Electrical Characterization of Polyfluorene-Based Metal-Insulator-Semiconductor Diodes

Abstract

ABSTRACTPolyfluorenes (PFs) have emerged as a promising family of blue polymer light-emitting diodes (PLED) due to their high electroluminescence quantum yield. Metal-insulator-semiconductor (MIS) diodes are the two terminal analogues of thin film transistors sharing the same basic layer structure. We have investigated two different structures based on poly [9,9'-(di 2-ethylhexyl)fluorene] (PF2/6), a MIS diode and a hole-only PLED. The MIS diodes were fabricated with the PF2/6 layer on p+ Si /Al2O3 substrates, and were characterized by means of capacitance-voltage (C-V) measurements as a function of frequency. From C-V measurements, the unintentional doping density is evaluated as ∼5.7×1017 cm−3 at frequencies above 20 kHz. The interface trap density is estimated as ∼7.2×1011 eV−1cm−2 at 10 kHz. Current-voltage measurements of PF2/6-based PLEDs shows a shallow trap space-charge-limited conduction from which the energy of the traps and hole mobilities are estimated.