Charge Carrier Localization and Transport in Organic Semiconductors: Insights from Atomistic Multiscale Simulations

Mladenović, Mirjana; Vukmirović, Nenad

doi:10.1002/adfm.201402435

Cited by 50 publications

(46 citation statements)

References 100 publications

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“…[176] kMC simulations also helped to gain insights into the polaron distribution in doped organic semiconductors, such as ZnPc:F 6 -TCNNQ, [177] and disordered polymers, where polaron delocalization plays an important role. [178,179] …”

Section: Multiscale Modelingmentioning

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: Multiscale Modelingmentioning

confidence: 99%

Toward Design of Novel Materials for Organic Electronics

et al. 2019

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“…[20][21][22][23][28][29][30] However, at the best of our knowledge, this work represents the first attempt to apply such methodology to HTMs of interest for energy devices. In this respect, we do believe that the discussed theoretical results, consistent with the available experimental ones, can be useful to design new HTMs with improved performances.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Investigation of Hole Transporter Materials for Energy Devices

et al. 2015

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We present combined MD-DFT calculations to investigate the electronic, optical and charge transport properties of six triphenylamine based Hole Transporter Materials (HTM) used in solid-state dye sensitized solar cells (ssDSSC), including the state of the art material in this field, 2,2',7,7'-Tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'spirobifluorene (Spiro-OMeTAD). We find that all the studied materials present typical features of a HTM: 1) delocalized Highest Occupied Molecular Orbital (HOMO); 2) hole reorganization energies higher than the electronic ones; 3) transparency in the visible region of the electromagnetic spectrum. Among the investigated compounds, 4-(4-phenyl-4-α-naphthylbutadienyl)-N,N-di(4-tolyl)-phenylamine (HTM1) shows the most promising features: a low HOMO energy level that favors high open circuit voltage in solar cells, high adiabatic ionization potential ensuring great stability in terms of resistance to ionization and small exciton binding energy. Our results also indicate that the presence of a butadiene moiety in HTM1 is somehow responsible for a higher molecular flexibility, thus favoring the pore filling of the semiconductor in ssDSSC.Finally, its optimal charge delocalization favors the overlap of the atomic orbitals, thus enhancing the electronic couplings, while its low energetic disorder causes a high hole mobility in the amorphous phase. The obtained results are in qualitative and quantitative agreement with the experimental data and suggest that the current computational approach could be further employed to obtain valuable insights for the design of new HTMs aiming at improving the performances of presently available ssDSSC. . (8) Kroeze, J. E.; Hirata, N.; Schmidt-Mende, L.; Orizu, C.; Ogier, S. D.; Carr, K.; Grätzel, M.; Durrant, J. R. Parameters Influencing Charge Separation in Solid-State 21

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“…What was once thought to be fairly clear-cut interfaces between the donor and acceptor components, has been replaced by a complex morphological picture that includes pure domains with different extents of ordered and disordered packing as well as intermixed regions of the two materials where charge generation primarily occurs. [16][17][18][19][20][21][22][23][24][25][26][27][28] As we discussed recently, 29 the energetic landscape at a surface (i.e., organic-vacuum interface) differs significantly from the bulk of a crystalline material. One would expect, furthermore, the addition of a second organic component to further complicate the landscape.…”

Section: Introductionmentioning

confidence: 93%

Polarization Energies at Organic–Organic Interfaces: Impact on the Charge Separation Barrier at Donor–Acceptor Interfaces in Organic Solar Cells

Ryno

Risko

et al. 2016

ACS Appl. Mater. Interfaces

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We probe the energetic landscape at a model pentacene/fullerene-C 60 interface to investigate the interactions between positive and negative charges, which are critical to the processes of charge separation and recombination in organic solar cells. Using a polarizable force field, we find that polarization energy, i.e. the stabilization a charge feels due to its environment, is larger at the interface than in the bulk for both a positive and a negative charge. The combination of the charge being more stabilized at the interface and the Coulomb attraction between the charges, results in a barrier to charge separation at the pentacene-C 60 interface that can be in excess of 0.7 eV for static configurations of the donor and acceptor locations. However, the impact of molecular motions, i.e., the dynamics, at the interface at room temperature results in a distribution of polarization energies and in charge separation barriers that can be significantly reduced. The dynamic nature of the interface is thus critical, with the polarization energy distributions indicating that sites along the interface shift in time between favorable and unfavorable configurations for charge separation.

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Charge Carrier Localization and Transport in Organic Semiconductors: Insights from Atomistic Multiscale Simulations

Cited by 50 publications

References 100 publications

Toward Design of Novel Materials for Organic Electronics

Toward Design of Novel Materials for Organic Electronics

Theoretical Investigation of Hole Transporter Materials for Energy Devices

Polarization Energies at Organic–Organic Interfaces: Impact on the Charge Separation Barrier at Donor–Acceptor Interfaces in Organic Solar Cells

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