Controlled doping of phthalocyanine layers by cosublimation with acceptor molecules: A systematic Seebeck and conductivity study

Abstract

We investigate the doping of vanadyl–phthalocyanine by a fluorinated form of tetracyano-quinodimethane as an example of controlled doping of thin organic dye films by cosublimation of matrix and dopant. The electrical parameters of the films derived from conductivity and Seebeck measurements show that the results largely follow standard models used to describe the doping of crystalline semiconductors; e.g., a smooth shift of the Fermi level towards the valence states with increasing doping is observed. Other effects, like the superlinear increase of conductivity with the molar doping ratio, need the inclusion of additional effects like percolation.

Optical measurement of doping efficiency in poly(3-hexylthiophene) solutions and thin films

“…[5][6][7] P-type doping, for instance, involves introducing an acceptor molecule with a lowest unoccupied molecular orbital (LUMO) lower in energy than that of the highest occupied molecular orbital (HOMO) of the donor, which results in an electron transfer between the dopant and the host material. [8][9][10] Over the past few decades, many studies have been aimed towards understanding such doping processes, many of which focused on answering two questions: what is the nature of the generated charge (polarons, bipolarons, free carriers or is a strongly bound complex formed) and how efficiently does a dopant molecule generate these species. These two questions are widely discussed but not yet completely answered.…”

Investigation of the High Electron Affinity Molecular Dopant F6‐TCNNQ for Hole‐Transport Materials

“…The Spiro-TAD conductivity increases by more than two orders of magnitude with 5.0 mol% F6-TCNNQ. All the conductivity plots vs T follow an Arrhenius relationship (Figure 7c), which allows the determination of the activation energy E a using Equation (1). The dependence of E a on the dopant concentration is shown in Figure 7d.…”

“…The IE and EA of the F6-TCNNQ film, defined as the energy difference between E VAC and the HOMO and LUMO edge, are 7.53 and 5.60 eV, respectively. The F6-TCNNQ EA is therefore 350 meV larger than its F4-TCNQ counterpart, [1] and about equal to that of another powerful p-dopant, Molybdenum tris-[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd) 3 ), [10] pointing to its strong oxidizing potential.…”

“…[1][2][3][4] Conceptually, p-doping is realized by charge transfer from the highest occupied molecular orbital (HOMO) of the host material to the lowest unoccupied molecular orbital (LUMO) of the dopant. For a one-electron oxidizer, this charge transfer becomes energetically favorable when the electron affinity (EA) of the dopant is about equal to, or is larger than, the ionization energy (IE) of the host.…”

Role of band states and trap states in the electrical properties of organic semiconductors: Hopping versus mobility edge model

“…In analogy to inorganic semiconductors, the control of charge carrier concentration in organic semiconductors can be achieved by means of molecular doping [47][48][49][50][51][52] . Here, we apply both hopping and ME models to interpret the recent experimental data reported for n-doped C 60 films.…”