Channel semiconducting selenophenes

Selenophene-based FET materials had not been studied until 2003, when Kunugi et al. evaluated the semiconducting characteristics of quaterselenophene (11) [101], The hole mobility (3.6 x 10 cm s ) of 11 is comparable to that of quaterthiophene. This is in good agreement with the above description that doped oligoselenophenes have nearly the same conductivities as oligothiophenes. 

Although polythiophenes are best utilized as solution-processable high-performance p-type semiconductors [102], polyselenophenes are of no use as FET materials because of their insolubility. However, it was recently reported that selenophene-containing copolymers 47-50 could form thin films with a solution-processable method and showed p-channel FET responses with hole mobilities of the order of 10 -10 cm V s [103]. When the thin films were annealed after spin coating, the mobilities were enhanced by one order of magnitude. 

Recently, Kim et al. reported that a FET using the copolymer of fluorene and selenophene, poly(9,9 -dioctylfluorene-a/t-biselenophene) (51), as an active layer exhibited a high hole mobiUty of 0.012 cm V s which is better than the performance of the fluorene and thiophene copolymer counterpart [104]. It is speculated that the high mobility of 51 is a result of the close molecular packing and the well-defined orientation of selenophene-containing polymer chains. 

Compound HOMO (eV) LUMO (eV) HOMO-LUMO gap (eV) Mobility (cm V-i s-i) Stability in air 

Compound 53 is also a very stable organic semiconductor with a high hole mobility of 0.31 cm.  

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