Modeling the current-voltage characteristics of bilayer polymer photovoltaic devices

Barker, James; Ramsdale, Catherine

doi:10.1103/physrevb.67.075205

Cited by 265 publications

(264 citation statements)

References 23 publications

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“…The charge densities simulated here are of the order of 10 21 -10 22 m À3 , consistent with other models, 18,43,59 which in a system of this size consists of no more than approximately 10 charge pairs at any time. Animations show that these charge pairs remain in the vicinity of each other for a long time after dissociation, and can track each other within the device.…”

Section: Resultssupporting

confidence: 89%

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Bicontinuous minimal surface nanostructures for polymer blend solar cells

Kimber

Walker

Schröder‐Turk

et al. 2010

Phys. Chem. Chem. Phys.

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This paper presents the first examination of the potential for bicontinuous structures such as the gyroid structure to produce high efficiency solar cells based on conjugated polymers. The solar cell characteristics are predicted by a simulation model that shows how the morphology influences device performance through integration of all the processes occurring in organic photocells in a specified morphology. In bicontinuous phases, the surface defining the interface between the electron and hole transporting phases divides the volume into two disjoint subvolumes. Exciton loss is reduced because the interface at which charge separation occurs permeates the device so excitons have only a short distance to reach the interface. As each of the component phases is connected, charges will be able to reach the electrodes more easily. In simulations of the current-voltage characteristics of organic cells with gyroid, disordered blend and vertical rod (rods normal to the electrodes) morphologies, we find that gyroids have a lower than anticipated performance advantage over disordered blends, and that vertical rods are superior. These results are explored thoroughly, with geminate recombination, i.e. recombination of charges originating from the same exciton, identified as the primary source of loss. Thus, if an appropriate materials choice could reduce geminate recombination, gyroids show great promise for future research and applications.

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Section: Resultssupporting

confidence: 89%

“…10,43,44 From spectral data, this blend has been calculated to absorb 5.8% of the AM 1.5 solar emission spectrum, with an assumed Gaussian optical field profile. 9 We set w ex R 0 6 = 0.02, such that simulations of excitons in a single component material with energetic disorder s = 0.062 eV gives a diffusion length L ex of 6 nm 45 in a lifetime t ex of 500 ps.…”

mentioning

confidence: 99%

Bicontinuous minimal surface nanostructures for polymer blend solar cells

Kimber

Walker

Schröder‐Turk

et al. 2010

Phys. Chem. Chem. Phys.

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“…Prior to the layer deposition, the substrates were ex situ treated with UV ozone for 15 min. The following layer sequence was subsequently deposited: MoO 3 (5 nm)/ID583 (7,14,21,28 nm)/C 60 (35 nm)/Bphen (5 nm)/Ag (100 nm) [see Fig. 1(c)].…”

Section: A Methodsmentioning

confidence: 99%

“…14 An important difference between the two mechanisms is their temperature dependence. Because the CT-states are lower in energy than the free charge carrier pairs, the models of Onsager-Braun 15 and Barker et al 7 assume the CT-state dissociation to be thermally activated. The result is an Arrhenius-like, that is, exponential temperature dependence of the CT-state dissociation, which has not been observed experimentally.…”

Section: Introductionmentioning

confidence: 99%

“…The subsequent dissociation of the CT-state, which has been assumed to be assisted by the cell's internal electric field, has been considered to be the ratelimiting step in the free charge carrier generation process. [7][8][9][10][11] Recently, the picture of the charge-generation process being limited by the CT-state dissociation was questioned. Transient absorption spectroscopy studies on different polymer/methanofullerene blends revealed that the majority of the free charge carriers were not generated via CT-states but directly by ultrafast exciton dissociation.…”

Section: Introductionmentioning

confidence: 99%

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Field-dependent exciton dissociation in organic heterojunction solar cells

et al. 2012

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In organic heterojunction solar cells, the generation of free charge carriers takes place in a multistep process which involves charge transfer (CT) states, that is, bound electron-hole pairs at the interface between donor and acceptor molecules. Past efforts to model the CT-state dissociation during solar cell operation were not able to consistently reproduce the experimentally observed field and temperature dependence. This discrepancy between model and experiment was partly due to the field-dependent free charge carrier collection process, which plays an important role in the widely used bulk heterojunction cell configuration and superimposes a possible field-dependent charge carrier generation process. In order to distinguish between generation and collection of free charge carriers, we propose the planar heterojunction cell configuration as a model system to study the field-dependent charge carrier generation process in organic heterojunction solar cells. We apply this model system to check current CT-state dissociation models against experimental data. Although the models can quantitatively account for the photocurrent's dependence on the applied voltage and the device thickness, they fail to account for the virtually negligible temperature dependence of the field-dependent charge-generation process. This discrepancy is traced back to a common feature of the models: an Arrhenius-like temperature dependence, distinctive of all processes involving a thermally activated jump over an energy barrier. As a solution to the problem, we introduce an exciton dissociation model based on a field-dependent tunnel process and demonstrate its consistency with the experimental observations. Our results indicate that the current microscopic picture of the charge-generation process in organic heterojunction solar cells being limited by the CT-state dissociation process needs to be reconsidered.

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Hybrid Polymer/Nanocrystal Photovoltaic Devices

Greenham

2008

Organic Photovoltaics

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Modeling the current-voltage characteristics of bilayer polymer photovoltaic devices

Cited by 265 publications

References 23 publications

Bicontinuous minimal surface nanostructures for polymer blend solar cells

Bicontinuous minimal surface nanostructures for polymer blend solar cells

Field-dependent exciton dissociation in organic heterojunction solar cells

Hybrid Polymer/Nanocrystal Photovoltaic Devices

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