Direct Photoalignment and Optical Patterning of Molecular Thin Films

Abstract

A novel strategy for direct photoalignment of molecular materials using optothermal re-orientation is introduced. Photoalignment for molecular materials such as the organic semiconductor tetracene is shown, without relying on additional photoreactive dopants or alignment layers. Patterning and polarized light emission, e.g., for polarized organic light emitting diodes is demonstrated.

Tetracene Ultrathin Film Growth on Hydrogen-Passivated Silicon

“…However, from NEXAFS alone it is not clear if the molecules are oriented with the molecular long axis (LA) closer to be parallel to the underlying surface or perpendicular to it (see Figure ). From all reports in the literature (utilizing XRD, LEED, and AFM) ,,,,,,, as well as our own total energy calculations, we can safely assume an upright-standing Tc orientation.…”

“…Tc structure formation has been widely studied on several different weakly interacting surfaces, including H–Si, ,,− Si oxide, ,,− AlO x /Ni 3 Al­(111), − polystyrene, parylene C, poly­(methyl methacrylate), hexamethyl­disilazane, Mylar, evaporated carbon, and highly oriented pyrolytic graphite . Thanks to the weak coupling to the substrates, the results are largely transferable.…”

Impact of anisotropic interactions on nonequilibrium cluster growth at surfaces

“…Several aspects from the sub-monolayer to the multilayer growth regime have been experimentally investigated in detail by atomic force microscopy [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], scanning tunneling microscopy [19][20][21][22], high or low energy electron diffraction [23][24][25][26][27][28][29], Raman [30] and Auger electron spectroscopy [31] experiments. Recently, also X-ray scattering studies of epitaxially grown thin films have been performed [32][33][34][36][37][38][39][40]. Furthermore, such purely inorganic systems are theoretically well studied by means of rate equation approaches [47][48][49][50][51][52][53][54][55][56]<...>…”

“…Indeed, depending on properties of initially nucleated clusters, the morphology of the grown structure can drastically vary in the multilayer regime. This may strongly affect mechanical, optical and electrical properties of thin film devices [34,40].…”

“…This is even more the case for systems of conjugated organic molecules (COM). In contrast to most atomic systems or systems of nearly spherical organic molecules like fullerene C 60 , elongated organic molecules like diindenoperylene, p-sexyphenyl (6P), the perylene derivative PTCDI-C 8 or pentacene are known to generally in-teract anisotropically with each other when adsorbed on both, organic and inorganic substrates [34,37,39,40,[66][67][68][69][70][71]. Therefore one expects rather complex cluster shapes and corresponding changes in the cluster density, cluster size distribution and the coalescence behavior in the sub-monolayer growth regime as compared to atomic systems.…”