Electroluminescence in Single Layer MoS2
  We detect electroluminescence in single layer molybdenum disulphide (MoS2) field-effect transistors built on transparent glass substrates. By comparing absorption, photoluminescence, and electroluminescence of the same MoS2 layer, we find that they all involve the same excited state at 1.8eV. The electroluminescence has pronounced threshold behavior and is localized at the contacts. The results show that single layer MoS2, a direct band gap semiconductor, is promising for novel optoelectronic devices, such as 2-dimensional light detectors and emitters. 
R. S. Sundaram, M. Engel, A. Lombardo, R. Krupke, A. C. Ferrari, Ph.   Avouris, M. Steiner
cond-mat.mes-hall cond-mat.mtrl-sci