Electronic states at conducting polymer/conducting oxide interfaces observed using a low-energy photoelectron spectroscopic method

Abstract

We have observed the electronic states at conducting polymer/conducting oxide interfaces using a low-energy photoelectron spectroscopic method. The electronic states of conducting polymer/indium tin oxide (ITO) interfaces were different from those of conducting polymer/metal interfaces. The electron transfer from a conducting polymer to ITO occurred at the interfaces, and is not related to the difference of the ionization potential between conducting polymers and ITO. Although the origin of this electron transfer is not clear at this stage, we speculate that the surface states of ITO play a major role. Moreover, the electron transfer at the interfaces is enhanced at higher temperatures. Other conducting oxides such as indium oxide (In2O3) and tin oxide (SnO2) also show a similar tendency to that of ITO.

Illumination induced charge separation at tetraphenyl-porphyrin/metal oxide interfaces

“…The peak of the Q 1 transition ͓Q x ͑0,0͔͒ is masked by charging and discharging processes that can be related to the influence of interactions with interface states at organic/ metal oxide heterojunctions. [6][7][8] The kinetics of charging and discharging of the H 2 TPP layer below the HOMO-LUMO transition strongly depend on the temperature. This is demonstrated by the ⌬CPD spectra shown in Fig.…”

“…Additionally, mainly oxygen, but also metal atoms, may diffuse from the substrate to the organic film, altering the interface electronic structure. 6,7 Nakanishi et al 8 found that electron transfer from the conducting polymer to indium tin oxide ͑ITO͒, In 2 O 3 , and SnO 2 substrates occurred at the interfaces. Although the origin of this electron transfer is not clear, the authors speculate that the surface states of the substrate play a major role.…”

Dependence of charge carrier injection on the interface energy barrier in short-channel polymeric field effect transistors

“…Such behavior would be consistent with previous results and has typically been explained using a simple rigid-band picture, in which the similarity of the ionization potential of P3HT (e/ i ¼ 4.7 eV) with (A M $ 5 eV) of metals such as Co or Au leads to the absence of an interface energy barrier. 9,10 In this case, the Fermi level in the metal is aligned with the top of the valence band in the polymer; hence, the contact is transparent for hole-injection. 11,12 However, band offsets can be hidden by the thermal excitation of charge carriers at room temperature, and consequently, a low-temperature study is necessary to discern the real nature of contact resistance.…”

Modeling of Electronic Transport through Metal/Polymer Interfaces in Thin Film Transistors

“…Similarly, the contact resistance has been interpreted in terms of thermionic emission in [3,5,10,11]. The formation of an interface Schottky barrier is indeed well documented by photoemission measurements [12,13]. The tuning of the Schottky energy barriers by attaching oriented dipoles layers on top of the metal contacts has also been performed in [14], which undoubtedly proves the presence of these potential barriers.…”