Temperature dependence of the charge injection in poly-dialkoxy-p-phenylene vinylene

Abstract

The injection of holes from a Ag electrode into poly-dialkoxy-p-phenylene vinylene is investigated by measuring the current–voltage characteristics as a function of temperature. For this model system, the hole injection is hindered by a contact energy barrier of about 1.0 eV. The observed temperature dependence of the injection-limited current does not agree with the predictions of classical injection models. A recent model, in which the spread in the charge transporting site energy due to disorder is taken into account, consistently describes the measured field and temperature dependence of the injection process.

Electro-optical properties of a polymer light-emitting diode with an injection-limited hole contact

“…5,6 In a recent experimental study, however, it has been demonstrated that hole currents from silver and aluminum into OC 1 C 10 -PPV exhibit a very weak temperature dependence, in spite of the presence of a large injection barrier of 1 eV. 7 This behavior is in contrast with the thermionic emission model which predicts a strong thermal activation, dominated by the large injection barrier. The field and temperature dependence of the injection-limited ͑IL͒ current is consistently explained by an injection model based on injection into tail states of the energetic distribution of hopping sites.…”

“…It should be noted that such electron traps remain unfilled in an ITO/Ag/PPV/Ag hole-only device, and therefore do not play a role in the investigation of the injection-limited hole current. 7 We have incorporated electron traps in an interfacial layer extending a few nm from the contact. The effect of these traps is described by a single parameter that represents the ratio of free electrons n and trapped electrons n t ϭ n nϩn t .…”

“…4 An injection-limited ITO/Ag/OC 1 C 10 -PPV/Ca PLED ͑IL PLED͒ was then constructed, in which the ITO bottom contact has been covered by Ag. For the investigation of reduced hole injection from the Ag electrode, ITO/Ag/PPV/Ag devices were constructed 7 with an electron-blocking Ag top contact. In order to discriminate whether the current in the IL PLED is dominated by the ͑reduced͒ hole or the electron current, Yb/PPV/Ca electron-only devices were investigated as well.…”

Cathode dependence of the open-circuit voltage of polymer:fullerene bulk heterojunction solar cells

“…11 It was recently demonstrated that the injection limited current is well described by hopping of charge carriers from the Fermi level of the metal into energetically disordered localized states of the organic semiconductor. 9,10 According to this hopping-based model, the ILC is determined by four parameters; 9,10 the energy width of the density of localized states , the nearest hopping distance a, the dielectric constant ⑀ r , and finally the energy distance from the Fermi level of the electrode to the center of the Gaussian DOS of the PCBM transport states ͑i.e., the barrier height b ). From the field and temperature dependence of the electron mobility of PCBM ϭ0.073 eV and aϭ3.4Ϯ0.1 nm have been extracted.…”

Microcontact printing of self-assembled monolayers to pattern the light-emission of polymeric light-emitting diodes

“…The HOMO level of MEH-PPV is approximately 5.3 eV [20,27]. Therefore, the LEDs based on vapor deposited gold (Φ = 4.8 eV) demonstrate an injection limited hole current due to the mismatch of the HOMO level of MEH-PPV and the work function of gold.…”