The experimental and theoretical search for cheap and abundant high performance semiconductors leads to increasingly complex multi-component materials. For materials with applications in photovoltaics,the optical properties are most important, but they mean little without control of the electronic properties. I will give an introduction to first-principles computations of intrinsic point defects and extrinsic dopants and the resulting charge carrier concentrations using the work of my research group on novel inorganic semiconductors, such as Bariumcopperfluoridechalcogenides (BaCuChF Ch={S,Se,Te}) and Copperphosphorselenide (CuP_3Ch_4) as examples. The target audience are students and researchers in physics, chemistry, and materials science who try to use the results of theoretical predictions in their work.