Electron spin resonance observation of gate-induced ambipolar charge carriers in organic devices

Abstract

Electron spin resonance (ESR) measurements are performed on gate-induced ambipolar charge carriers in composites of regioregular poly(3-hexylthiophne) (RR-P3HT) and Ceo using metal-insulator-semiconductor (MIS) diode structures with the RR-P3HT-C60 composite as the active semiconductor and Al2O3 as the gate insulator. Clear ESR signals of g ≈ 2.002 and g ≈ 1.998 are successfully observed for negative and positive gate voltages (VG), respectively, and they monotonically increase as |VG| increases in each accumulation mode. We demonstrate microscopically that positive and negative charge carriers with the signals g ≈ 2.002 and g ≈ 1.998 are ascribable to RR-P3HT and C60, respectively. © 2007 The Japan Society of Applied Physics.