Top-emission Organic Light-emitting Device Research Articles

Stamped Self-Assembled Monolayers on Electrode for Connecting Organic Light-Emitting Diode and Organic Photovoltaic Device

The stamping process of self-assembled monolayers (SAMs) with polydimethylsiloxane (PDMS) mold on the Ag electrode was demonstrated, for use as the anode of a top-emission organic light-emitting device (OLED) and the cathode of an organic photovoltaic (OPV) device stacked underneath. Such SAMs reduce the barrier for hole injection from the Ag to the hole-transport layer of OLED. The PDMS mold coated with SAMs can be used repeatedly, for more than nine times. In this tandem device, the power conversation efficiency under OPV-mode operation and the current efficiency under OLED-mode operation were nearly identical to those in individual devices without compromise.

Improved Performance of Top-Emission Organic Light Emitting Device With a Mixed Single Layer

Top-emission organic light emitting devices (TEOLED) with a mixed single layer by mixing of electron transport materials, hole transport material and dope material were investigated. With an optimized mixing ratio of PyPySPyPy:Alq3:α-NPD:Rubrene [25:50:25:1], maximum power efficiency, 3.45 lm/W, and maximum luminance, 7,000 cd/m2 was obtained. Compared to the conventional heterostructure device, the performance was improved with a factor of more than two. The dependence of organic layer thickness on device performance was also investigated and the result showed that 100 nm was an appropriate thickness for good performance of mixed single layer TEOLED. In addition, the maximum luminance and power efficiency were obtained at 20,000 cd/m2 and 7.5 lm/W, respectively, when TPD layer of 45 nm was capped onto top metal electrode.

Inverted top-emission organic light-emitting device with n-type silicon as cathode

Top-emission organic light-emitting devices (OLEDs) with configuration of n-Si (cathode)/Au : Sb 2 nm/Sm 4 nm/AlQ 60 nm/NPB 60 nm/V2O5 10 nm/Au 7 nm (anode) are reported on. We have found that high surface electron concentration and surface modification of n-Si are beneficial to the electron injection. The power efficiency of a device with a 10−3 Ω cm n-Si/Au : Sb cathode is 10 times more than that of a device with a 10 Ω cm n-Si/Au cathode. With an optimized thickness of V2O5, such a device exhibits much higher electroluminescence efficiency (0.8 lm W−1) than the conventional top-emission OLEDs with p-Si or n-Si anodes reported on previously (0.2 lm W−1).

Red electrophosphorescent top emission organic light-emitting device with Ca∕Ag semitransparent cathode

Using a Ca (10nm)∕Ag (10nm) semitransparent cathode and efficient electron transport and/or buffer layer, red electrophosphorescent top emission organic light-emitting device has been fabricated. A low turn-on voltage of 4.6V and clean electrophosphorence peaks at 616 and 674nm are reported. X-ray photoelectron spectroscopy depth profiling measurements reveal the presence of Ca(OH)2 in Ca∕Ag bilayer cathode and the skin depth over 15nm in the visible region is determined in this structure. Results show that the compositional modification of the Ca∕Ag cathode enhances its optical transparency and final performance of the electrophosphorescent top emission device.

Scanning photoelectron microscopic study of top-emission organic light-emitting device degradation under high-bias voltage

The degradation process of a top-emission organic light-emitting device (TOLED) under high-bias voltage was investigated using a scanning photoelectron microscope (SPEM). The TOLED was in situ biased to reveal the degraded area inside the SPEM chamber. The SPEM data showed a volcano-type structure inside the degraded area. The overall results of the spectroscopic analysis suggest that strong degradation was accompanied by an eruption underneath the cathode layer. It is posited that the hot gases from the erupted area separated the cathode layer from the organic layer, forming a large bubble, and that, as the bubble exploded, the pressure of the gas blew away the cathode layer.

Failure of the top emission organic light-emitting device with a Ca/Ag semitransparent cathode

The influence of vacuum conditions during the deposition of Ca/Ag cathode on the performance of top emission organic light-emitting devices (TEOLEDs) is investigated. The fabricated devices have been characterized by current–voltage ( I– V) and electroluminescence (EL) measurements. Low turn-on voltage and high yield of EL are observed if the cathode is deposited in a better background pressure than 2.78 × 10 −6 Torr, whereas the deposition of cathode in a poor back ground pressure (<2.78 × 10 −6 Torr) leads to device failure. It is argued that the partial oxidation of Ca significantly improves the transparency of the Ca/Ag cathode while remaining conducting, whereas the complete oxidation of Ca (formation of Ca O bonds) results into device failure.

Realization of an efficient top emission organic light-emitting device with novel electrodes

Top emission organic light-emitting devices (TEOLEDs) have generated a considerable interest owing to their use in the development of active matrix displays. Requirements for the next-generation displays, which are high-quality video images, lightweight and thin, and low power consumption can be realized in TEOLEDs. The Ni/4,4-bis[ N-(1-naphtyl)- N-phenyl-amino]biphenyl(α-NPD)/Alq 3/2,9-dimethyl-4,7 diphenyl-1,10-phenanthroline (BCP)/Ca/Ag top emitting device has been fabricated. The reflective Ni anode and Ca/Ag semitransparent double layer cathode have been characterized. Suitable explanation is proposed for the high transmittance of Ca/Ag structure.

Realization of an efficient top emission organic light-emitting device with novel electrodes

Top emission organic light-emitting devices (TEOLEDs) have generated a considerable interest owing to their use in the development of active matrix displays. Requirements for the next-generation displays, which are high-quality video images, lightweight and thin, and low power consumption can be realized in TEOLEDs. The Ni/4,4-bis[N-(1-naphtyl)-N-phenyl-amino]biphenyl(α-NPD)/Alq3/2,9-dimethyl-4,7 diphenyl-1,10-phenanthroline (BCP)/Ca/Ag top emitting device has been fabricated. The reflective Ni anode and Ca/Ag semitransparent double layer cathode have been characterized. Suitable explanation is proposed for the high transmittance of Ca/Ag structure.