White phosphorescent organic light emitting diodes (WOLEDs) offer many advantages for solid-state lighting applications, including high color-rendering indexes, tunable color temperatures, and color stability. In side-by-side geometry, emissive stripes of different colors can be driven separately to enable color tunability. Previous side-by-side OLEDs have been patterned using shadow masks or chemical lift-off methods. We utilize a photolithographic peel-off patterning method to fabricate side-by-side WOLEDs consisting of two isolated color stripes, one emitting in the yellow and the other in the blue. This method allows for high-resolution stripe patterning without sacrificing device performance and lifetime.

The efficiency of organic light emitting diodes has been significantly improved during the last several years by developing phosphorescent and TADF emitters with high horizontal emitting dipole orientation and high PLQY along with the development of device structure with excellent charge balance to get EQE reaching almost 40%, corresponding to almost the theoretical limit of the efficiency. The most important remaining issue now is the development of stable deep blue OLEDs. In this talk, we will firstly present a theoretical approach to understand the degradation process of phosphorescent OLEDs followed by the three strategies to realize deep blue OLEDs including the phosphorescent dye sensitized fluorescent OLEDs, deep blue TADF OLEDs using emitters with narrow emission spectrum, high PLQY and horizontal emitting dipole orientation, and finally deep blue OLEDs utilizing triplet-triplet annihilation (TTA) process based on anthracene derivatives with the efficiencies overcoming the conventional theoretical limit.

The functional layer encompasses ~15 nm thick Zinc Oxide nanoparticles (ZnO NPs) in a polyethylenimine ethoxylated (PEIE) matrix. PEIE acts as a surface modifier on ZnO NPs and also interlinks the individual ZnO NPs resulting in enhanced electron injection and transport. Owing to the deep valence band energy state of the ZnO NPs, the hole mobility is reduced significantly. The optimized light outcoupling in the OLED using the functional layer is achieved with the combination of optical light outcoupling simulation and thickness optimization by spin coating. The outcome of these optimizations is a solution processable high efficient, low-cost OLED.

Exciton distribution in white OLEDs (WOLEDs) with broad emission zones containing multiple material interfaces are difficult to accurately predict, making their optimal design accessible only through the fabrication and measurement of numerous iterations involving different materials and layer thicknesses. We present a comprehensive model that is suitable for predicting the exciton distribution in state-of-art WOLEDs. The model captures both charge and exciton dynamics and takes all structural components of complex WOLEDs into consideration, including more than three interface barriers and emission layers with multiple dopants. The model quantitatively reproduces the measured exciton profile and suggests a charge blocking layer reduces the intensity-dependent color shifts in WOLEDs. The emission of WOLEDs with and without blocking layers are measured, and matches the calculated exciton distribution.

Nanometer-thick, ultrathin coatings applied over a large area are of paramount importance for various application fields such as biomedicine, space and automotive, organic electronics, memory devices, or energy storage devices. So far wet chemical deposition as a cost-effective, scalable, and versatile method can only be used for thicker deposits, at least 30nm in thickness. In this work, the formation of uniform ultra-thin coatings with thicknesses below 15nm using a nature-inspired, roll-to-roll compatible Spray-on-Screen (SoS) technology is reported. For this, the finite micro-droplet generation of Ultrasonic Spray Coating (USSC) is combined with the coating formation from a screen printing mesh. Hydrophobic micro-threads of the mesh, resembling the micro-hair on the legs of water striders, produce millidroplets from micro droplets, and when applying an external pressure to the mesh, dynamic wetting is enforced. OLEDs are build using this Spray-on-Screen technology.

A thin layer of NaCl with a thickness of "~ 3 nm" was deposited on 15 nm ZnO NP+PEIE/ 80 nm SY in an OLED stack. A super thin layer of NaCl acts as a surface modifier increasing the electron injection, current density, external quantum efficiency and finally the overall performance of the OLED. The optical, electrical and morphological properties of OLEDs are enhanced by both solution-processed and vacuum-processed NaCl deposition. Significant enhancement in the EQE and illuminance of the NaCl-based device were exhibited compared with standard devices and are allowed to use because of their abundant availability and nontoxicity for efficient OLEDs.

Cyclometalated iridium complexes are a specific class of transition metal chromophores (TMCs) widely employed as phosphors in organic light emitting diodes (OLEDs), as photoredox catalysts, and increasingly as non-linear optical (NLO) materials. This research investigated the effect of derivatization on the parent complex [Ir(pbt)2(acac)], where pbt is 2-phenylbenzothiazole and acac is acetylacetonate. Specifically, hole transport groups, either triphenylamines or carbazoles, were installed at different positions along the pbt ligand framework. The chemical syntheses, electrochemistry, and photophysics of these complexes will be discussed in detail with reference to our previous work and the parent complex.

The preparation of 3D composite structures incorporating either molecular entities and/or functional nanoparticles represents a challenge on the way to optical devices. The preparation of monolithic transparent silica-based material using the sol-gel process and incorporation of functional nanostructures (plasmonic, luminescent) will be presented here. The sol-gel process allows the design of transparent hybrid monolithic xerogels or aerogels. Plasmonic or luminescent nanostructures can be introduced during the process. Plasmonic nanostructures are functionalized in order to allow their homogeneous incorporation in the transparent hybrid silica matrices. Co-dispersion of the metallic structures with dyes can be achieved. The role of the concentration, shape and size of the metal nanoparticles on the nonlinear optical response is crucial, both in the visible and in the NIR. Similarly, chiral nanoparticles can be introduced to provide chiral properties to the final glass.

In this work we will review our activities on the realization of systems and networks of light-emitting nanofibers with complex topologies. The optical gain and lasing emission properties can be controlled in such systems through the concentration of the chromophores and the optical pumping features. The research leading to these results has received funding from the Italian Minister of University and Research through the PRIN 201795SBA3 and 2017PHRM8X projects.

Electrospun nonwoven mats are currently being developed for applications in different research fields. By changing materials, processing conditions and assembly architecture of the fibers, textiles with an enormous variety of functionalities can be generated. Here we report on two classes of materials, based on piezo-responsive polymers for mechanical energy harvesting and on SU-8 resins for time-temperature indicators, respectively. This research has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 682157, “xPRINT”) and the Italian Minister of University and Research (PRIN 2017PHRM8X and 20173L7W8K).

The main objective of this project is to develop nonlinearly absorbing hybrid devices at 1550 nm. This optical range is particulary interesting while it is widely used for optics fibers, it is safe for the human eye and the atmosphere is completely transparent. In this context, we designed aza-BODIPY due to their particular photophysical properties, characterized by a high extinction coefficient and a fluorescence in the NIR region.[1] Although these dyes are mainly used as fluorescent probes for bio imaging [2] or in active layer for organic photovoltaic,[3] recent studies in our group showed their high potential for nonlinear applications, where their enhanced two-photon efficiency and excited state absorption in the wavelength of interest have been demonstrated.[1] These new aza-BODIPY derivatives with different donor units in order to increase the charge transfer properties led to improve the final efficiency of hybrid devices. [4] Finally, we will discuss the use of plasmonic nanoparticles to strongly enhance the nonlinear performance of these dyes within hybrid systems, creating a synergy effect never observed on such a system in the NIR region.[5] References 1. S. Pascal, Q. Bellier, S. David, P.-A. Bouit, S.-H. Chi, N. S. Makarov, B. Le Guennic, S. Chibani, G. Berginc, P. Feneyrou, D. Jacquemin, J. W. Perry, O. Maury, C. Andraud, J. Phys. Chem. C, (123): 23661, 2019. 2. Z. Shi, X. Han, W. Hu, H. Bai, B. Peng, L. Ji, Q. Fan, L. Li, W. Huang, Chem. Soc. Rev., (49): 7533, 2020. 3. R. S. Rao, B. Yadagiri, G. D. Sharma, S. P. Singh, Chem. Commun., (55) : 12535, 2019. 4. S. David, D. Chateau, H.-J. Chang, L. H. Karlsson, M. V. Bondar, C. Lopes, B. Le Guennic, D. Jacquemin, G. Berginc, O. Maury, S. Parola, C. Andraud J. Phys. Chem. C, (124): 24344, 2020. 5. D. Château, S. David, G. Berginc, C. Lopes, F. Chaput, F. Lerouge, A. Désert, C. Andraud, S. Parola ACS Appl. Nano Mater., (5): 3773, 2022. Acknowledgments: we are grateful to DGA for PRO-IR project support

We report on our ongoing activities on photonics elements made through additive manufacturing technologies. We discuss how the vat-photopolimerization processes can be monitored in-situ through optical methods. We also introduce novel optical components with 3D surface reliefs that generate complex light patterns tailorable by uniaxial strain. The research leading to these results has received funding the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 682157, “xPRINT”) and from the Italian Minister of University and Research through the PRIN 2017PHRM8X project.

Among the different types of opto-electric transmitter devices, the high-efficient electro-optic (EO) waveguides have recently received intense research highlights due to the invention of achievable 100 Gbaud and beyond signaling with the extremely reduced power consumption. Our strong Pockels effect waveguides offer important advantages such as a large EO coefficient (n^3r33>1000 pm/V), broadband response, and excellent compatibility with other materials and silicon photonic devices. Low device manufacturing costs and high yield are excellent advantages for industrial solutions for mass production of assembled optical transceivers.

This conference poster presentation was prepared for the Photonics West OPTO 2023 Symposium.