Effect of oxygen on the electrical characteristics of field effect transistors formed from electrochemically deposited films of poly(3-methylthiophene)

Abstract

Field effect devices have been formed in which the active layer is a thin film of poly(3-methylthiophene) grown electrochemically onto preformed source and drain electrodes. Although a field effect is present after electrochemical undoping, stable device characteristics with a high modulation ratio are obtained only after vacuum annealing at an elevated temperature, and only then if the devices are held in vacuo. The polymer is shown to be p type and the devices operate in accumulation only. The hole mobility in devices thermally annealed under vacuum is around 10-3 cm2 V-1 s-1. On exposure to ambient laboratory air, the device conductance increases by several orders of magnitude. This increase may be reversed by subjecting the device to a further high-temperature anneal under vacuum. Subsidiary experiments show that these effects are caused by the reversible doping of the polymer by gaseous oxygen.

An experimental study on the molecular organization and exciton diffusion in a bilayer of a porphyrin and poly(3-hexylthiophene)

“…This indicates that the concentration of ionized impurities in the P3HT layer is either in the same order of magnitude or is lower than the concentration in the H 2 TMPyP layer. The presence of mobile holes in P3HT layers is generally attributed to reversible doping with oxygen, [41][42][43][44] while the origin of the excess mobile electrons in the H 2 TMPyP layer is not clearly established. 45 The internal electric field present over the interface between H 2 TMPyP and P3HT is expected to retard interfacial recombination of electrons and holes formed on exciton dissociation.…”

Effects of space charge at the conjugated polymer/electrode interface

“…Following our previously reported procedures 8,20,21 deposition of the polymer was carried out in two stages; a short nucleation step, in which 2.0 V (vs. Ag) was applied to the working electrode for 10 s, followed by the main growth step when the potential was reduced to 1.6 V (vs Ag) and applied for the time necessary to grow a film of predetermined thickness. Subsequently, the film was dedoped, i.e.…”

“…8 The In a further series of experiments, a number of subtle changes were observed in the admittance plots upon increasing the thickness of the polymer film from 60 to 120 nm (achieved by increasing the growth time from 60 to 600s):…”

“…Significant progress has been achieved also in developing active polymer devices and even integrated circuits [7][8][9][10][11] in which the carrier mobility is comparable with that in amorphous silicon 12 . The polymers utilised to date have relatively high bandgap, ca.…”

EFFECT OF AMBIENT AIR CONDITIONS ON LOW FREQUENCY NEGATIVE CAPACITANCE OF NC-TIO₂/P3HT HETEROJUNCTION SOLAR CELLS

“…In the last decades, many researchers have used small-signal admittance techniques to identify microscopic processes in electronic devices, for example, charges recombination and generation at interfacial areas such as metal/semiconductor or semiconductor/insulator (Zaki et al, 2013;Itoj and Nakagoshi, 2014;Taylor et al, 1991;Stallinga et al, 2002). The interface and bulk region of solar cells extend only few hundred nanometer and their properties affect on the devices performance and stability (Jørgensen et al, 2008;Rahid et al, 2013).…”