Abnormal Temperature Dependence of Mobility in a Disordered System With Traps: Experiment and Theory

Mobility μ is essential in electronic and optoelectronic devices. Abnormal temperature T dependence of the carrier mobility μ of poly [2-methoxy-5-2-ethyl-hexyloxy]-p-phenylenevinylene (MEH-PPV)/InP nanocrystal composites was observed using the time-of-flight technique. The slope of ln(μ) as a function of 1/T² dramatically changed before and after the critical temperature T_c of 283 K. Using the variable range hopping theoretical mode, a new trap-filling factor (FF) was proposed as a key parameter to illustrate the effect of the trap on the mobility. According to FF, there are three regions. When FF ≫ 1 and FF≪1, the carrier behavior follows the Fermi and Boltzmann distributions, respectively. When FF~1, the derived transition temperature of 282.4 K represents a transition point from Fermi to Boltzmann distribution, which is consistent with T_c in the experiment. Finally, a universal dependence of ln(μ) on T was concluded based on FF in a disordered system with traps.