Photoemission Studies of Polythiophene and Polyphenyl Films Produced via Surface Polymerization by Ion-Assisted Deposition

Abstract

Conducting polymer films are grown by mass-selected, hyperthermal thiophene ions coincident on a surface with a thermal beam of organic monomers of either alpha-terthiophene (3T) or p-terphenyl (3P) neutrals. Mass spectrometry and X-ray photoelectron spectroscopy previously verified polymerization of both 3T and 3P by 200 eV C(4)H(4)S(+) during surface polymerization by ion-assisted deposition (SPIAD). The electronic structure of these films are probed here by ultraviolet photoelectron spectroscopy (UPS) and polarized near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and compared with similar spectra of evaporated films. The conducting polymer films formed by SPIAD display new valence band features resulting from a reduction in both their band gap and barrier to hole injection, which are calculated from the occupied and unoccupied valence band states measured by UPS and NEXAFS. These changes in film electronic structure result from an increase in the electron conjugation length and other changes in film structure induced by SPIAD.

Photoresponse of PbS nanoparticles–quaterthiophene films prepared by gaseous deposition as probed by XPS

“…Enhanced bonding in ion-assisted deposition of oligothiophenes has been observed previously [11][12][13] and was predicted by molecular dynamic simulations. 14 Ongoing work is exploring a similar mechanism in which the 4T þ PbS þ ion films display enhanced covalent bonding between the PbS nanoparticles and the 4T phase, induced by ion-assisted modification.…”

“…13 Thus, the C 1s peak was fit with a single component. Film and nanoparticle morphology was not directly examined here.…”

“…10 The acetylene ions used in ion-assisted deposition behave both as catalysts and reagents by energetically inducing bonding between condensed phase species and forming adducts with the neutral reagents. [11][12][13][14][15] X-ray photoelectron spectroscopy (XPS) was employed to probe photoconductivity of the PbS nanoparticle-4T composite films. For insulating and semiconducting samples, it has been observed that surface charging can shift the measured binding energies in an X-ray photoelectron (XP) spectrum.…”

(More) About biphenyl first excited triplet state energy

“…Biphenyl has a renewed significance today, since it is the repeating unit of polyphenyl films with potential application as conducting polymers [13,14] and as light emitting diodes [15,16]. The triplet energy of biphenyl tabulated in reference databases [17,18] is still its spectroscopic energy (E T (biphenyl) = 65.5 kcal mol −1 ).…”

Oligômeros e polímeros derivados do tiofeno: síntese e aplicações

“…Uma menor L e pode ser conseguida através do aumento da conjugação da estrutura polimérica ou dopante. 18 Uma das estratégias mais empregadas é a variação do padrão de substituição da cadeia lateral dos politiofenos, o que pode resultar na modulação planejada das propriedades eletrônicas do polímero, de modo a se obter compostos que, por exemplo, quando submetidos a um estí-mulo elétrico conduzam a várias colorações, indo do vermelho até o azul dependendo do substituinte no anel tiofênico. 2 Assim, pode-e constatar a grande importância do controle dos diferentes métodos Figura 1.…”