Organic Light Emitting Diodes (OLEDs) are a cutting-edge lighting technology that allows to create thin, light weight, diffuse-emitting, glare-free, and even transparent light sources having low power consumption, wide color gamut, fast response time, and precise dimming. Transparent OLEDs (TrOLEDs) can be integrated into architectural glass windows, car windshields, divider panels, or lamps, thus enabling the creation of lighting objects with captivating and innovative designs, allowing natural light to pass through, since they are optically transparent when turned off. In order to achieve high-performance TrOLED, it is necessary to develop transparent electrodes with superior optical and electrical properties, to replace the opaque metal top electrodes that are commonly used in bottom-emitting OLEDs. Transparent conducting oxides (TCOs) are the most widely used transparent materials for bottom electrodes, and sputtering technology is the most common technique to deposit such materials. However, sputtering of high-quality TCO is not well suited for the fabrication of OLED top electrodes because it exposes the underlying organic layers to damages by the plasma emission of high-energy particles. In this study, the effects of sputter deposition of Indium Tin Oxide (ITO) on Tris(8-hydroxyquinoline) aluminum(III) (Alq₃) OLED active layer have been investigated, to establish the best compromise between process conditions and ITO films electro-optical properties to reduce the damage induced by sputtering. Moreover, the impact of introducing a thin thermally evaporated calcium (Ca) layer, before ITO sputtering, has also been examined. In this case, Ca acts both as a protective layer for the underlying Alq₃ and, at the same time, as a good electron injector for OLEDs.

Exciplex are generated at the heterojunction interface of electron donor and acceptor materials. Exciplex strategy can, thus, reduce molecular design difficulties for obtaining near-UV emission by selecting the appropriate electron donors and acceptors. Induced exciplex of Tris(4-carbazoyl-9-ylphenyl)amine (TCTA)/ 2,9-Dimethyl-4,7-diphenyl-1,10- phenanthroline (BCP) were applied to design deep blue organic light emitting diodes (OLEDs). BCP was used as an electron transport material and TCTA as a hole transporting material. The investigations carried out on planar-heterojunction have shown that recombination region was located at the vicinity of TCTA/BCP interface leading to exciplex formation. Furthermore, the thicknesses of BCP and TCTA layers play a key role in the control of the recombination zone and the emission color of the OLEDs. The electroluminescent spectra of planar-heterojunction exciplex-based OLEDs displayed deep blue emission at 423 nm with CIE coordinate of (0.16, 0.11). The emission of bulk-heterojunction exciplex-based OLEDs are also investigated showing that their emission is dominated by electroplex emission. The results demonstrate the feasibility of fabricating the efficient exciplex-based deep-blue OLED.

We have studied the local photobleaching in TDBC layers for grating and strong coupling applications. With this method, the refractive index can be both locally and spectrally modulated. In this work, photobleaching and fabricated micro-devices have been investigated highlighting the high potential of this interesting materials for photonics applications.

Organic materials are actively researched for their potential application in the manufacturing of solar cells. The possibility to vary the structure of the molecules and the possibility of using wet casting methods such as spin-coating or inkjet printing are the main advantages of these materials. In recent years the research has shifted away from fullerenes as electron acceptor materials due to their disadvantages. Additionally, the introduction of a third component in the active layer of organic solar cells allows the expansion of the absorption spectrum of the cell thus increasing the solar cell efficiency compared to the two-component bulk heterojunctions. The manufacturing of ternary organic solar cells (TOSC) is easier than tandem cells, thus reducing the potential costs upon their commercialization.

In this work, we have studied the application of novel dicyanomethylene-functionalized s-indacene-tetraone based non-fullerene acceptors IC-1 and IC-2 as the third component in TOSCs. The chromophores IC-1 and IC-2 with donor-acceptor-donor (D-A-D) molecular composition were acquired by condensation reactions between s-indacene-tetraone derivative acceptor fragment and aniline- or indoline-based electron-donating fragments. Electron donor polymer PM6 and electron acceptor material Y7 were used as the base materials for the TOSCs. The energy levels of IC-1 and IC-2 are located between the levels of PM6 and Y7 creating the cascade effect. IC-2 absorption has an additional shoulder between 650 nm and 800 nm which helps to increase the power conversion efficiency and reduce the losses shown by the external quantum efficiency (EQE) measurements.

A model for characterizing emission zone profiles (EMZ) in organic LEDs is introduced. Considering limits for resolving EMZ features yields a characterization by two parameters only. This enables to compare different EMZ results numerically and to define optimization targets that can be observed experimentally. Exemplary data on current-dependent EMZ shift illustrate the application of the method.

We report a numerical investigation of the recently proposed (Nature 621, 2023, 746) high-speed μ-OLED optically pumped organic laser and confirm that in this configuration the threshold for quasi-CW lasing is much easier reached than in case of a direct-electrically pumped organic laser diode. With a new model for the electrically biased OLED, we simulate the generation of pulsed and quasi-CW light. This light is fed into the organic laser where it optically pumps the emitting organic medium The model is voltage-driven and includes field-enhanced Langevin recombination in the OLED, Stoke-shifted reabsorption in both the OLED and organic laser, with an optical cavity in the latter. We numerically demonstrate 3.5 kA/cm² laser threshold current density, 1 GHz modulation and conjecture the capability of Gb/s data transmission with this device.

In this work, single layer 3,3′-Di(9H-carbazol-9-yl)-1,1′-biphenyl (mCBP), tris(4-carbazoyl-9-ylphenyl)amine (TCTA) and 4,6-Bis(3,5-di-3-pyridinylphenyl)-2-methylpyrimidine (B3PymPm) organic thin films optical properties were investigated by spectroscopic ellipsometry and spectrophotometer. Films were fabricated by thermal evaporation on glass, quartz, and indium tin oxide (ITO) substrates. The substrate impact on complex refractive index and absorption coefficient of thin films is evaluated and discussed.

Although the organic molecule dopamine (3,4-dihydroxyphenethylamine) is commonly known as the “hormone of happiness”, thin films of poly-dopamine also have interesting technical properties. When produced by dip coating, the self-organizing layers grow in a reproducible thickness of single or multiple molecule monolayers of a few nanometer thickness only. In this work, we introduce a method of determining the layer thickness of poly-dopamine on mirrors for astronomical X-ray telescopes. This work is based on spectroscopic ellipsometry measurements and involves the development of an optical model for the poly-dopamine layers including the dielectric function. Thereby the complex refractive index of the produced layers was determined, covering the range from the ultraviolet to the near infrared spectral region. These measurement results and the corresponding technical challenges are presented in this contribution. Furthermore, an outlook to potential technical applications of this interesting material is given and poly-dopamine layers will make scientist and engineers hopefully happy as an innovative and fascinating technical solution for the future.

Graphene quantum dots (GQDs) are one kind of carbon-based nanomaterials which can be used for numerous applications, such as energy conservation, luminescent solar concentrators, bioimaging, and biosensing. It has low toxicity, high conductivity and it shows exceptional optical properties, including photoluminescence (PL) emission which could be adjusted from blue to red emission depending on the solvent. Another interesting properties found in GQDs is anti-Stokes photoluminescence (ASPL). However, the mechanism of ASPL in GQDs was still unclear. In this study, GQDs were prepared with 1,3,6-trinitropyrene as the precursor, then dissolved in toluene (GQDs@TL). The results show that GQDs@TL has PL emission peak at ~595 nm when excited at ~530 nm and ~700 nm. It showed that GQDs@TL has large energy gain (~310 meV). To further understand the mechanism of ASPL, additional temperature-dependent measurements were done. We found that the large energy gain could be gained owing to the contribution of phonon energy and hot-band absorption energy (E_HBA) coming from molecular and lattice vibration. Therefore, this study will conclude the mechanism of ASPL.

A highly emissive blue organic light emitting diodes (OLED) for use as an algae excitation source in a biosensor was designed and optimized to meet spectral filtering requirements of the system. This source needs to exhibit high emission around 470-480 nm (algae absorption) combined with low emission in the algae fluorescence bandwidth (550-600 nm) in order to avoid any overlapping signal in the biosensor’s sensitivity range. To address these issues, a microcavity device (MOLED) was studied and optimized. In order to further decrease the residual parasitic emission in the green spectral range, an additional filter was also integrated in the device. An improvement in peak intensity of 2.7 times the reference value was obtained, as well as a significant reduction of the parasitic emission in the green range. These improvements in peak intensity and spectral filtering should lead to a suitable blue OLED excitation source for compact optical biosensors.