Extraordinarily long diffusion length in PM6:Y6 organic solar cells

Tokmoldin, Nurlan; Hosseini, Seyed Mehrdad; Raoufi, Meysam; Phuong, Le Quang; Sandberg, Oskar J.; Guan, Huilan; Zou, Yingping; Neher, Dieter; Shoaee, Safa

doi:10.1039/d0ta03016c

Cited by 90 publications

(78 citation statements)

References 31 publications

(42 reference statements)

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“…Figure 1b showcases simulated J–V curves for the 400 nm device in three different scenarios: 1) parameters based on experimental data; 2) when the hole mobility is hypothesized to be four times higher than that measured; and 3) when k 2 is reduced by 50% and the hole mobility is also increased by a factor of 4. As demonstrated in Figure 1b, lowering k 2 by twofold to reach reduced‐Langevin recombination and a fourfold higher hole mobility, compared with what we have previously published for a thick PM6:Y6 system, [ 9,22 ] as input parameters, generates an FF in the range of 65–70% (see Table S1 and Figure S1, Supporting Information, for details).…”

Section: Resultssupporting

confidence: 69%

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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Section: Resultssupporting

confidence: 69%

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

et al. 2020

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“…The diffusion length of carriers in 100‐nm PM6:Y6 devices was recently reported to be comparable with the thickness of the active layer. [ 44 ] When the transporting layers which reduce the diffusion of the minority carriers towards the wrong electrodes are removed, the long diffusion lengths of carriers might enhance surface recombination. [ 45 ] These results are reproduced by corresponding simulations, shown by the solid black curves in Figure 3b, for a PM6:Y6 device with nonohmic contacts, exhibiting considerable injection barriers for holes at the anode and electrons at the cathode contacts, respectively.…”

Section: Resultsmentioning

confidence: 99%

Quantifying Quasi‐Fermi Level Splitting and Open‐Circuit Voltage Losses in Highly Efficient Nonfullerene Organic Solar Cells

et al. 2020

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The power conversion efficiency (PCE) of state‐of‐the‐art organic solar cells is still limited by significant open‐circuit voltage (VOC) losses, partly due to the excitonic nature of organic materials and partly due to ill‐designed architectures. Thus, quantifying different contributions of the VOC losses is of importance to enable further improvements in the performance of organic solar cells. Herein, the spectroscopic and semiconductor device physics approaches are combined to identify and quantify losses from surface recombination and bulk recombination. Several state‐of‐the‐art systems that demonstrate different VOC losses in their performance are presented. By evaluating the quasi‐Fermi level splitting (QFLS) and the VOC as a function of the excitation fluence in nonfullerene‐based PM6:Y6, PM6:Y11, and fullerene‐based PPDT2FBT:PCBM devices with different architectures, the voltage losses due to different recombination processes occurring in the active layers, the transport layers, and at the interfaces are assessed. It is found that surface recombination at interfaces in the studied solar cells is negligible, and thus, suppressing the non‐radiative recombination in the active layers is the key factor to enhance the PCE of these devices. This study provides a universal tool to explain and further improve the performance of recently demonstrated high‐open‐circuit‐voltage organic solar cells.

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“…To achieve high performance in an OSC, it is critical to have proper film morphology in its photoactive layer in order to maintain a balance between exciton dissociation and charge transport. In the past few years, bulk heterojunction (BHJ) architecture has gained great success in OSC based on polymeric donors and fullerene-derived acceptors 4 , which circumvents the short exciton diffusion length in polymer donor materials (typically 5–10 nm) 5 , 6 by providing an interpenetrating donor/acceptor (D/A) network for electron- and hole-transport 7 . This approach has successfully increased the short-circuit current density ( J SC ) in OSCs.…”

Section: Introductionmentioning

confidence: 99%

Pseudo-bilayer architecture enables high-performance organic solar cells with enhanced exciton diffusion length

et al. 2021

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Solution-processed organic solar cells (OSCs) are a promising candidate for next-generation photovoltaic technologies. However, the short exciton diffusion length of the bulk heterojunction active layer in OSCs strongly hampers the full potential to be realized in these bulk heterojunction OSCs. Herein, we report high-performance OSCs with a pseudo-bilayer architecture, which possesses longer exciton diffusion length benefited from higher film crystallinity. This feature ensures the synergistic advantages of efficient exciton dissociation and charge transport in OSCs with pseudo-bilayer architecture, enabling a higher power conversion efficiency (17.42%) to be achieved compared to those with bulk heterojunction architecture (16.44%) due to higher short-circuit current density and fill factor. A certified efficiency of 16.31% is also achieved for the ternary OSC with a pseudo-bilayer active layer. Our results demonstrate the excellent potential for pseudo-bilayer architecture to be used for future OSC applications.

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Extraordinarily long diffusion length in PM6:Y6 organic solar cells

Abstract: Simulated energy band diagrams of thin and thick PM6:Y6 devices.

Cited by 90 publications

References 31 publications

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

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

Quantifying Quasi‐Fermi Level Splitting and Open‐Circuit Voltage Losses in Highly Efficient Nonfullerene Organic Solar Cells

Pseudo-bilayer architecture enables high-performance organic solar cells with enhanced exciton diffusion length

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