Impact of Bimolecular Recombination on the Fill Factor of Fullerene and Nonfullerene-Based Solar Cells: A Comparative Study of Charge Generation and Extraction

Hosseini, Seyed Mehrdad; Roland, Steffen; Kurpiers, Jona; Chen, Zhiming; Zhang, Kai; Huang, Fei; Armin, Ardalan; Neher, Dieter; Shoaee, Safa

doi:10.1021/acs.jpcc.8b11669

Cited by 23 publications

(28 citation statements)

References 38 publications

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“…Both techniques have been extensively used to examine timedependent and steady state recombination properties for a wide range of materials, revealing important information on the rate and order of recombination. [29][30][31][32][33][34] The accuracy of these results was confirmed by drift-diffusion simulations of the transient and steady state photocurrents. 28,35 However, the analysis of the TDCF and BACE photocurrent data relies on a number of simplified assumptions.…”

Section: Introductionmentioning

confidence: 53%

Reliability of charge carrier recombination data determined with charge extraction methods

Kniepert

Paulke

Perdigón‐Toro

et al. 2019

Journal of Applied Physics

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Section: Introductionmentioning

confidence: 53%

Reliability of charge carrier recombination data determined with charge extraction methods

Kniepert

Paulke

Perdigón‐Toro

et al. 2019

Journal of Applied Physics

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“…Unfortunately, only few studies concerned the interplay between free carrier generation and motion in NFA-based blends, [51][52][53] and even fewer included the measurement of energetic disorder [47,50,54]. These studies yielded a fairly wide spread of mobilities and recombination coefficients even for the same material combination, which may in part be related to the details of the molecular structure (e.g.…”

Section: Energetic Disorder (Mev)mentioning

confidence: 99%

General Rules for the Impact of Energetic Disorder and Mobility on Nongeminate Recombination in Phase-Separated Organic Solar Cells

et al. 2021

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State of the art organic solar cells exhibit power conversion efficiencies of 18 % and above.These devices benefit from a significant suppression of free charge recombination with regard to the Langevin-limit of charge encounter in a homogeneous medium. It has been recognized that the main cause of suppressed free charge recombination is the reformation and 2 resplitting of charge transfer states at the interface between donor and acceptor domains.Here, we use kinetic Monte Carlo simulations to understand the interplay between free charge motion and recombination in an energetically-disordered phase-separated donoracceptor blend. We identify conditions under which recombination is encounter-dominated and resplitting-dominated. In the latter regime, the non-geminate recombination coefficient becomes independent of the attempt-to-hop frequency, and for a given disorder, independent of charge carrier mobility. Our simulations show that free charge encounter in the phase-separated disordered blend is determined by the average mobility of all carriers, while CT reformation and resplitting involves mostly states near the transport energy. As a consequence, charge encounter is more affected by increased disorder than the resplitting of the CT state. As a consequence, the larger is the energetic disorder, the stronger will 𝐶𝑇resplitting suppress non-geminate recombination versus the Langevin-limit. These findings have important implications for the understanding of suppressed recombination in solar cells with non-fullerene acceptors which are known to exhibit lower energetic disorder than fullerenes.

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“…Typically, OSCs thicker than 100 nm mostly suffer from reduced FFs with only a handful of exceptions. [3][4][5][6][7][8] While it is now well established that, for the NFA systems, charge generation is very efficient, [9][10][11][12][13] the loss in FF is primarily dictated by a competition between charge carrier extraction and non-geminate recombination.…”

Section: Introductionmentioning

confidence: 99%

Putting Order into PM6:Y6 Solar Cells to Reduce the Langevin Recombination in 400 nm Thick Junction

et al. 2020

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Increasing the active layer thickness without sacrificing the power conversion efficiency (PCE) is one of the great challenges faced by organic solar cells (OSCs) for commercialization. Recently, PM6:Y6 as an OSC based on a non‐fullerene acceptor (NFA) has excited the community because of its PCE reaching as high as 15.9%; however, by increasing the thickness, the PCE drops due to the reduction of the fill factor (FF). This drop is attributed to change in mobility ratio with increasing thickness. Furthermore, this work demonstrates that by regulating the packing and the crystallinity of the donor and the acceptor, through volumetric content of chloronaphthalene (CN) as a solvent additive, one can improve the FF of a thick PM6:Y6 device (≈400 nm) from 58% to 68% (PCE enhances from 12.2% to 14.4%). The data indicate that the origin of this enhancement is the reduction of the structural and energetic disorders in the thick device with 1.5% CN compared with 0.5% CN. This correlates with improved electron and hole mobilities and a 50% suppressed bimolecular recombination, such that the non‐Langevin reduction factor is 180 times. This work reveals the role of disorder on the charge extraction and bimolecular recombination of NFA‐based OSCs.

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Impact of Bimolecular Recombination on the Fill Factor of Fullerene and Nonfullerene-Based Solar Cells: A Comparative Study of Charge Generation and Extraction

Cited by 23 publications

References 38 publications

Reliability of charge carrier recombination data determined with charge extraction methods

Reliability of charge carrier recombination data determined with charge extraction methods

General Rules for the Impact of Energetic Disorder and Mobility on Nongeminate Recombination in Phase-Separated Organic Solar Cells

Putting Order into PM6:Y6 Solar Cells to Reduce the Langevin Recombination in 400 nm Thick Junction

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