Optical design of organic light emitting diodes

Wang, Z. B.; Helander, Michael G.; Xu, Xinjun; Puzzo, Daniel P.; Qiu, Jacky; Greiner, Mark; Lu, Zhiyun

doi:10.1063/1.3553837

Cited by 37 publications

(17 citation statements)

References 27 publications

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“…Simulation Model : A classical electromagnetic model was adopted, treating the radiative decay of excitonic species as an ensemble of classical electrical dipole antennas radiating electromagnetic power. This was widely used in the simulation of the spontaneous emission inside a structure composed of stacked thin films …”

Section: Methodsmentioning

confidence: 78%

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Optical Energy Losses in Organic–Inorganic Hybrid Perovskite Light‐Emitting Diodes

Shi

Liu

Yuan

et al. 2018

Advanced Optical Materials

111

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easily tunable band gaps. [4][5][6][7] LEDs based on such materials have been attracting increasing attention since the first roomtemperature perovskite LEDs (PeLED) developed in 2014. [13] The development of PeLEDs has progressed very rapidly, realizing a record-high external quantum efficiency (EQE) of 11.7% in 2016. [14] Similar to other LED categories, e.g., organic LEDs (OLEDs) [15] and quantumdot [16,17] LEDs, the EQE of PeLEDs is determined by the internal quantum efficiency (IQE) and light out-coupling efficiency (η), which is expressed asThe IQE is the product of the charge carrier balance (γ), the fraction of excitons capable of radiative decay at room temperature (η S/T ), and the effective radiative quantum yield (q eff ). For 2D perovskite materials with relatively large binding energy, the η S/T could be unity when heavy atoms are involved in the organometallic complex (similar to that in phosphorescent materials [18] ). For 3D perovskite materials with relatively small binding energy, the emission should be bandto-band transitions of free carriers in direct gap semiconductors, and the η S/T term should not be involved in the equation in this case. All in all, this equation shows that the EQE is largely influenced by the η besides the IQE. Thus, studying the limits of η is of great importance for achieving high-EQE PeLEDs.As the fast development of PeLEDs, a conflict appears between the experimental and theoretical results. In general, the η can be estimated according to the ray-optics theory, [19] Light-emitting diodes (LEDs) based on organic-inorganic hybrid perovskites, in particular, 3D and quasi-2D ones, are in the fast development and their external quantum efficiencies (EQEs) have exceeded 10%, making them competitive candidates toward large-area and low-cost light-emitting applications allowing printing techniques. Similar to other LED categories, light out-coupling efficiency is an important parameter determining the EQE of perovskite LEDs (PeLEDs), which, however, is scarcely studied, limiting further efficiency improvement and understanding of PeLEDs. In this work, for the first time, optical energy losses in PeLEDs are investigated through systematic optical simulations, which reveal that the 3D and quasi-2D PeLEDs can achieve theoretically maximum EQEs of ≈25% and ≈20%, respectively, in spite of their high refractive indices. These results are consistent with the reported experimental data. This work presents primary understanding of the optical energy losses in PeLEDs and will spur new developments in the aspects of device engineering and light extraction techniques to boost the EQEs of PeLEDs. Perovskite Light-Emitting DiodesOrganic-inorganic perovskite materials have attracted extensive interest due to their fascinating semiconducting properties, such as high absorption coefficient, long carrier diffusion length, and small exciton binding energy. [1][2][3] Moreover, these materials are easily processed via solution-based techniques, showing great potential applications in low-cost op...

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Section: Methodsmentioning

confidence: 78%

“…al . It was very convincing in the quantitative analysis of the radiated power from the dipoles . Another numerical calculation based on the finite‐difference time‐domain (FDTD) method was implemented.…”

Section: Methodsmentioning

confidence: 99%

Optical Energy Losses in Organic–Inorganic Hybrid Perovskite Light‐Emitting Diodes

Shi

Liu

Yuan

et al. 2018

Advanced Optical Materials

111

View full text Add to dashboard Cite

show abstract

“…[13][14][15] To simplify the calculation, the transfer-matrix method has been adapted in the transmittance and reflectance calculation of multilayer thin-film structures. [16][17][18] Light consists of an electric field component and a magnetic component. In the transfer-matrix method, all the waves propagating in the same direction at the same side of the interface are represented by one electric field.…”

Section: Modelmentioning

confidence: 99%

“…In the transfer-matrix method, electric field amplitudes in coherent layers are correlated via matrix operation, and the light intensity, instead of field amplitudes, has to be employed when correlating waves in the incoherent layer. [16][17][18] Therefore, the coherent layers and incoherent layer have to be calculated separately in our model.…”

Section: Modelmentioning

confidence: 99%

A Method for Efficient Transmittance Spectrum Prediction of Transparent Composite Electrodes

Zhao

Dhar

Alford

2015

JOM

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The interest in indium-free transparent composite electrode (TCE), a thin metal layer embedded between two transparent metal oxide (TMO) layers resulting in TMO/metal/TMO composite structure, has grown recently with the advent of their high figures of merit and its potential application in photovoltaic applications. However, most of the work to date has focused on experimentally producing the best optically transmitting TCE. To better design TCEs and minimize experimental work, it would be useful to develop a model that predicts the optical transmission. In the current work, the transfer-matrix method is employed to calculate the transmittance spectrum of TCE. To validate this approach, the transmittance spectra of TiO 2 /Au/TiO 2 and TiO 2 / Ag/TiO 2 multilayer thin-film TCEs are calculated with use of extracted material parameters. The calculated transmittance spectrum of TiO 2 /Au/TiO 2 matches the measured spectrum quite well. However, the calcualted transmittance of TiO 2 /Ag/TiO 2 is higher than its measured transmittance. The presence of voids in the Ag film is probably responsible for the decreased transmittance of the TiO 2 /Ag/TiO 2 sample, and the continuous Au film in TiO 2 /Au/TiO 2 ensures a good agreement between transmittance prediction and measurement. Our approach is a reliable tool to predict the optical transmittance of TCE with continuous films, and it can efficiently expedite the selection from numerous possible combinations of transparent metal oxides and metals when developing TCEs for future photovoltaic applications. It can also serve as a convenient method to assess the continuity of embedded metal layer.

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“…The outcoupling efficiency (OCE) calculation can be deployed by a simulation method like the ray tracing [37], the transfer matrix method (TMM) [38] or the transmission line method (TLM) [39]. Herein we have adopted the TLM which is thoroughly described in [39].…”

Section: Experimental and Simulation Proceduresmentioning

confidence: 99%

Outcoupling efficiency optimization of phosphorescent and fluorescent based hybrid red, green and blue emitting OLED devices

Vasilopoulou

Georgiadou

Davazoglou

et al. 2016

Phys. Status Solidi C

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The outcoupling efficiency of a hybrid OLED device with a hole‐injection layer formed by either an organic semiconducting material, namely PEDOT:PSS, or an under‐stoichiometric molybdenum oxide is examined. Because the device is considered for the three primary colour emissions, the active layer is composed of a wide band‐gap blue emitting host polymer doped with either phosphorescent or fluorescent guest emitters. Critical parameters, such as the emission zone profile for the doped active layer with either the organic hole‐injection layer or the inorganic metal oxide, are studied. Contour charts have been derived providing the areas of maximum outcoupling efficiency with the corresponding thickness pairs of the active layer and the hole‐injection layer.

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Optical design of organic light emitting diodes

Cited by 37 publications

References 27 publications

Optical Energy Losses in Organic–Inorganic Hybrid Perovskite Light‐Emitting Diodes

Optical Energy Losses in Organic–Inorganic Hybrid Perovskite Light‐Emitting Diodes

A Method for Efficient Transmittance Spectrum Prediction of Transparent Composite Electrodes

Outcoupling efficiency optimization of phosphorescent and fluorescent based hybrid red, green and blue emitting OLED devices

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