We have studied alkyl-substituted pentacene derivatives for
solution-processing. By incorporation of substituent(s),
enhancement of solubility depending on substituted position(s) and substituent(s) was confirmed. Solution-processed
films of the derivatives showed highly oriented crystals with herringbone structure. This indicates that molecular
aggregation and electronic structure have been preserved after the substitution as expected from molecular design. Thinfilm
transistors of the derivatives exhibited large carrier mobility above 1cm2/Vs.
Solution-processed pentacene thin films could be prepared directly from pentacene solution without using precursor molecules. The solution-processed pentacene films showed highly oriented and highly crystalline structure. It appeared that large crystal-like platelets grown in the films, and it was assumed that crystalline size of solution-processed films was larger than that of sublimed films determined by in grazing incidence X-ray diffraction method and powder X-ray diffraction method. FETs formed with solution-processed films exhibited good switching properties with the mobility of 0.8cm2/Vs and on/off ratio above 105. Maximum carrier mobility above 1cm2/Vs was confirmed. The solution-processed film transistors showed lower threshold voltage due to lower carrier density in the films compared with sublimed films. It was confirmed that the solution-processed transistors showed more stable properties for the storage for months than sublimed film transistors. These aspects of transistor performance could be explained by structural difference between solution-processed and sublimed films. Transistors of solution-processed films of pentacene were fabricated by printing technique using a temperature controllable dispenser and the switching operations of isolated transistors were confirmed.