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1091-AA07-64

Low Mass Organic Semiconductor-polymer Dielectric Nanocomposites: Influence of the Guest-host Interactions on the OTFT Characteristics Marie-Beatrice Madec, David J Crouch, Gonzalo Rincon-LLorente, and Stephen G Yeates School of chemistry, Organic Materials Innovation Centre, OMIC-school of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom ABSTRACT. The morphology and organic field effect transistor (OFETs) properties of two component blends of semicrystalline 6,13-bis(triisopropylsilylethinyl)pentacene (TIPS-pentacene) with selected amorphous and semi-crystalline low permittivity side chain aromatic insulating binders deposited at room temperature under vacuum from a good solvent are reported. When blended with an amorphous binder there is evidence from XPS for strong interaction between TIPSpentacene and binder in the solidified film giving rise to twisted TIPS-pentacene crystals containing dislocations. Due to this strong interaction we see no evidence of segregation of TIPS-pentacene towards the active interface and hence we observe a rapid fall off in saturated hole mobility at a active concentration less than 50 wt-%. When blended with a crystalline binder there is no evidence from XPS of any interaction between TIPS-pentacene and binder in the solidified film. We propose that when a crystalline binder is used, which crystallizes more slowly from solution than TIPS-pentacene, we observe stratification of the active material to both interfaces and as a result an increase of saturated hole mobility to 0.4 cm2/Vs at 20 wt-% in isotactic poly(vinylbisphenyl). The potential application of the approach are in the formulation of low cost organic semiconductors whose solution and solid state properties can be fine tuned by careful binder selection.

INTRODUCTION. OTFTs based on pentacene exhibit the best performance to date with field effect mobilities of 3 cm2 V-1 s-1 for vacuum deposited and 7 cm2 V-1 s-1 for single crystal devices, respectively. [1]. 6,13 substituted pentacene’s have been the subject of intensive recent investigation attempting to combine good low cost solution processability with high performance. The performance to date of such materials when solution processed in single discrete devices is good but is however limited by the inability to precisely control their crystallization behaviour over large areas. Here we compare the two component blending of semicrystalline [6,13-bis(triisopropylsilylethynyl) pentacene] [2] TIPS-pentacene with selected amorphous and semi-crystalline low permittivity insulating polymer binders deposited from a good solvent at room temperature and dried under vacuum. We show that for crystalline crystalline blends, processed at room temperature, crystallization induced phase separation of the two components occurs [3] during which the semiconductor is predominantly expelled to the surfaces of the cast film.

EXPERIMENTAL. 1,2,3,4-tetrahydronaphthalene (tetralin, anhydrous 99%), poly(α-methylstyrene) (PAMS), amorphous polyst