Effect of Imbalanced Charge Transport on the Interplay of Surface and Bulk Recombination in Organic Solar Cells

Scheunemann, Dorothea; Wilken, Sebastian; Sandberg, Oskar J.; Österbacka, Ronald; Schiek, Manuela

doi:10.1103/physrevapplied.11.054090

Cited by 24 publications

(33 citation statements)

References 41 publications

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“…We have recently used a numerical drift–diffusion model to discuss how imbalanced charge transport affects the open‐circuit voltage . Here, we will apply the same model to study the charge collection under short‐circuit conditions.…”

Section: Resultsmentioning

confidence: 99%

“…Space charge effects in OPVs may occur due to (unintentional) doping, either within the active layer or in the vicinity of the contacts . Another source of space charge is imbalanced charge transport . If there is a significant mismatch between the mobility of electrons (

μ_{normaln}

) and holes (

μ_{normalp}

) in the active layer, charges will accumulate at the electrode extracting the slower carrier.…”

Section: Introductionmentioning

confidence: 99%

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Watching Space Charge Build Up in an Organic Solar Cell

et al. 2020

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Space charge effects can significantly degrade charge collection in organic photovoltaics (OPVs), especially in thick‐film devices. The two main causes of space charge are doping and imbalanced transport. Although these are completely different phenomena, they lead to the same voltage dependence of the photocurrent, making them difficult to distinguish. Herein, a method is introduced on how the build‐up of space charge due to imbalanced transport can be monitored in a real operating organic solar cell. The method is based on the reconstruction of quantum efficiency spectra and requires only optical input parameters that are straightforward to measure. This makes it suitable for the screening of new OPV materials. Furthermore, numerical and analytical means are derived to predict the impact of imbalanced transport on charge collection. It is shown that when charge recombination is sufficiently reduced, balanced transport is not a necessary condition for efficient thick‐film OPVs.

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Section: Resultsmentioning

confidence: 99%

μ_{normaln}

) and holes (

μ_{normalp}

) in the active layer, charges will accumulate at the electrode extracting the slower carrier.…”

Section: Introductionmentioning

confidence: 99%

Watching Space Charge Build Up in an Organic Solar Cell

et al. 2020

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“…As we all know, the fluctuation of energy band is easy to form traps and leads to the recombination of carriers, which is detrimental to the device performance. Furthermore, based on drift-diffusion model, the effect of band fluctuation is introduced into potential term (Scheunemann et al, 2019;Wang et al, 2019;Xiao et al, 2020). The carrier concentration distribution is calculated ( Figure 6E).…”

Section: Film-depth-dependent Optical and Electronic Propertiesmentioning

confidence: 99%

In situ Measuring Film-Depth-Dependent Light Absorption Spectra for Organic Photovoltaics

et al. 2020

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Organic donor-acceptor bulk heterojunction are attracting wide interests for solar cell applications due to solution processability, mechanical flexibility, and low cost. The photovoltaic performance of such thin film is strongly dependent on vertical phase separation of each component. Although film-depth-dependent light absorption spectra measured by non-in situ methods have been used to investigate the film-depth profiling of organic semiconducting thin films, the in situ measurement is still not well-resolved. In this work, we propose an in situ measurement method in combination with a self-developed in situ instrument, which integrates a capacitive coupled plasma generator, a light source, and a spectrometer. This in situ method and instrument are easily accessible and easily equipped in laboratories of the organic electronics, which could be used to conveniently investigate the film-depth-dependent optical and electronic properties.

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“…[ 43,57 ] Also, a light‐intensity dependent space‐charge region has been observed for asymmetric mobilities. [ 39,58–60 ] However, in the case of asymmetric mobilities the space charge builds up at the contact where the less mobile charge carriers are extracted. [ 39,58,59 ] In contrast, Wu et al.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…[ 39,58–60 ] However, in the case of asymmetric mobilities the space charge builds up at the contact where the less mobile charge carriers are extracted. [ 39,58,59 ] In contrast, Wu et al. noted that the space‐charge region in the absence of asymmetric mobilities but presence of energetic disorder builds up at the contact opposite to the illuminated surface.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

The Influence of Photo‐Induced Space Charge and Energetic Disorder on the Indoor and Outdoor Performance of Organic Solar Cells

Beuel

Hartnagel

Kirchartz

2021

Advcd Theory and Sims

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Apart from traditional large‐scale outdoor application, organic solar cells are also of interest for powering small, off‐grid electronic devices indoors. For operation under the low light intensities that are typical for indoor application, a high shunt resistance is required calling for thick active layers in industrial processing to ensure maximum coverage. However, the thickness of an organic solar cell based on energetically disordered semiconductors is limited by space‐charge effects from charged shallow defects under nonuniform generation. While other sources of space charge such as doping and asymmetric transport have been extensively discussed in previous studies, this work offers a theoretical analysis of this photo‐induced space charge in shallow defects and visualizes how the space charge builds up with increasing light intensity with drift‐diffusion simulations. It is shown that the effect particularly deteriorates the performance of an organic solar cell with high active‐layer thickness and substantial energetic disorder. However, the simulations reveal that solar cells are less sensitive to these parameters under low light intensities due to a reduced density of photo‐induced space charge. Therefore, a wider range of material systems and absorber thicknesses can be viable for indoor applications than one may initially expect from testing under 1 sun illumination.

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Effect of Imbalanced Charge Transport on the Interplay of Surface and Bulk Recombination in Organic Solar Cells

Cited by 24 publications

References 41 publications

Watching Space Charge Build Up in an Organic Solar Cell

Watching Space Charge Build Up in an Organic Solar Cell

In situ Measuring Film-Depth-Dependent Light Absorption Spectra for Organic Photovoltaics

The Influence of Photo‐Induced Space Charge and Energetic Disorder on the Indoor and Outdoor Performance of Organic Solar Cells

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