Experimental study of charge injection from gold/aluminium into regioregular poly (3-hexylthiophene)

Abstract

The nature of charge injection has been investigated across the gold (Au) / aluminium (Al) - regioregular poly(3-hexylthiophene), rrP3HT, interface as a function of channel length of the two electrodes. The sheet resistance (R_□(□)) of rrP3HT in contact with Au/Al electrodes and contact resistance (bottom contact and top contact) are also measured. Sheet resistance was found to be 8×〖10〗^8 Ω/□. The total resistance (R_t) increases from 12.5 to 33 MΩ as the channel length (L) increases between 20 and 80 µm at room temperature. The I-V characteristics of a Au (bottom)/P3HT/Au (top) sandwich cell and Al/P3HT/Al contacts are analyzed by using the Keithley source-measure unit for all samples separately and the hole barrier height at the top and bottom contacts has been estimated. I-V curve shows ohmic contact and nonohmic properties (nonlinear) of the Au/P3HT/Au and Al/P3HT/Al interfaces respectively.