All-atom simulation of molecular orientation in vapor-deposited organic light-emitting diodes

Youn, Yong; Yoo, Do-Sik; Song, Hochul; Kang, Youngho; Kim, Kye Yeop; Jeon, Sang-Ho; Cho, Youngmi; Chae, Kyungchan; Han, Seungwu

doi:10.1039/c7tc05278b

Cited by 31 publications

(34 citation statements)

References 53 publications

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“…One challenge underlying all theoretical efforts to simulate organic electronics applications and to computationally design new materials is the inherent multiscale nature of all models of organic electronics (see Figure 1). [46][47][48][49] The quantitative prediction of thin film properties like the charge carrier mobility ( Figure 1b) [39,[50][51][52][53] or device properties (Figure 1c) [54] requires knowledge about the electronic structure of each individual molecule in a disordered system comprising of thousands of molecules. [46][47][48][49] The quantitative prediction of thin film properties like the charge carrier mobility ( Figure 1b) [39,[50][51][52][53] or device properties (Figure 1c) [54] requires knowledge about the electronic structure of each individual molecule in a disordered system comprising of thousands of molecules.…”

Section: Introductionmentioning

confidence: 99%

Toward Design of Novel Materials for Organic Electronics

et al. 2019

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organic/inorganic perovskites solar cells [6] to printable electronic circuits based on organic field-effect transistors (OFETs). [7] While OLED displays outperform their inorganic counterparts in terms of energy efficiency, [8] scientific and technical challenges concerning the stability and processability of the organic materials used in large-area OLEDs and organic solar cells remain. New challenges arise from applications, such as displays on flexible substrates, OLED lightning, large area displays as well as for printable or solution processable larger area solar cells. [8] Many of the remaining challenges are material related, e.g., the low mobility of charge carriers in organic materials in general and in amorphous organic semiconductors in particular. There are other materials related issues, such as limited OLED life times due to unstable blue hosts and emitters, [9] low fill factors, and therefore reduced power conversion efficiencies of organic solar cells, [10,11] low conductivity and high costs of organic charge transport layers of perovskite solar cells [6,12,13] and low conductivity and hard processability of crystalline OFET materials. [14] Conductivity and injection can be improved by doping the organic thin films with molecular dopants with high electron affinities (p-type) [15] or low ionization energies (n-type). [16] The doping mechanism of organic materials is in many cases not well understood, [17] making material and device optimization a costly experimental endeavor.The development of better materials is presently based on chemical insight, in part guided by theoretical understanding, or the experimental screening of large numbers of compounds. Given the size of the potentially available chemical space this remains a costly and time-consuming approach. Recent successes in experimental design of novel materials and concepts include the development of a stable strong molecular n-type dopant, [16] a study about the quantitative relation between interaction parameter, miscibility, and function of conjugated polymer donors and small-molecule acceptors for bulk heterojunctions as used in organic solar cells [18] the development of a universal strategy for ohmic hole injection into organic semiconductors with high ionization energies [19] and many others. [20][21][22][23][24][25] Another example is the development of strategies to harvest triplet excitons in organic light emitting diodes. For this purpose, novel classes of emitter molecules were developed, which include thermally activated delayed fluorescence (TADF)-based molecules, [26][27][28][29][30][31][32] rotationally accessed spin-state inversion, [33] and radical-based emitters. [34] Materials for organic electronics are presently used in prominent applications, such as displays in mobile devices, while being intensely researched for other purposes, such as organic photovoltaics, large-area devices, and thin-film transistors. Many of the challenges to improve and optimize these applications are material related and there is a nearly inf...

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Section: Introductionmentioning

confidence: 99%

Toward Design of Novel Materials for Organic Electronics

et al. 2019

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“…The understanding of the driving forces regulating molecular orientation is mandatory to optimize material properties, such as charge transport, and to design processes and/or compounds to improve device efficiency. In this matter, the molecular dynamics (MD) at atomic resolution is a powerful computational method able to rationalize the microscopic origin of the molecular preferred orientation, [ 17–26 ] and several studies have been reported to successfully study interfacial properties and molecular arrangement of OLED materials. [ 7,18,20,27 ] For a general description of the challenges and the strategies currently used in the computational modeling of OLED materials, we refer the interested reader to a recent perspective [ 19 ] and the references therein.…”

Section: Introductionmentioning

confidence: 99%

Bidimensional H‐Bond Network Promotes Structural Order and Electron Transport in BPyMPMs Molecular Semiconductor

Correa

Giunchi

Muccioli

et al. 2021

Advcd Theory and Sims

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The presence of a hydrogen bond (H‐Bond) network has been proved to impact significantly the efficiency of organic light‐emitting diode (OLED) devices by promoting molecular orientation and structural anisotropy in thin films. The design of specific compounds to control H‐Bond network formation in an amorphous material, and hence to improve OLED performances, is needed. A successful example is given by the bi‐pyridyl‐based family n‐type of organic semiconductors named BPyMPM. The experimental evidences demonstrate a surprisingly higher electron mobility in thin film composed of 4,6‐bis(3,5‐di(pyridine‐4‐yl)phenyl)‐2‐methylpyrimidine (B4PyMPM (B4)), which is almost two order of magnitude higher than mobility measured for very similar member of the family, 4,6‐bis(3,5‐di(pyridine‐2‐yl)phenyl)‐2‐methylpyrimidine (B2PyMPM (B2)). Herein, a comprehensive computational study is presented, wherein classical and ab initio methods are combined, to investigate the 2D H‐Bond network in B4 and B2 thin films. The results indicate that B4 forms a larger number of intermolecular C‐H···N H‐Bonds that promote a higher orientational and positional order in B4 films, and superior electron transport properties.

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“…74 Note that emitting layers are typically (meta)stable, disordered or partially ordered glasses, and host and emitter molecules themselves (Figure 1 scheme pioneered by some of us for the vapor deposition of organic crystalline semiconductors, 76,77 have gained increasing popularity in the OLED research field. [78][79][80][81] The origin of this trend is two-fold: on the one hand, real TADF-based active layers are in fact prepared most often by co-deposition of (at least) one host semiconductor and a guest TADF emitter, 82 and on the other hand, since these films are amorphous, it is difficult to validate the simulation results versus experimental structural data, and it is tempting to believe that mimicking the experimental process could improve the quality of the predictions. Indeed, one of the open questions in the field is how important is the simulation procedure in determining the final morphology, and in turn how does it influence the calculated electronic properties.…”

mentioning

confidence: 99%

Computational Design of Thermally Activated Delayed Fluorescence Materials: The Challenges Ahead

Olivier

Sancho‐García

Muccioli

et al. 2018

J. Phys. Chem. Lett.

144

188

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Thermally activated delayed fluorescence (TADF) offers the premise for all-organic light emitting diodes with quantum efficiencies competing those of transition metal-based phosphorescent devices. While computational efforts have so far largely focused on gas-phase calculations of singlet and triplet excitation energies, the design of TADF materials requires multiple methodological developments targeting among others a quantitative description of electronic excitation energetics, fully accounting for environmental electrostatics and molecular conformational effects, the accurate assessment of the quantum-mechanical interactions that trigger the elementary electronic processes involved in TADF, as well as a robust picture for the dynamics of these fundamental processes. In this perspective, we describe some recent progress along those lines and highlight the main challenges ahead for modeling, which we hope will be useful to the whole TADF community.

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All-atom simulation of molecular orientation in vapor-deposited organic light-emitting diodes

Abstract: Using all-atom simulation of vapor deposition, we theoretically investigate how the molecular orientation depends on various factors such as the substrate temperature, molecular shape, and material composition.

Cited by 31 publications

References 53 publications

Toward Design of Novel Materials for Organic Electronics

Toward Design of Novel Materials for Organic Electronics

Bidimensional H‐Bond Network Promotes Structural Order and Electron Transport in BPyMPMs Molecular Semiconductor

Computational Design of Thermally Activated Delayed Fluorescence Materials: The Challenges Ahead

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