Effect of Core Size on Performance of Fused-Ring Electron Acceptors

Dai, Shuixing; Xiao, Yiqun; Xue, Peiyao; Rech, Jeromy James; Liu, Kuan; Li, Zeyuan; Lu, Xinhui; You, Wei; Zhan, Xiaowei

doi:10.1021/acs.chemmater.8b02222

Cited by 107 publications

(90 citation statements)

References 49 publications

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“…The ternary approach, by introducing a smaller bandgap nonfullerene acceptor as a near infrared (NIR) absorber to increase the device J sc of fullerene‐free binary blended material systems, hereafter named as the “current‐increased” strategy, has received an increasing interest recently . First, homogeneous acceptor phases can be facilely formed due to their structural similarity between the selected two nonfullerene acceptors .…”

Section: Introductionmentioning

confidence: 99%

Ternary Blended Fullerene‐Free Polymer Solar Cells with 16.5% Efficiency Enabled with a Higher‐LUMO‐Level Acceptor to Improve Film Morphology

Tang

et al. 2019

Advanced Energy Materials

223

184

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achieved power conversion efficiencies (PCEs) greater than 15% in singlejunction binary devices. [13,14] However, the performance of the binary system is still largely limited by the material's own properties (narrow absorption, small crystallinity, low charge mobility, strong recombination, etc.). In order to overcome these limitations, the strategy of adding a third component to the binary system, e.g., ternary solar cell approach, has come into being and shown wideranging applicability in improving the solar cell device function. The addition of a structurally similar third component can either extend the absorption range of solar emission spectrum, tune the frontier molecular orbital (FMOs) levels such as through forming homogeneous donor or acceptor phases, [15,16] modulate the active layer's electric property by improving the film morphology, [17][18][19] or tune the acceptor phase optical property, [20] which can promote either the device short-circuit current density (J sc ), or open-circuit voltage (V oc ), or fill factor (FF), and finally, boost power conversion efficiencies with the values reaching over 13% recently. [21][22][23][24][25][26] The ternary approach, by introducing a smaller bandgap nonfullerene acceptor as a near infrared (NIR) absorber to increase the device J sc of fullerene-free binary blended material systems, hereafter named as the "current-increased" Ternary approaches to solar cell design utilizing a small bandgap nonfullerene acceptor as the near infrared absorber to increase the short-circuit current density always decreases the open-circuit voltage. Herein, a highly efficient polymer solar cell with an impressive efficiency of 16.28 ± 0.20% enabled by an effective voltage-increased ternary blended fullerene-free material approach is reported. In this approach, the structural similarity between the host and the higher-LUMO-level guest enables the two acceptors to be synergized, obtaining increased open-circuit voltage and fill factor and a small increase of short-circuit current density. The same beneficial effects are demonstrated by using two host binary systems. The homogeneous fine film morphologies and the π-π stacking patterns of the host blend are well maintained, while larger donor and acceptor phases and increased lamellar crystallinity, increased charge mobilities, and reduced monomolecular recombination can be achieved upon addition of the guest nonfullerene acceptor. The increased charge mobilities and reduced monomolecular recombination not only contribute to the improved fill factor but also enable the best devices to be fabricated with a relatively thicker ternary blended active layer (110 vs 100 nm). This, combined with the absorption from the added guest acceptor, contribute to the increased short-circuit current.

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Section: Introductionmentioning

confidence: 99%

Ternary Blended Fullerene‐Free Polymer Solar Cells with 16.5% Efficiency Enabled with a Higher‐LUMO‐Level Acceptor to Improve Film Morphology

Tang

et al. 2019

Advanced Energy Materials

223

184

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“…Nevertheless, two recent reports suggested that an increasing number of heterocyclic rings beyond 8–9 rings does not further extend the absorption . Besides, FREAs with larger core have similar electrochemical properties suggesting that further increase in the number of rings does not translate into improved efficiency yet adding synthetic complexity.…”

Section: Nfas and Various Aspects Of Freasmentioning

confidence: 96%

“…The nanoscale morphology of the ternary blend found to be like the binary devices with both the FREAs showed excellent compatibility. Zhan and co‐workers also recently utilized a similar strategy to boost the V OC with an addition of the third component with higher LUMO level . A PCE of 12.6% was achieved using a blend of FTAZ: F9IC : F11IC due to efficient charge dissociation and collection enhancing both FF and J SC .…”

Section: Other Aspects Of Frea Oscsmentioning

confidence: 99%

Recent Progress in Molecular Design of Fused Ring Electron Acceptors for Organic Solar Cells

Dey

2019

Small

139

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The quest for sustainable energy sources has led to accelerated growth in research of organic solar cells (OSCs). A solution‐processed bulk‐heterojunction (BHJ) OSC generally contains a donor and expensive fullerene acceptors (FAs). The last 20 years have been devoted by the OSC community to developing donor materials, specifically low bandgap polymers, to complement FAs in BHJs. The current improvement from ≈2.5% in 2013 to 17.3% in 2018 in OSC performance is primarily credited to novel nonfullerene acceptors (NFA), especially fused ring electron acceptors (FREAs). FREAs offer unique advantages over FAs, like broad absorption of solar radiation, and they can be extensively chemically manipulated to tune optoelectronic and morphological properties. Herein, the current status in FREA‐based OSCs is summarized, such as design strategies for both wide and narrow bandgap FREAs for BHJ, all‐small‐molecule OSCs, semi‐transparent OSC, ternary, and tandem solar cells. The photovoltaics parameters for FREAs are summarized and discussed. The focus is on the various FREA structures and their role in optical and morphological tuning. Besides, the advantages and drawbacks of both FAs and NFAs are discussed. Finally, an outlook in the field of FREA‐OSCs for future material design and challenges ahead is provided.

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“…Meanwhile, the D core also plays a key role in adjusting the

E_{normalg}^{opt}

s and energy levels of NFAs. For example, using a strong electron‐donating capacity D core can amplify the intramolecular charge transfer (ICT) effect for a narrow

E_{normalg}^{opt}

. However, such a D core also leads to a high HOMO level, which not only astrict the option of donor material but also limit the increase in V oc .…”

Section: Introductionmentioning

confidence: 99%

A Novel Carbazole‐Based Nonfullerene Acceptor for High‐Efficiency Polymer Solar Cells

et al. 2019

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It is important to tune the energy levels of nonfullerene acceptors (NFAs) to achieve more balanced open‐circuit voltage (Voc) and short‐circuit current density (Jsc) to improve the device performance. Herein, two novel NFAs are designed via fusing fluorene or carbazole with two thieno[3,2‐b]thiophene and end capped with INIC‐2F, namely, 4TFIC‐4F and 4TCIC‐4F, respectively. The impact of the fluorene and carbazole unit on the PSC performance is systematically studied. Compared with 4TFIC‐4F, 4TCIC‐4F exhibits a higher lowest unoccupied molecular orbital (LUMO) energy level of −3.95 eV and a narrower optical bandgap of 1.51 eV owing to the stronger electron‐donating capacity of fused‐carbazole ring core. Consequently, the 4TCIC‐4F device achieves a high power conversion efficiencies (PCE) of 13.02% with a higher Voc of 0.94 V and a larger Jsc of 18.98 mA cm−2, whereas the 4TFIC‐4F device shows a PCE of 11.24%. The PCE of 13.02% is the highest value so far reported with the carbazole‐containing NFAs‐based PSCs. More importantly, the 4TCIC‐4F device shows good film thickness insensitive and long‐term thermal stability. The investigation demonstrates that the fused‐carbazole ring is a superior option to fused‐fluorene ring as electron‐donating core for designing high‐performance NFAs by improving Voc and Jsc simultaneously.

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Effect of Core Size on Performance of Fused-Ring Electron Acceptors

Cited by 107 publications

References 49 publications

Ternary Blended Fullerene‐Free Polymer Solar Cells with 16.5% Efficiency Enabled with a Higher‐LUMO‐Level Acceptor to Improve Film Morphology

Ternary Blended Fullerene‐Free Polymer Solar Cells with 16.5% Efficiency Enabled with a Higher‐LUMO‐Level Acceptor to Improve Film Morphology

Recent Progress in Molecular Design of Fused Ring Electron Acceptors for Organic Solar Cells

A Novel Carbazole‐Based Nonfullerene Acceptor for High‐Efficiency Polymer Solar Cells

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