Kamijo, T., van Breemen, A.J.J.M., Ma, X. et al. A touchless user interface based on a near-infrared-sensitive transparent optical imager. Nat Electron (2023).

https://doi.org/10.1038/s41928-023-00970-8

Researchers have developed a touchless user interface based on a visually transparent near-infrared-sensitive organic photodetector (OPD) array. The touchless interface can be used on top of a display, eliminating the need for physical contact.

The OPD array is designed with optical transparency in mind, using printed copper grids and patterned organic photodetector subpixels. The design optimization results in a high photodetectivity of 10^12 Jones at 850 nm and a visible-light transmittance of 70%.

The touchless user interface can be used with a penlight or through gesture recognition, providing a hygienic and convenient alternative to traditional touch screens. The technology has potential applications in automated teller machines (ATMs), ticket vending machines, and kiosks, where hygiene is a concern. It is a scalable and flexible solution that can be integrated into a variety of display applications without size limitations or calibration requirements. 2D FEM simulations for the surface potential and the current density distributions derived from the printed Cu grid structure .

How Fluxim’s Research Tools were used

Setfos

Numerical electro-optical simulations for the photogenerated J–V curves of our NIR-sensitive OPDs were performed by using Setfos.

The VLT of the parallel OPD subpixel array was calculated by the summation of the simulated optical transmittance for each component using Setfos

Laoss

2D FEM simulations for the surface potential and the current density distributions derived from the printed Cu grid structure for our NIR-sensitive OPDs were performed by Laoss 4.0

Park, Y., Lee, G.S., Lee, W. et al.

Sci Rep 13, 1369 (2023).

https://doi.org/10.1038/s41598-023-27487-6

Researchers have designed Ir(III)-based heteroleptic NIR materials for near-infrared organic light-emitting diodes (NIR OLEDs) with a focus on radiance capacity (RC) rather than just radiance. The emitters exhibit a highly oriented horizontal dipole ratio, short radiative lifetime, and extremely low turn-on voltage.

The device demonstrates a high RC of 720 mW/sr/m2/V, making it a standout performer among Ir(III)-based NIR OLEDs with similar emission peaks, and has potential applications in healthcare, authentication, and night vision displays.

Measurement of the angle dependent p‑polarized photoluminescent spectrum (ADPL). The emission layer was deposited on a bare 50 nm-thick glass substrate. Then, glass encapsulation was done in a nitrogen ( N2)-filled glove box to avoid degradation from the air. A full angle dependent p-polarized PL spectrum was obtained with the goniometer based motorized intensity measurement system Phelos.

Lee, J. H., Huang, J.-X., Chen, C.-H., Lee, Y.-T., Chan, C.-Y., Dzeng, Y.-C., Tang, P.-W., Chen, C., Adachi, C., Chiu, T.-L., Lee, J.-H., Chen, C.-T.,

Adv. Optical Mater. 2023, 2202666.

https://doi.org/10.1002/adom.202202666

Researchers have designed and synthesized a novel near-ultraviolet (NUV) fluorescent material, BB4Ph, based on the classic 1,1′:4′,1″-terphenyl fluorophore. The material exhibits high order and horizontal-dipole ratios, enabling efficient NUV organic light-emitting diodes (OLEDs). Non-doped BB4Ph OLEDs achieved external quantum efficiency (EQE) up to 5.24%, while doped BB4Ph OLEDs with 4P-Cz reached a peak EQE of 6.99%. The material's high photoluminescence quantum yield and light outcoupling efficiency make it a promising candidate for NUV OLED applications.

CS Appl. Mater. Interfaces 2023, 15, 1, 1652–1660

https://doi.org/10.1021/acsami.2c17960

The presence of spontaneous orientation polarization (SOP) in the electron transport layer (ETL) of organic light-emitting devices (OLEDs), induced by the alignment of polar molecules with permanent dipole moments (PDMs), can reduce device efficiency by quenching excitons.

This work quantitatively examines SOP formation in the ETL, considering the impact of film processing conditions and treating the vapor-deposited film as a supercooled glass. The results provide a framework to predict the SOP formation efficiency for polar materials and blends, and in situ measurements reveal that SOP-induced exciton-polaron quenching can be mitigated through optimized processing conditions, leading to improved OLED efficiency.

Optical Outcoupling Calculations. Light outcoupling efficiencies (ηoc) for OLEDs of interest were calculated using the simulation results obtained from Setfos. During the simulation, an isotropic dipole orientation was assumed, and optical constants measured via spectroscopic ellipsometry were used. The IQE for each device is calculated by dividing its ηEQE by its corresponding ηOC.

Fan, XC., Wang, K., Shi, YZ. et al.

Nat. Photon. (2023). https://doi.org/10.1038/s41566-022-01106-8

Researchers developed a new ultrapure green emitter called DBTN-2 for use in organic light-emitting diode (OLED) displays, which has a highly efficient operation due to the introduction of multiple carbazole moieties resulting in a high density of triplet states and a fast rate of reverse intersystem crossing.

An OLED using DBTN-2 as an emitter demonstrated a high photoluminescence quantum yield, strong horizontal dipole orientation, and excellent external quantum efficiency of 35.2% with suppressed efficiency roll-off, meeting commercial requirements for a green OLED display.

The obtained PL intensity angle-dependent patterns were analysed using Setfos with refractive index n, extinction coefficient k values of SF3-TRZ at 520 nm (peak wavelength of DBTN-2) as basic information for simulation.

Carl Degitz , Markus Schmid, Falk May, Jochen Pfister, Armin Auch, Wolfgang Brütting, and Wolfgang Wenzel

Chem. Mater. 2023, 35, 1, 295–303

https://doi.org/10.1021/acs.chemmater.2c03177

Due to their thin amourphous structure, unique electrical properties, and the associated variety of possible applications, OLEDs can now be found in smartphones, TVs, laptops, and wearables. While already big steps have been made in optimizing and understanding the properties influencing the external quantum efficiency (EQE), there is still room for improvement, especially when it comes to finding design principles for new emitter complexes. One contributer to the EQE here is the molecular orientation of the emitter in a given host matrix.

In this work the researchers study the viability of using molecular modeling approaches in sampling these emitter orientations for a set of already published homoleptic Ir carbene emitters and a set of emitter materials synthesized at Merck KGaA, Darmstadt, Germany, comprising both homoleptic and heteroleptic Ir(ppy)3 derivatives.

They combined these simulations with different measurements for the orientation parameter and EQE, all performed with the same material stack under the same conditions. The research team observed a good agreement between simulation and experiment and found that the horizontal orientation of emitter molecules seems to be the main factor contributing to a higher EQE.

The Setfos Optics module was used to calculate the maximum possible EQE for emitter.

Rahman, Md Abdur, Kim, Dong Kyu, Lee, Jong-Kwon and Byun, Ji Young.

Nanophotonics, vol. 11, no. 21, 2022, pp. 4855-4868.

https://doi.org/10.1515/nanoph-2022-0522

Structural colors with tunable properties have extensive applications in surface decoration, arts, absorbers, and optical filters.

CrON/Si3N4/Metal structures show promise for generating vivid structural colors with tunable properties and strong light absorption. Replacing top metallic layer with lossy dielectric prevents degradation from abrasiveness/oxidation. Theoretical and experimental data support these structures' durability and color generation via interference effect and absorption rate

The absorption of each layer and phase shift were calculated using Setfos.

Tasaki, S, Nishimura, K, Toyoshima, H, Masuda, T, Nakamura, M, Nakano, Y, et al.

J Soc Inf Display. 2022; 30( 5): 441– 451.

https://doi.org/10.1002/jsid.1127

The bilayer structure for an emitting layer (EML) was developed to improve performances of a fluorescence blue organic light emitting diode.

By functionally separating the EML into the charge recombination and the triplet–triplet fusion (TTF) zone, we successfully suppressed the quenching of triplet excitons by excess carriers to make more TTF efficient and the local degradation within the EML to make the lifetime longer.

In the bottom emission device with the bilayer EML, 12% of external quantum efficiency (EQE) and 450 h of LT95 were achieved. Furthermore, we achieved over 14% of EQE by optimizing the material combinations.

To estimate the emission ratio from BH1 and BH2, optical simulation by Setfos was conducted at 10 mA/cm2.20

Gregory Burwell, Oskar J. Sandberg, Wei Li, Paul Meredith, Matt Carnie, and Ardalan Armin

Sol. RRL 2200315, 1 , (2022)

DOI: 10.1002/solr.202200315

Compared to their use as organic solar cells (OSCs) for standard outdoor solar harvesting, indoor OPV (IOPV) devices operate at low light intensities and thus demonstrate different area-scaling behavior. In particular, it appears as though the performance of large-area IOPV devices is much less affected by the sheet resistances of the transparent conductive electrodes (a major limit in OSCs), but instead by factors such as their shunt resistance at low light intensities. Herein, the key parameters for improving the efficiency of large area IOPV using drift-diffusion and finite element modeling (FEM) are examined. The scaling behavior at low-light intensities is theoretically and experimentally probed and demonstrated using the model PM6:Y6 system.

Stefano Sem, Sandra Jenatsch, Kleitos Stavrou, Andrew Danos,

Andrew P. Monkman and Beat Ruhstaller

J. Mater. Chem. C, 2022, Advance Article

doi.org/10.1039/D1TC05594A

Thermally-activated delayed fluorescence (TADF) compounds are promising materials used in emissive layers of organic light-emitting diodes (OLEDs). Their main benefit is that they allow the internal quantum efficiency of the OLED to reach up to 100% by converting non-radiative triplet states into radiative singlets. Besides the importance of having a high reverse intersystem-crossing rate, which governs triplet conversion, minimizing the non-radiative decay processes is also extremely important to reach high efficiency. In this study the researchers provide a new method to quantify not only the most important decay rates involved in the TADF process, but also the non-radiative decay rates of both singlet and triplet states individually from transient and steady state experimental optical data.

Setfos was used to perform electro-optical simulations.

Mingyun Kang, Syed Zahid Hassan, Seong-Min Ko, Changwon Choi, Juhee Kim, Santosh K. R. Parumala, Yun-Hi Kim, Yun Hee Jang, Jinhwan Yoon, Dong-Woo Jee, Dae Sung Chung

Advanced Materials

doi.org/10.1002/adma.202200526

When the intensity of the incident light increases, the photocurrents of organic photodiodes (OPDs) exhibit relatively early saturation, due to which OPDs cannot easily detect objects against strong backlights, such as sunlight. In this study, this problem is addressed by introducing a light-intensity-dependent transition of the operation mode, such that the operation mode of the OPD autonomously changes to overcome early photocurrent saturation as the incident light intensity passes the threshold intensity. The photoactive layer is doped with a strategically designed and synthesized molecular switch, 1,2-bis-(2-methyl-5-(4-cyanobiphenyl)-3-thienyl)tetrafluorobenzene (DAB). The proposed OPD exhibits a typical OPD performance with an external quantum efficiency (EQE) of <100% and a photomultiplication behavior with an EQE of >100% under low-intensity and high-intensity light illuminations, respectively, thereby resulting in an extension of the photoresponse linearity to a light intensity of 434 mW cm?2. This unique and reversible transition of the operation mode can be explained by the unbalanced quantum yield of photocyclization/photocycloreversion of the molecular switch. The details of the operation mechanism are discussed in conjunction with various photophysical analyses. Furthermore, they establish a prototype image sensor with an array of molecular-switch-embedded OPD pixels to demonstrate their extremely high sensitivity against strong light illumination.

To further verify the effect of DAB_c on gain generation, the researchers conducted a numerical simulation using the Fluxim’s Setfos software to fit the experimentally obtained OPD data and determine the relevant fitting parameters.

Takeshi Kamijo, Suzanne de Winter, Pradeep Panditha, and Eric Meulenkamp

ACS Applied Electronic Materials 2022 4 (2), 698-706

DOI: 10.1021/acsaelm.1c01116

The transparent conductive electrode (TCE) is a key component of organic light-emitting diodes (OLEDs). High resolution printed metal grids are a promising alternative to indium tin oxide (ITO). We present results for evaporated OLEDs with a printed copper (Cu) grid with line width below 3 μm. The use of a thick doped hole injection layer (HIL) prevented electrical shorts and resulted in good quality OLEDs with acceptable leakage current. We report a detailed analysis of the microscopic uniformity of light emission and compare the measured data with simulations based on finite element modeling (FEM) to investigate various factors that contribute to differences between the Cu grid OLED and ITO reference device. This insight resulted in design rules that enable a luminance of the Cu grid OLED that can potentially equal that of an ITO-based equivalent OLED by using a very fine pitch and narrow line width of 5 μm and 250 nm, respectively, within the capabilities of state-of-the-art printing technology.

The spatial luminance distribution was simulated by LAOSS - large area organic semiconductor simulation software.