Validity of Transport Energy in Disordered Organic Semiconductors
  A systematic study of the transport energy in disordered organic semiconductors based on variable range hopping theory has been presented here. The temperature, electric field, material disorder and carrier concentration dependent transport energy is extensively discussed. We demonstrate here, transport energy is not a general concept and invalid even in low electric field and concentration regime. 
Ling Li, Nianduan Lu, and Ming Liu
cond-mat.dis-nn