Stage structure in cesium doped pentacene

Structure and magnetic property of potassium intercalated pentacene: observation of superconducting phase in KxC22H14

“…In particular, the band dispersions are enhanced in phase H, that is, both valence and conduction band are widened in the herringbone plane [32]. While doping alkali-metals in low concentrations results in an increase of intermolecular distances of penta-cene, no structural phase transition was observed [33,34]. The structural transition from triclinic to monoclinic struc-ture, reported in this work, was induced by a further increase of the metal concentration.…”

Evidence for the formation of a Mott state in potassium-intercalated pentacene

“…The most striking aspect of our observations, namely, a sharp decrease in the conductivity starting at a carrier concentration of one electron per molecule concomitant with the re-entrance into an insulating state, has not been reported in earlier experiments on intercalated pentacene ͑in which the density of intercalants could not be determined [14][15][16][17][18] ͒ or in studies of pentacene field-effect transistors with gate electrolytes ͑in which a metallic state has not been observed 23 ͒. It implies that, contrary to the case of pentacene devices used in plastic electronics, the electronic properties of pentacene films at high carrier density cannot be described in terms of noninteracting electrons.…”

“…It is also known that intercalation is accompanied by a considerable expansion of the unit-cell c axis ͑by an amount close to the radii of the intercalated ions͒ while the in-plane lattice parameters a and b are only minorly affected. 15,16 A reliable estimate of the length of the expanded c axis is given by the sum of the radius of the alkali ion and the pristine c-axis parameter: the c-axis lattice constants that are obtained in this way for, e.g., RbPEN and CsPEN are within 2% of the experimental values. For K 1 PEN we construct the lattice parameters starting from two different polymorphs ͑one with c = 14.33 Å and the other with 14.53 Å͒ using a K + ionic radius of 1.33 Å.…”

“…Similar to the case of intercalated C 60 , 10 the alkali atoms donate their electrons to the lowest unoccupied molecular orbital ͑LUMO͒ of the pentacene molecules, whereas the iodine donate holes to the highest occupied molecular orbital ͑HOMO͒, enabling the control of the conductivity of the films. Earlier studies [11][12][13][14][15][16][17][18] indicate that upon iodine or rubidium intercalation the conductivity of pentacene films can become large ͑in the order of 100 S/cm͒ and exhibit a metallic temperature dependence. The experiments so far, however, have not led to an understanding of the doping dependence of the conductivity ͑e.g., how many electrons can be transferred upon intercalation͒ or of the microscopic nature of electrical conduction of doped pentacene in the high carrier density regime.…”

Analysis of metal-oxide-based charge generation layers used in stacked organic light-emitting diodes

“…We conclude that both the existence of MoO 3 with the optimized thickness and the heavily doped BCP layer ensure a very thin depletion layer that allows for efficient electron injection. 30 Since the tunneling probability is an exponential function of tunneling distance, the 100-Å-thick MoO 3 sample results in the highest tunneling injection efficiency compared to the other thicknesses used.…”