Upconversion Luminescence: Transition Metal‐Involved Photon Upconversion (Adv. Sci. 12/2016)

Wavelength‐tuneable single‐band upconversion (UC) can be achieved in some transition metal ion (TMI) activated systems ascribed to the susceptibility of d‐electrons to the chemical environment. Moreover, UC of lanthanide ions (Ln(3+)) can be modulated by TMI, which benefits from the specific metastable energy levels of Ln(3+) owing to the well‐shielded 4f‐electrons and tuneable energy levels of TMI. The combination also brings out additional functions like antiferromagnetism, ferroelectricity, and oxide‐ion conductivity as well. Recent advances in this research field are reviewed in article 1600302 by Shi Ye, En‐Hai Song, and Qin‐Yuan Zhang. [Image: see text]