p-type transparent conducting chalcogenides

Transparent conducting materials are an important component in many optoelectronic devices ranging from solar cells to transparent electronics. A good transparent conducting material must allow high optical transmittance across a wide optical spectrum, requiring a large optical band gap (\textgreater 3.0 eV), and have high conductivity. However, in materials high conductivity and large band gaps usually do not coexist. At present, only a few materials are known to be reasonably good n-type transparent conducting oxides (TCOs). The p-type TCOs are still plagued by their poor hole conductivity, usually two orders of magnitudes lower than the highest electron conductivity in the n-TCOs. Chalcogenides usually have better hole conductivity, but their band gaps are usually too small. In this study, first-principles calculations are used to design new chalcogenides with large band gaps. New ternary chalcogenides, i.e.,Cs$_{2}$Zn$_{3}$Se$_{4}$ and Cs$_{2}$Zn$_{3}$Te$_{4}$, are found by calculations to be chemically stable and have both large band gaps (\textgreater 3.0 eV) and small effective masses. These new ternary chalcogenidesare are synthesized and found to be air stable.