Field-induced polarization effect on space charge limited current in the charge transport of poly(-3octylthiophene) thin films

Abstract

Herein, the effects of field-induced polarization on electrical charge transport of poly(3-octylthiophene) (P3OT) thin films are elucidated. The current-density versus voltage (J-V) characteristics of P3OT thin films were studied as a function of temperature (110–290 ​K), thickness (120–800 ​nm), and field-induced polarization in the hole-merely device setup. The data, so-obtained, were examined in terms of space charge limited conduction (SCLC) theory with the inclusion of shallow traps. The logJ-logV curves reveal explicitly two conduction regions, (i) Ohmic at low fields, and (ii) non–Ohmic at higher fields. The charge transport at higher-fields is credited to SCLC phenomena in the presence of shallow hole traps. The trap-density of 200 ​nm thick P3OT films is evaluated to be 8.04 ​× ​1023 ​m−3, which decreased with the increase of film thickness. The hole mobility is estimated to be 1.65 ​× ​10−6 ​cm2/V⋅s from the quadratic part of the SCLC region.