Organic Polymers with Tunable Charge Carrier Mobilities

Abstract

ABSTRACTCharge carrier (hole) mobility in amorphous organic polymeric materiats can be changed at will over at least nine orders of magnitude without increasing the conductivity of the polymers, and also without affecting the carrier range, i.e., without introducing deep traps. The changes in the drift mobility can be accomplished by several means: (1) by changing the density of hopping sites (the concentration of transport-active molecules or groups), (2) by light doping the host polymer with low-oxidation potential compounds (for hole transport), and, eventually, (3) by the nature of the host medium and its polarity. Since the carrier mobility is typically activated and electric field dependent, significant changes can also be made by varying the temperature and the electric field. An enhancement of mobility by heavy doping has also been described. Hole mobilities in the small molecule - host polymer composites and also in polymers in which the transport states are backbone-derived can thus be varied from values below the measurement threshold (<10−10 cm2 V− s−1) to fairly high values in the neighborhood of 10−1 cm2 V−1 s−1 at an electric field of E = 105 V cm−1 and at 295 K.