Degenerate semiconductors in the light of electronegativity and chemical hardness

A model is proposed for the formation of degenerate semiconductors used as transparent electrodes. We propose that a degenerate semiconductor is, hypothetically, an oxide of formula Mⁿ⁺O_n/2 doped with an oxide of formula (Mⁿ⁺¹+e)O_n/2. In this formula, Mⁿ⁺¹ and e symbolizes, respectively, the ionized donor center and the associated conduction-band electron. The electron affinity of both the matrix and the dopant have to be adjusted in order to combine an important transparency and conductivity. The calculation of the electron affinity is calculated on the basis of the electronegativity and of the chemical hardness of the oxides. An excellent fit is obtained for the already known materials and the model permits to forecast new materials.