publications-olec-list-review

Hou, Min-Chih and Luo, Dian and Huang, Yu-Ting and Liu, Shun-Wei and Lu, Chin-Wei and Chang, Chih-Hao and Su, Hai-Ching

Available at SSRN:

http://dx.doi.org/10.2139/ssrn.4608462

The study explores optimizing light extraction in light-emitting electrochemical cells (LECs) by adjusting the concentration of small TiO2 nanoparticles in a diffuser film. Enhanced roughness and appropriate refractive index improve light outcoupling, offering potential for higher device efficiencies in LEC lighting applications.

How Setfos was used

Fluxim's Setfos software was crucial in simulating light extraction efficiencies from LECs. By varying the TiO2 nanoparticle concentration in diffuser films, Setfos helped ascertain the optimal conditions for light outcoupling, demonstrating a significant enhancement in device performance with properly configured diffuser films.

X. Zhang, J. Ràfols-Ribé, J. Mindemark, S. Tang, M. Lindh, E. Gracia-Espino, C. Larsen, L. Edman, Adv. Mater. 2024, 2310156.

https://doi.org/10.1002/adma.202310156

The paper by Zhang et al. investigates the decrease in emission efficiency at higher currents in light-emitting electrochemical cells (LECs). It focuses on identifying and quantifying the major factors causing this efficiency drop, such as outcoupling efficiency and exciton quenching. The study presents a method to analyze these factors, contributing to the design of more efficient, high-luminance LEC devices.

How Setfos was used

Setfos was used for modeling in the study. This software simulated the structure of the light-emitting electrochemical cell (LEC) device, including various components like the glass substrate, ITO anode, active material, and Al cathode. The software modeled excitons as emissive electrical dipoles. It was particularly used for simulating the electroluminescence (EL) spectra and EL intensity to determine the position of the emissive p-n junction in the device, using a delta function exciton distribution in a transparent, non-doped active material with the wavelength-dependent refractive index of pristine Super Yellow

S. Tang, J. M. dos Santos, J. Ràfols-Ribé, J. Wang, E. Zysman-Colman, L. Edman, Adv. Funct. Mater. 2023, 33, 2306170. https://doi.org/10.1002/adfm.202306170

The paper introduces MR-TADF emitters into light-emitting electrochemical cells (LECs) for narrowband and efficient emission. It demonstrates a metal-free MR-TADF LEC delivering blue light with a narrow full-width-at-half-maximum (FWHM) of 31 nm, a high external quantum efficiency of 3.8%, and significant electrochemical doping capacity.

How Setfos was used

Setfos was used to perform optical simulations, helping to understand and optimize the emission and efficiency of the device by simulating the position of emissive dipoles within the active material.

Luo, D., Hou, M.-C., Wang, K.-Y., Chang, C.-H., Liu, S.-W., Lu, C.-W. and Su, H.-C. (2023),

Adv. Mater. Technol., 8: 2300563. https://doi.org/10.1002/admt.202300563

The research presents a tandem white OLED/LEC hybrid device, combining a red OLED and a blue LEC, which simplifies fabrication compared to multi-layered OLEDs. The device includes a charge-generating layer (CGL) that not only links the two, but also improves carrier balance, leading to an external quantum efficiency (EQE) of 21.53%. Efficiency jumps to 37.88% when using a diffusive substrate. This demonstrates a simpler yet highly efficient structure, offering promising potential for cost-effective lighting solutions.

How Setfos was used

To clarify the relationship between the recombination zone position and the optical mode distribution for Device B, Device R, and Device T. The optical simulation software Setfos was employed as the analysis tool as was the optical mode distribution of the devices.

Huseynova, G., Ràfols-Ribé, J., Auroux, E. et al. Sci Rep 13, 11457 (2023).

https://doi.org/10.1038/s41598-023-38006-y

The performance of light-emitting electrochemical cells (LECs) is greatly influenced by the position of the emissive p–n junction within the device. A new "chemical pre-doping" method that incorporates a reductant into the active material ink shifts the p–n junction closer to the anode, which enhances emission efficiency and device stability. This approach offers a practical solution for optimizing the spatial configuration of p–n junctions in LECs.

How Setfos was used

The optical simulations were carried out with Setfos. The position of the emissive p–n junction within the active material was determined by minimizing the root mean square error between the simulated and the measured angle-dependent EL data.

The exciton formation rate profile in the interelectrode gap was determined with the drift–diffusion module of the same software, and the simulated three-layer device featured an ITO anode (thickness = 145 nm), an active material (thickness = 150 nm), and an Al cathode.

Ràfols-Ribé, J., Hänisch, C., Larsen, C., Reineke, S. and Edman, L. Adv. Mater. Technol. 2202120.

https://doi.org/10.1002/admt.202202120

This study explores emissive dipole orientation in light-emitting electrochemical cells (LECs) affecting emission efficiency. Using a destructive-interference microcavity method, researchers find ≈95% horizontal dipole orientation in LECs with Super Yellow emitters, enabling efficient photon outcoupling, despite strong perpendicular electric fields and ion motion.

LEC Optical Modeling and Fitting: The LEC devices were simulated with a Setfos.

M. Diethelm, A. Devižis, W.-H. Hu, T. Zhang, R. Furrer, C. Vael, S. Jenatsch, F. Nüesch, R. Hany

Adv. Funct. Mater. 2022, 32, 2203643. https://doi.org/10.1002/adfm.202203643

This research investigates the impact of electron and hole traps on the performance and lifespan of polymer light-emitting electrochemical cells (PLECs). The study aims to identify and analyze the role of these traps in PLECs, drawing parallels with their known impact on polymer light-emitting diodes (PLEDs).

The researchers fabricated PLECs using a super yellow (SY) polymer as the emitting material and employed various experimental techniques, including electrical driving and breaks, light irradiation, and long-term absorption and capacitance measurements. Optical and electrical simulations using Setfos provided further insights into device behavior.

The findings reveal that electron traps in PLECs share similar characteristics with those in PLEDs, suggesting a common origin in the semiconducting polymer. Notably, the study identifies two types of hole traps in PLECs: one type present in the intrinsic region, mirroring PLED behavior, and another type forming at the interface of the intrinsic and p-doped regions, specific to the PLEC architecture.

This research highlights the significant role of charge traps in limiting PLEC performance and longevity. The findings emphasize the need for strategies beyond conventional approaches to enhance PLEC stability, urging a focus on addressing the fundamental limitations posed by charge traps within the light-emitting polymer itself.

How Setfos Was Used

Setfos was used to perform optical and electrical simulations of the PLEC devices to better understand their properties, such as luminance versus emitter position.

How Paios Was Used

Paios was used to perform several different types of measurements on the PLEC devices:

Impedance measurements: Specifically, impedance measurements at 0 V with an alternating 70 mV signal were taken to determine the capacitance transients of the devices.

Current and light intensity transient measurements: The Paios measurement system was also used to measure how the current and light intensity changed over time. The light intensity was measured by using a photodiode to measure the photovoltage, and the relationship between the measured photovoltage and the corresponding radiance/luminance is explained in a different source.

How Phelos Was Used

Phelos was used to take angular-dependent electroluminescence (EL) measurements of the PLEC devices.