 52. 2019