Metal sulfides (MeS₂) such as MoS₂ and WS₂ were used as charge transport layers in organic light-emitting diodes (OLEDs) and organic photovoltaic (OPV) cells in order to enhance the stability in air comparing to poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). MeS₂ layers with a polycrystalline structure were synthesized by a chemical deposition method using uniformly spin-coated (NH₄)MoS₄ and (NH₄)WS₄ precursor solutions. The ultraviolet-ozone (UV-O₃) treatment on MeS₂ leads to the removal of the surface contaminants produced by the transfer process, resulting in a uniform surface and an increase of the work function. The maximum luminance efficiencies of the OLEDs with UV-O₃-treated MoS₂ and WS₂ were 9.44 and 10.82 cd/A, respectively. The power conversion efficiencies of OPV cells based on UV-O₃-treated MoS₂ and WS₂ were 2.96 and 3.08%, respectively. These values correspond to over 95% of those obtained with (PEDOT:PSS) based devices. Furthermore, OLEDs and OPV cells based on MeS₂ showed two to six times longer stability in air compared with PEDOT:PSS based devices. These results suggest that UV-O₃-surface-treated MeS₂ could be a promising candidate for a charge transport layer in optoelectronic devices.