Charge TransferTransition metal dichalcogenides (TMDCs) belong to the class of various 2D materials which in bulk form are composed of strongly bonded layers with week van der Waals force among them, [1][2][3] allowing exfoliation into atomically thin layers whose properties can be distinct from their bulk counterparts. [1,4,5] TMDCs show a wide range of electronic, optical, mechanical, chemical, and thermal properties which have been studied for decades. [4] Intercalation of TMDCs is one important field in the chemistry of inclusion compounds. With guest materials such as alkali metals intercalated in the host ones, the structure Figure 4. Schematic illustration of the phase transition. a) structure of 2H-Na 0.5 MoS 2 and valence state of Mo. b) Schematic showing charge transfer between Mo 3+ and Mo 4+ and the charge transfer induced phase transition from 2H to 1T. www.advancedsciencenews.com