A solution processable fluorene-benzothiadiazole small molecule for n-type organic field-effect transistors

We report an n-type organic semiconductor [2-({7-(9,9-di-n-propyl-9H-fluoren-2-yl}benzo[c][1,2,5] thiadiazol-4-yl) methylene]malononitrile (herein referred to as K12) for use in organic field-effect transistors (OFETs). K12 can be processed by spin-coating from solution or by vacuum deposition, organizing into highly orientated microcrystalline structures at modest (75 degrees C) annealing temperatures. OFETs with n-octyltrichlorosilane or hexamethyldisilazane monolayers, or poly(propylene-co-1-butene) (PPCB) modified dielectric surfaces were prepared. The mobility, ON/OFF ratio, threshold voltage, and current hysteresis were found to be dependent on the thermal history of the film and surface onto which it was deposited. The highest OFET mobility achieved was 2.4 X 10(-3) cm(2)/V s, for spin-coated films with a PPCB modified silicon dioxide dielectric. (C) 2011 American Institute of Physics. [doi:10.1063/1.3569818]