Ionic liquid modified zinc oxide injection layer for inverted organic light-emitting diodes

Abstract We have demonstrated a novel approach for fabricating efficient hybrid organic–inorganic light emitting diodes (HyLEDs) by introducing dopants into solutions processable metal oxides as an interfacial layer. The doped ZnO is prepared by adding ionic liquid (IL) to a precursor solution for the ZnO. In this way a heavily doped ZnO:ILs cathode was obtained that enhances the electron injection properties and assures a good wetting of the organic active materials.

Ionically Assisted Charge Injection in Hybrid Organic−Inorganic Light-Emitting Diodes

We have developed hybrid organic−inorganic light-emitting diodes (HyLEDs) featuring a buffer layer of a conjugated polyelectrolyte (CPE) sandwiched between a light emitting polymer (LEP) film and a ZnO electron injection layer. Efficacies exceeding 5 cd/A and the possibility of employing various LEPs are demonstrated. These improvements, compared to HyLEDs without any interlayer, are attributed to the redistribution of ions in the CPE film, causing hole accumulation at the CPE/LEP interfaces and enhanced electron injection from the ZnO into the electroluminescent polymer. The intrinsic air-stability of the electrodes used in HyLEDs, together with the solution processability of the ZnO/CPE/L…

Hybrid organic-inorganic Light Emitting Diodes

Hybrid organic inorganic light emitting diodes are nowadays attracting great attention due to their intrinsic air stability and solution processability, which could result in low-cost, large area, light emitting devices. Despite the fact that high luminance values have been already demonstrated in recent publications, the efficiency of HyLEDs has been limited by its peculiar hole-dominated electronic mechanism. In particular, the electron injection is promoted by the hole accumulation at the metal oxide EIL/organic interface, but at the same time this mechanism leads to limits the device efficiency. It is known from the research in OLEDs that when the recombination zone is close to an inter…

SiPMs coated with TPB: coating protocol and characterization for NEXT

[EN] Silicon photomultipliers (SiPM) are the photon detectors chosen for the tracking readout in NEXT, a neutrinoless \bb decay experiment which uses a high pressure gaseous xenon time projection chamber (TPC). The reconstruction of event track and topology in this gaseous detector is a key handle for background rejection. Among the commercially available sensors that can be used for tracking, SiPMs offer important advantages, mainly high gain, ruggedness, cost-effectiveness and radio-purity. Their main drawback, however, is their non sensitivity in the emission spectrum of the xenon scintillation (peak at 175 nm). This is overcome by coating these sensors with the organic wavelength shifte…

Nucleant layer effect on nanocolumnar ZnO films grown by electrodeposition

Different ZnO nanostructured films were electrochemically grown, using an aqueous solution based on ZnCl2, on three types of transparent conductive oxides grow on commercial ITO (In2O3:Sn)-covered glass substrates: (1) ZnO prepared by spin coating, (2) ZnO prepared by direct current magnetron sputtering, and (3) commercial ITO-covered glass substrates. Although thin, these primary oxide layers play an important role on the properties of the nanostructured films grown on top of them. Additionally, these primary oxide layers prevent direct hole combination when used in optoelectronic devices. Structural and optical characterizations were carried out by scanning electron microscopy, atomic for…

Influence of the cyanine counter anions on a bi-layer solar cell performance

ABSTRACTWe present normal and inverted solution processed bi-layer solar cells using cationic cyanine dyes as the electron donor and a fullerene as the electron acceptor. The cells exhibit high open circuit voltages up to 1 volt showing the optimal alignment of donor and acceptor energy levels. We demonstrate the large effect that cyanine dye counter ions can have on the energetics of the solar cells and how the S-shaped current density vs. voltage (J-V) curves can be avoided.

Phosphorescent hybrid organic-inorganic light-emitting diodes.

Zinc oxide nanocrystals as electron injecting building blocks for plastic light sources

Hybrid inorganic–organic light emitting devices (HyLEDs) employing ZnO nanocrystals as one of their metal oxide contacts lead to very bright devices on plastic substrates with performances superior to those obtained from the rigid counterparts employing planar films of bulk ZnO. The superior performance is related to the increase in the bandgap of the ZnO nanocrystals caused by quantum confinement effects. We demonstrate that this effect diminishes with increasing annealing temperature of the ZnO nanocrystal layer due to a gradual decrease of the bandgap towards the bulk ZnO value. Therefore, best performances were obtained with room temperature processing of the ZnO nanocrystals.

Efficient, Cyanine Dye Based Bilayer Solar Cells

Simple bilayer solar cells, using commercially available cationic cyanine dyes as donors and evaporated C60 layer as an acceptor are prepared. Cyanine dyes with absorption maxima of 578, 615 and 697 nm having either perchlorate or hexafluorophosphate counter-ions are evaluated. The perchlorate dye leads to cells with S-shape current-voltage curves; only the dyes with the hexafluorophosphate counter-ions lead to efficient solar cells. When the wide bandgap dyes are employed, S-shape current-voltage curves are obtained when the conductive polymer PEDOT:PSS is used as hole transport layer. Substitution of PEDOT:PSS with MoO3 leads to cells with more rectangular current–voltage curves and high …

Meniscus coated high open-circuit voltage bi-layer solar cells

Neat bi-layer solar cells of a fullerene acceptor and a cyanine dye donor were prepared using meniscus coating. Meniscus coating is very material efficient and leads to high quality pinhole-free films. The cells exhibit high open circuit voltages of 1 volt, only 0.8 eV below the band gap of the cyanine dye. This is one of the smallest differences reported for organic solar cells and illustrates an almost optimal donor-acceptor energy level alignment.

Hybrid organic-inorganic light emitting diodes: effect of the metal oxide

Hybrid organic-inorganic light emitting diodes (HyLEDs), employing metal oxides as the electron injecting contacts, are interesting as an alternative to OLEDs. Until recently, the metal oxide of choice was either titanium dioxide or zinc oxide. In this work two wide bandgap metal oxides, HfO2 and MgO, are employed as electron injecting layer in HyLEDs. It is demonstrated that both the current density and the luminance values obtained are directly related to the barriers for electron injection (from the ITO to the metal oxide) and for hole transfer to the same metal oxide, outlining a new design rule for the optimization of HyLEDs. Record device efficacies (3.3 cd/A, >10000 cd/m2) using the …