Layered transition metals dichalcogenides (TMD) are promising candidates for exploring atomically thin structures. Bulk crystals are semiconductors with an indirect gap in the near infrared spectral range. In contrast, monolayer dichalcogenides such as MoS2, WS2 or WSe2 are 2D semiconductors with a direct gap in the visible spectral range [1 and references therein]. This work concerns the nonlinear-optical properties and photoluminescence (PL), including spectroscopy in high magnetic fields (B< 30T), of 2H-WS2, 2H-WSe2, 2H- and 3R-MoS2 bulk crystals and 2D flakes intercalated with halogen molecules, caused by direct gap emission with both neutral and charged exciton recombination, as well as by bound excitons emission provided by means of intercalation of halogen molecules into the van der Waals gap [2]. The single crystals were grown through the chemical-vapor method, using iodine, bromine and chlorine as transport agents. Single- and few-layer flakes of TMD have been obtained by mechanical exfoliation of bulk crystals. Thin TMD flakes exfoliated on a silicon substrate have been studied using optical second harmonic generation (SHG) microscopy. The influence of polytypism of the investigated samples (i.e. of 3R non-centrosymmetric and 2H centrosymmetric polytypes) is discussed. The presence of two polytypes in the MoS2 samples was confirmed by the spectral structure of the PL of bound excitons observed in flakes at low temperature.