Improvement of electrical and optical characteristics of the organic light-emitting diodes with F-SAM ultra thin hole-injection layer

Abstract

Organic light-emitting diodes (OLEDs) emits light depending on the ratio of recombination charge carrier. However it has problem that hole and electron mobility is different in the OLEDs. It is affects the device efficiency. This difference can bring about a Space-Charge-Limited Current (SCLC) and give rise to a low efficiency of luminance and driving voltage. This is due to an imbalance between the numbers of charge carriers, which reduces a recombination efficiency. To increase of OLEDs performance efficiency, need to improve charge carrier mobility. These matters can be relieved by using a substance which reduces an energy-barrier height between the thin organic film and charge transport layer. This experiment was conducted using (Heptadecafluoro-1, 1, 2, 2-Tetrahydrodecyl)-1-Triethoxysilane (F-SAM) as a thin Hole-Injection Layer (HIL) without physical defects through hydrolysis to the surface on the Indium-Tin-Oxide (ITO) substrate. To evaluation the emission characteristics and optics of the device using the thin-film F-SAM as HIL, a device structure of ITO (180 nm)/(F-SAM)/TPD (40 nm)/Alq3 (60 nm)/Liq (2 nm)/Al (100 nm) was prepared. For the efficient injection of holes, F-SAM materials having high electric dipole moment were used. It was proved that there is an improvement of efficiency of the OLEDs, possibly due to a balance of number of charge carriers. For this reason, by reducing the difference in carrier mobility is affected to increase the efficiency of the OLEDs.