Abnormal temperature dependence of mobility in conjugated polymer / nanocrystal composite: experiment and theory

Instead of normal non-Arrhenius relationship, the carrier mobility $ln({\mu})$ v.s. $1/T^2$ showed abnormal dependence in an MEH-PPV / InP nanocrystal composite system that a critical temperature $(T_c)$ behavior is prominent in temperature range of 233 K to 333 K. Here, in the model of variable range hopping theory, an analytical model is developed within a Gaussian trap distribution, which is successfully implemented on that phenomenon. The results show that Tc becomes the transition temperature as long as trap-filling factor (FF) ~1, which means a transition point from Boltzmann to Fermi distribution. Furthermore, the model predicts an universal relationship of $ln({\mu})$ on $1/T^2$ determined by FF in any disordered system with traps.