Two-dimensional semiconductors show great promise for next-generation (opto)electronics, yet a number of issues have to solved  before realizing their full potential. Here by using atomistic theory, we show that: (i) The harmful electronic states induced by chalcogen vacancies can be removed by chemisorption of oxygen molecules. This reaction occurs with a barrier that correlates with the cohesive energy of the semiconductor. The repair of the electronic structure originates from the isovalence between O₂ and X when bonded with metal. Based on these findings, we propose an approach to improve the performance of 2D semiconductors by using O2 to passivate the defects. ^[1] (ii) The problem of large and untunnable Schottky barrier at the metal–semiconductor interface can be solved with new electrode materials. ^[2]

[1] Y. Liu, P. Stradins, S. Wei, Angew. Chem. Int. Ed. 2015, DOI: 10.1002/anie.201508828; [2] Y. Liu, P. Stradins, S. Wei, submitted