The doped solution was prepared by adding to the
precedent solution CoCl3·4H2O or InCl3 as dopant
source. The weight percentages of (Co/Zn) and (In/Zn)
were 1, 2, and 3 for ZnO:Co and 2, 3, and 4 for ZnO:In.
The solution became clear and homogeneous after stirring for 120 min at 50 to 70°C.