Significantly Reduced Bimolecular Recombination in a Novel Silole‐Based Polymer: Fullerene Blend

Clarke, Tracey M.; Rodovsky, Deanna B.; Herzing, Andrew A.; Peet, Jeff; Dennler, Gilles; DeLongchamp, Dean M.; Lungenschmied, Christoph; Mozer, Attila J.

doi:10.1002/aenm.201100390

Cited by 61 publications

(72 citation statements)

References 27 publications

(71 reference statements)

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“…Prior to light degradation, the calculated mobility is ~ 8 x 10 -4 cm 2 V -1 s -1 ; this value is higher than that previously published. [10] This could be because in this study the device area was reduced by a factor of three (to ~ 5 mm 2 ) in order to minimise RC limitations and better resolve t max . Furthermore, the devices measured here have much higher efficiencies (4.4 % rather than the previous 3.0 % [10] ).…”

Section: Photo-celivmentioning

confidence: 99%

“…. [9][10][11][12][13] This polymer, although it does not attain the high efficiencies of PCDTBT:PCBM in thin (< 100 nm) active layer thickness devices, has particularly interesting characteristics in thick (> 200 nm active layer) devices. KP115:PCBM devices, which can reach efficiencies of 5 %, possess the rare but highly desirable characteristic that the active layer can be considerably thicker without a detrimental effect on the efficiency.…”

Section: Introductionmentioning

confidence: 99%

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Photodegradation in Encapsulated Silole‐Based Polymer: PCBM Solar Cells Investigated using Transient Absorption Spectroscopy and Charge Extraction Measurements

Clarke

Lungenschmied²,

Peet³

et al. 2013

Advanced Energy Materials

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. (2013). Photodegradation in encapsulated silole-based polymer: Pcbm solar cells investigated using transient absorption spectroscopy and charge extraction measurements. Advanced Energy Materials, 3 (11), 1473-1483. Photodegradation in encapsulated silole-based polymer: Pcbm solar cells investigated using transient absorption spectroscopy and charge extraction measurements AbstractLight induced degradation has been observed in the performance of organic solar cells in the absence of oxygen and a detailed analysis of the effect of this photodegradation on optical and electrical features has been accomplished. This photodegradation study has been performed on encapsulated photovoltaic blend devices comprised of the silole-based donor-acceptor polymer KP115 blended with [6,6]-phenyl C61-butyric acid methyl ester (PCBM). Photodegradation induces an almost 20% decrease in power conversion efficiency, primarily as a result of a reduction in short circuit current, JSC. The initial burn-in phase of the photodegradation has been examined using a combination of transient absorption spectroscopy and charge extraction measurements, including photo-CELIV (charge extraction by linearly increasing voltage) and timeresolved charge extraction using a nanosecond switch. These measurements reveal a bimodal KP115 polaron population, comprised of both delocalised and localised/trapped charge carriers. The photodegradation results are consistent with an alteration of this bimodal KP115 polaron population, with the polarons becoming trapped in a broader, deeper density of localised states. Under laser illumination and at open circuit conditions, this enhanced trapping after light soaking inhibits charges from undergoing bimolecular recombination, leading to higher extracted charge densities at long times. At the lower charge densities operating at short circuit conditions and under continuous white light illumination, where bimolecular recombination is much less significant, the JSC decreases after light soaking due to a reduction in the efficiency of trapped charge carrier extraction. Disciplines Engineering | Physical Sciences and Mathematics Publication DetailsClarke, T. M., Lungenschmied, C., Peet, J., Drolet, N., Sunahara, K., Furube, A. & Mozer, A. J. (2013

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Section: Photo-celivmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photodegradation in Encapsulated Silole‐Based Polymer: PCBM Solar Cells Investigated using Transient Absorption Spectroscopy and Charge Extraction Measurements

Clarke

Lungenschmied²,

Peet³

et al. 2013

Advanced Energy Materials

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“…22,23 Most importantly, in some blends, the recombination rate has been found to be several orders of magnitude less than what is predicted by the Langevin model. 8,[24][25][26][27][28][29][30][31][32][33] As a result, many of these studies have determined the Langevin reduction factor (ζ), where…”

mentioning

confidence: 99%

“…However, in other seemingly similar systems, recombination rates much closer to the Langevin model were observed. 14,26,27,[34][35][36] Even blends with very similar morphology can have dramatically different recombination rates.…”

mentioning

confidence: 99%

Charge carrier concentration dependence of encounter-limited bimolecular recombination in phase-separated organic semiconductor blends

2016

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Understanding how the complex intermolecular-and nano-structure present in organic semiconductor donor-acceptor blends impacts charge carrier motion, interactions, and recombination behavior is a critical fundamental issue with a particularly major impact on organic photovoltaic applications. In this study, kinetic Monte Carlo (KMC) simulations are used to numerically quantify the complex bimolecular charge carrier recombination behavior in idealized phase-separated blends. Recent KMC simulations have identified how the encounter-limited bimolecular recombination rate in these blends deviates from the often used Langevin model and have been used to construct the new power mean mobility model. Here, we make a challenging but crucial expansion to this work by determining the charge carrier concentration dependence of the encounter-limited bimolecular recombination coefficient. In doing so, we find that an accurate treatment of the long-range electrostatic interactions between charge carriers is critical, and we further argue that many previous KMC simulation studies have used a Coulomb cutoff radius that is too small, which causes a significant overestimation of the recombination rate. To shed more light on this issue, we determine the minimum cutoff radius required to reach an accuracy of less than ±10% as a function of the domain size and the charge carrier concentration and then use this knowledge to accurately quantify the charge carrier concentration dependence of the recombination rate. Using these rigorous methods, we finally show that the parameters of the power mean mobility model are determined by a newly identified dimensionless ratio of the domain size to the average charge carrier separation distance.

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“…Assuming a reasonable built-in eld, it is found that the IQE for c b ¼ 0 drastically depends on the non-Langevin factor: 30 In summary, Fig. 6 shows that in the case of Si-PCPDTBT reduced mobility and enhanced background carrier concentration easily account for the observed loss of J SC upon photo-oxidation of the active layer (see Fig.…”

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confidence: 99%

The effect of oxygen induced degradation on charge carrier dynamics in P3HT:PCBM and Si-PCPDTBT:PCBM thin films and solar cells

et al. 2015

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Due to their light weight, transparency and flexibility, organic photovoltaic (OPV) devices are ideal for building integration. As this application requires solar cell life times of more than twenty years and oxygen ingress cannot be avoided at competitive cost on this time scale, OPV modules must be intrinsically stabilized against photo-oxidation. To this end, the mechanism of rapid performance loss of OSCs due to oxygen-induced degradation must be understood. Here, we combine transient absorption experiments with electrical studies in P3HT:PCBM and Si-PCPDTBT:PCBM thin films and solar cells after controlled photo-oxidation, studying charge carrier dynamics on the femtosecond to millisecond time scale. We find that oxygen-induced degradation does not significantly influence charge generation, while its influence on charge recombination is strong in both materials. A dramatic retardation of charge recombination already at low levels of oxygen-induced degradation is attributed to a substantial reduction of charge mobilities. We also observe a significant increase of the background concentration of charge carriers with the level of degradation, which leads to a crossover from second order towards pseudo-first order recombination behaviour. Extraction is shown to be retarded even more strongly than recombination, possibly by a reduction of the extraction field by the background carriers. Overall, the recombination yield is increased with degradation, explaining the strong performance loss already at low degradation levels.

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Significantly Reduced Bimolecular Recombination in a Novel Silole‐Based Polymer: Fullerene Blend

Cited by 61 publications

References 27 publications

Photodegradation in Encapsulated Silole‐Based Polymer: PCBM Solar Cells Investigated using Transient Absorption Spectroscopy and Charge Extraction Measurements

Photodegradation in Encapsulated Silole‐Based Polymer: PCBM Solar Cells Investigated using Transient Absorption Spectroscopy and Charge Extraction Measurements

Charge carrier concentration dependence of encounter-limited bimolecular recombination in phase-separated organic semiconductor blends

The effect of oxygen induced degradation on charge carrier dynamics in P3HT:PCBM and Si-PCPDTBT:PCBM thin films and solar cells

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