Thermal effect on the morphology and performance of organic photovoltaics

Kawashima, Eisuke; Fujii, Minoru; Yamashita, Koichi

doi:10.1039/c6cp04019e

Cited by 11 publications

(7 citation statements)

References 59 publications

(91 reference statements)

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“…In this study, we theoretically clarify the mechanism that leads to extended L ex in organic crystals with a strong anisotropy of electronic coupling. The cooperative effects of singlet fission and TTA in the exciton diffusion are analyzed by means of the dynamic Monte Carlo (DMC) simulations. − Our analysis highlights the role of the “S 1 revival mechanism” where L ex is extended via back-and-forth transitions between the isotropically diffusing singlet exciton and long-lived triplet exciton.…”

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confidence: 99%

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Long-Range Exciton Diffusion via Singlet Revival Mechanism

Tamura

Azumaya

Ishikita

2019

J. Phys. Chem. Lett.

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We clarify the mechanism that leads to extended exciton diffusion length in organic materials which exhibit a strong anisotropy of electronic coupling. We analyze the cooperative effects of singlet fission and triplet–triplet annihilation in the exciton diffusion by means of the dynamic Monte Carlo simulations. As a model system, we consider the rubrene crystal which exhibits a long-range exciton diffusion. The deexcitation of the singlet exciton is suppressed by singlet → triplet conversion via singlet fission. Even though the triplet exciton would hardly diffuse along the c-axis in the rubrene crystal (perpendicular to the high mobility plane) because of the small electronic coupling, the regeneration of the singlet exciton via triplet–triplet annihilation enables long-range exciton diffusion along the c-axis. This singlet revival mechanism can extend the overall lifetime and the diffusion length of the exciton, through back-and-forth transitions between an isotropically diffusing singlet exciton and a long-lived triplet exciton.

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confidence: 99%

“…In the DMC simulations, the waiting times, τ, of all possible events are generated at each step as follows: − where W is the rate of each event and X is a random number in the range of 0–1. At each DMC step, the event with the shortest τ occurs, and the simulation time, t , is updated to t + τ.…”

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confidence: 99%

Long-Range Exciton Diffusion via Singlet Revival Mechanism

Tamura

Azumaya

Ishikita

2019

J. Phys. Chem. Lett.

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“…34,[60][61][62] On the basis of these BHJ geometries, drift-diffusion, master-equation, or kinetic Monte Carlo studies have been performed to estimate device properties. 33,63 It would be interesting to extend our model to realistic BHJ conditions, where the effect of complex morphologies could be examined.…”

Section: Atomic-and Mesoscopic-scale Effectsmentioning

confidence: 99%

“…Indeed, recent theoretical and experimental studies have observed such complex BHJ structures and morphologies. [33][34][35] These complex BHJ structures may behave like impurities and obstacles in the exciton dissociation process. In particular, if the size of such impurities becomes mesoscopic in scale, the impurities cannot be ignored.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study on mesoscopic-size impurity effects in the charge separation process of organic photocells

Shimazaki

Tashiro

Nakajima

2018

Phys. Chem. Chem. Phys.

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A bulk-heterojunction structure is often employed to develop high-performance organic photocells, in which the donor and acceptor regions are complexly intertwined. In such situations, mesoscopic-scale islands and peninsulas that compose the donor materials may be formed in the acceptor region. Alternatively, the donor region may extend deeply into the acceptor region. This yields mesoscopic-size impurities that can create obstacles in the charge separation (exciton dissociation) process of organic photocells and prevents the dissociation of excitons (electron-hole pairs). We previously reported on the effect of the cooperative behavior between the hot charge transfer (CT) state and the dimensional (entropy) effect on the charge separation process. In this paper, we discuss the mesoscopic-scale impurity effect on the charge separation process in PCBM acceptor models by considering the hot CT state and dimensional effects. In addition, we discuss atomic-scale effects such as molecular distortions and conformation changes using molecular dynamics (MD) simulations.

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“…a) Electronic mail: dasf@unb.br From a theoretical standpoint, exciton diffusion has been studied by means of Kinetic Monte Carlo (KMC) methods. 10,[13][14][15][16][17] These methods require the probabilities of the Förster transfers as input.…”

Section: Introductionmentioning

confidence: 99%

Modeling temperature dependent singlet exciton dynamics in multilayered organic nanofibers

Sousa

Neto

Kjelstrup‐Hansen

et al. 2018

The Journal of Chemical Physics

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Organic nanofibers have shown potential for application in optoelectronic devices because of the tunability of their optical properties. These properties are influenced by the electronic structure of the molecules that compose the nanofibers and also by the behavior of the excitons generated in the material. Exciton diffusion by means of Förster resonance energy transfer is responsible, for instance, for the change with temperature of colors in the light emitted by systems composed of different types of nanofibers. To study in detail this mechanism, we model temperature dependent singlet exciton dynamics in multilayered organic nanofibers. By simulating absorption and emission spectra, the possible Förster transitions are identified. Then, a kinetic Monte Carlo model is employed in combination with a genetic algorithm to theoretically reproduce time-resolved photoluminescence measurements for several temperatures. This procedure allows for the obtainment of different information regarding exciton diffusion in such a system, including temperature effects on the Förster transfer efficiency and the activation energy of the Förster mechanism. The method is general and may be employed for different systems where exciton diffusion plays a role.

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Thermal effect on the morphology and performance of organic photovoltaics

Abstract: The morphology of organic photovoltaics (OPVs) is a significant factor in improving performance, and establishing a method for controlling morphology is necessary.

Cited by 11 publications

References 59 publications

Long-Range Exciton Diffusion via Singlet Revival Mechanism

Long-Range Exciton Diffusion via Singlet Revival Mechanism

Theoretical study on mesoscopic-size impurity effects in the charge separation process of organic photocells

Modeling temperature dependent singlet exciton dynamics in multilayered organic nanofibers

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