Monte Carlo simulation of bimolecular exciton annihilation in an energetically random hopping system

Scheidler, M.; Cleve, B.; Bäßler, H.; Thomas, P.

doi:10.1016/0009-2614(94)87107-8

Cited by 45 publications

(34 citation statements)

References 13 publications

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“…4f). Such power-law-type time dependence of k 2 is consistent to the results from Monte-Carlo-simulations on bimolecular recombination in disordered materials in the presence of Gaussian or exponential energetic disorder1350. These particular decay kinetics were attributed to the continuous thermalization of carriers in the inhomogeneously broadened DOS, which progressively slows down carrier motion.…”

Section: Discussionsupporting

confidence: 85%

Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend

Kurpiers

Neher

2016

Sci Rep

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Recombination of free charge is a key process limiting the performance of solar cells. For low mobility materials, such as organic semiconductors, the kinetics of non-geminate recombination (NGR) is strongly linked to the motion of charges. As these materials possess significant disorder, thermalization of photogenerated carriers in the inhomogeneously broadened density of state distribution is an unavoidable process. Despite its general importance, knowledge about the kinetics of NGR in complete organic solar cells is rather limited. We employ time delayed collection field (TDCF) experiments to study the recombination of photogenerated charge in the high-performance polymer:fullerene blend PCDTBT:PCBM. NGR in the bulk of this amorphous blend is shown to be highly dispersive, with a continuous reduction of the recombination coefficient throughout the entire time scale, until all charge carriers have either been extracted or recombined. Rapid, contact-mediated recombination is identified as an additional loss channel, which, if not properly taken into account, would erroneously suggest a pronounced field dependence of charge generation. These findings are in stark contrast to the results of TDCF experiments on photovoltaic devices made from ordered blends, such as P3HT:PCBM, where non-dispersive recombination was proven to dominate the charge carrier dynamics under application relevant conditions.

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Section: Discussionsupporting

confidence: 85%

Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend

Kurpiers

Neher

2016

Sci Rep

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“…This differs considerably from previous observations of triplet dynamics in polyfluorene 11 and N,N -di(1-naphthyl)-N,N -diphenylbenzidine, 31 where triplets are generated via the intersystem crossing route. In the latter cases, the TF is hopping limited, and hence temperature dependent, 11,31,33,34 leading to a DF decay with substantial differences at different temperatures. Normally, the change in the slope of DF decay is observed with a change of temperature due to a change from dispersive (power law with a slope of −1) to nondispersive (power law with a slope of −2) triplet exciton migration.…”

Section: Nanosecond Luminescence Spectroscopymentioning

confidence: 99%

Competition between polaron pair formation and singlet fission observed in amorphous rubrene films

et al. 2013

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In this paper, we investigate excited state dynamics in amorphous rubrene vacuum sublimed films. We report the direct observation of singlet fission in amorphous rubrene films. We have determined the fission rate to be >2.5 × 10 12 s −1 . Simultaneously, we observe strong polaron pair absorption and propose that polaron pair formation could be competing with singlet fission. Another possible conclusion from our experiments could be that two triplets from singlet fission might arise via polaron pairs. In either case, polaron pairs play an important role in singlet fission in an amorphous rubrene film. We also observe that triplets created by singlet fission fuse to regenerate a singlet, giving delayed fluorescence (DF) scaling linearly with initial laser energy (i.e., one singlet gives two triplets and two triplets give back one singlet). This is a strong evidence of S n 1 → 2T 1 . We did not observe substantial temperature dependence of DF decay curve shape, indicating that triplet migration in amorphous rubrene films is not hopping limited and that triplets undergo fusion before their migration.

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“…[25] This could indeed lead to a power law with an exponent of n = -1 for the decay of delayed fluorescence as Monte Carlo simulations on a Gaussian density of states have predicted for the dispersive regime of triplet energy migration. [26] However, it is not the intention of the present work to contribute to the ongoing discussion. Figure 5 includes also the fluorescence decay pattern of a thin film of fully-arylated poly(ladder-type tetraphenylene).…”

Section: Time-resolved Photoluminescence Spectroscopymentioning

confidence: 99%

Photophysical Properties of a Series of Poly(ladder‐type phenylene)s

Laquai

Mishra

Ribas

et al. 2007

Adv Funct Materials

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The photophysical properties, i.e., the fluorescence and phosphorescence of a series of blue light‐emitting poly(ladder‐type phenylene)s have been investigated employing continuous‐wave (cw) and time‐resolved photoluminescence (PL) spectroscopy in solid state and dilute solution. The chemically well‐defined polymers vary from two to five bridged phenyl‐rings per monomer unit bearing aryl‐ or alkyl‐substitution at the bridge‐head carbon atoms. It has been found that the fluorescence energy of the polymers and of the corresponding monomers deviates from a simple 1/N dependence, if the number N of bridged‐phenylene rings is increased beyond a certain limit. Time‐resolved fluorescence spectroscopy on thin films showed that apart from the blue fluorescence of the polymers an additional lower energy emission feature exists, which cannot be assigned to keto‐defects and which seems to be an inherent solid state property of this class of materials. Delayed time‐resolved photoluminescence spectroscopy allowed the detection of phosphorescence energies and lifetimes for all investigated polymers. Photoinduced absorption spectroscopy on thin films showed that the triplet‐triplet absorption red‐shifts with increasing monomer length but reaches a constant value for polymers with N ≥ 4. Amplification of light via amplified spontaneous emission (ASE) from thin film slab waveguide structures could be demonstrated for all ladder‐type polymers but the onset threshold value for ASE varies significantly with the polymer structure.

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Monte Carlo simulation of bimolecular exciton annihilation in an energetically random hopping system

Cited by 45 publications

References 13 publications

Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend

Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend

Competition between polaron pair formation and singlet fission observed in amorphous rubrene films

Photophysical Properties of a Series of Poly(ladder‐type phenylene)s

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