Annica Crispin

Transition between energy level alignment regimes at a low band gap polymer-electrode interfaces

The energy level alignment at interfaces between a low band gap conjugated polymer and various electrodes is investigated using ultraviolet photoemission spectroscopy. When the electrode work funct ...

Understanding the initial stages of polymer grafting on metals : A photoelectron spectroscopy study of acrylonitrile adsorption on transition metal surfaces

X-ray and UV photoelectron spectroscopies show that acrylonitrile is chemisorbed on iron, nickel and copper polycrystalline surfaces via the carbon and nitrogen atoms. Depending on the conditions u ...

Aluminum-barium interfaces on some processable poly(p-phenylene vinylene) polymers studied by photoelectron spectroscopy

Control of the deposition of metals on the surfaces of conjugated polymers determines the electronic properties of the electrical contacts. The detrimental effects arising from the physical vapor deposition of metal atoms on conjugated polymer surfaces can be controlled by using a carefully chosen intermediate ultrathin layer of a “protection material.” In particular, the influence of an intermediate layer of barium atoms on the chemical effects that occur when aluminum atoms are deposited on the surfaces on substituted poly(p-phenylenevinylene)s has been studied using x-ray and ultraviolet photoelectron spectroscopy. In order to render the results somewhat more general, a series of substituted poly(p-phenylenevinylene)s was used, each with bulky side groups containing at least one oxygen atom, and the results presented are generalized beyond one particular substituted polymer system.

Influence of dopant on the electronic structure of spiro-oligophenyl-based disordered organic semiconductors

The electronic structure of the propeller-shaped spiro-type molecules 2,2′, 7,7′-tetraphenyl-9,9′- spirobifluorene (spiro-quarterphenyl) and 2,2′, 7,7′-tetrakis(biphenyl-4-yl)-9,9-spirobifluorene (spiro-sexiphenyl) and its evolution upon doping with Li atoms or Na atoms have been studied by means of photoelectron spectroscopy. With lithium atoms as the dopant, two charges are stored on the same spiro branch in the form of bipolarons, for both spiro-quarterphenyl and spiro-sexiphenyl. In contrast, for doping with sodium atoms, the size of the counter ion makes it less energetically desirable to store two charges onto a single branch, and the charged species are polarons independent of the level of doping; this result is confirmed by optical absorption data.

Electronic structure of conjugated polymers and interfaces in polymer-based electronics

Electron emission, in resonance with soft X-ray absorption, appears to provide a measure of the dispersion of the highest occupied and the lowest, core-hole distorted, unoccupied pi-bands in poly(p-phenylenevinylene).