For adjusting the carrier concentrations, we would expect the π phases to have similar defect chemistry to the orthorhombic phases. Applying similar principles to the above, we might favour dopants that do not form cubic chalcogenide phases, and thus of the two common dopants used for the p-type orthorhombic phases Ag may be preferable to Na. For n-type doping we might consider Group V elements such as Bi and Sb, since the sesquichalcogenides adopt orthorhombic and rhombohedral phases. We note, however, that if the π phases are kinetically formed, then the effect of potential dopants on the kinetics of formation may need to be considered. This is very difficult to address computationally, and we feel it may be better approached experimentally.