Hall effect in the accumulation layers on the surface of organic   semiconductors
  We have observed the Hall effect in the field-induced accumulation layer on the surface of small-molecule organic semiconductor. The Hall mobility mu_H increases with decreasing temperature in both the intrinsic (high-temperature) and trap-dominated (low-temperature) conduction regimes. In the intrinsic regime, the density of mobile field-induced charge carriers extracted from the Hall measurements, n_H, coincides with the density n calculated using the gate-channel capacitance, and becomes smaller than n in the trap-dominated regime. The Hall data are consistent with the diffusive band-like motion of field-induced charge carriers between the trapping events. 
V. Podzorov, E. Menard, J. A. Rogers, M. E. Gershenson