Electronic structure of interfaces with conjugated organic materials

Abstract

The function and efficiency of most organic electronic and opto‐electronic devices greatly depend on the electronic structure of the interfaces therein. Charge injection from electrical contacts into the organic semiconductor, charge extraction, or exciton dissociation at organic semiconductor heterojunctions are crucial processes that must be optimized for high device efficiency. Consequently, the energy levels at these interfaces must be matched to allow for optimal performance. The key mechanisms that determine the energy level alignment at organic/electrode and organic/organic interfaces are reviewed, and methods to adjust the levels at such interfaces are presented. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Solution-processed quantum dot light-emitting diodes with PANI:PSS hole-transport interlayers

“…This suggests that the insertion of the PANI:PSS interlayer improved the device performance of the QD-LEDs. It is well known that the underlayer surfaces (e.g., the ITO and organic layers) strongly influence the morphology [42], molecular crystal structure, and optical and electrical properties of the organic overlayers [43][44][45]. The different crystallographic orientation of the molecules in the films [46] determines the interactions between neighboring chains, the electronic band structure, the optical properties [47], and the interface (or surface) electrostatic potential or electronic energy barrier of the organic films [48][49][50].…”

Photoelectrochemical properties of porphyrin dyes with a molecular dipole in the linker

“…10 A concept that is attracting increasing attention is that the energy level alignment of any interface at equilibrium is shifted, relative to its component native band edges, due to an intrinsic interface dipole (IID). 3,4,[11][12][13][14][15] For example, at the semiconductor/molecule interface, the IID effect has been shown responsible for attenuation of the conduction-band edge populations of TiO 2 and the LUMO of surface bound organic semiconductors. 16 This has been explained by equilibration of the TiO 2 semiconductor Fermi level with the adsorbed molecule's redox potentials.…”

Lateral band formation and hybridization in molecular monolayers: NTCDA on Ag(110) and Cu(100)

“…In the case of large π -conjugated molecules, a multitude of publications report on interfaces to different metals. [5][6][7][8][9][10][11] Some parameters such as charge injection barriers or ionization potentials can be straightforwardly determined from photoelectron spectroscopy (PES). [12][13][14] Moreover, the bonding at metal-organic interfaces also leads to the generation of novel states, 5,[15][16][17][18][19] which are due to the hybridization of metal and molecular wave functions.…”