Intrinsic ambipolar transport for the traditional conducting or hole transport ionic blend polymer PEDOT:PSS

Abstract

In traditional viewpoint, poly-3,4-ethylenedioxythiophene: polystyrenesulfonate (PEDOT:PSS) in solid state photoelectronic device is considered to be conducting or hole transporting polymer. So at the beginning, this work researched the conducting mechanism of PEDOT:PSS, which leads to that the PEDOT:PSS should not be good conductor. Then one simple model is used to theoretically analyse the carrier dynamics, and its results show that PEDOT:PSS should be ambipolar polymer in theory. Based on the theory, the hole- and electron-only diodes fabricated by PEDOT:PSS are investigated through the impedance spectroscopy method, and such experimental data fully proved the theoretical results. Besides the ambipolar characteristic, mobility verse E1/2 curves show the abnormal negative slopes, that hole and electron mobilities decrease with the increment of biased electric field, which is not in accordance with the common standpoint that the charge carrier should be accelerated by electric field. Thus such experimental data in further propel us to propose the concepts of HOMO trap and LUMO trap, which exists in the energy space of frontier orbital and decelerates the movement of charge carrier.