Higher Mobility and Carrier Lifetimes in Solution‐Processable Small‐Molecule Ternary Solar Cells with 11% Efficiency

Liang, Ru‐Ze; Zhang, Yiming; Savikhin, Victoria; Babics, Maxime; Kan, Zhipeng; Wohlfahrt, Markus; Wehbe, Nimer; Liu, Shengjian; Duan, Tainan; Toney, Michael F.; Laquai, Frédéric; Beaujuge, Pierre M.

doi:10.1002/aenm.201802836

Cited by 71 publications

(57 citation statements)

References 69 publications

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“…Here, PB D rises due to hole transfer from ICC6 to DR3. We note that charge generation is slower than in the binary DR3:ICC6 blend due to larger ICC6 domains, as indicated by scanning tunneling electron microscopy (STEM) imaging coupled with electron energy‐loss spectroscopy (EELS) reported earlier by Liang et al This is also in line with the increased PL lifetime seen in ternary blends compared to binary blends (see Table ).…”

Section: Resultssupporting

confidence: 85%

“…The addition of PC 71 BM not only enhances the EQE in the 350–450 nm region, but surprisingly also improves the EQE across the entire absorption range of the ternary blend. This improvement is a consequence of the improved charge carrier mobility in ICC6 due to increased crystallinity of ICC6 upon blending with PC 71 BM, as has recently been demonstrated by Liang et al However, excess of PC 71 BM deteriorates the EQE due to morphological changes and decreased crystallinity . In line with the higher EQE, the internal quantum efficiency (IQE) increases, reaching >90% for the fully optimized ternary devices.…”

Section: Resultsmentioning

confidence: 64%

“…Figure e compares the current density–voltage ( J–V ) curves for binary and ternary solar cells that were optimized by solvent vapor annealing (SVA). Details of the SVA optimization are reported elsewhere . The device figures of merit are shown in Table 1 .…”

Section: Resultsmentioning

confidence: 99%

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Impact of Fullerene on the Photophysics of Ternary Small Molecule Organic Solar Cells

Karuthedath

Firdaus

Liang

et al. 2019

Advanced Energy Materials

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currently at the forefront of efficient OSCs and outperform binary systems in terms of power conversion efficiency (PCE), largely due to improved light absorption and mor phology, especially if novel nonfullerene acceptors are employed. [2] Ternary solar cells use a single (ternary blend) photo active layer for photon harvesting and thus are less challenging and costly to realize, compared to tandem solar cells, [3] which have the potential of even higher efficien cies. [4] However, in TSCs, the third compo nent of the blend not only improves light harvesting, but also plays an active role in the photophysical processes including exciton and chargecarrier dynamics and can, in fact, also influence the blend's morphology. [5] This is of critical impor tance in small moleculebased devices, where intermolecular charge transport dominates. [6] Often, the third component in ter nary solar cells enhances the PCE by improving the shortcircuit current (J SC ) [5c] and opencircuit voltage (V OC ), which both can be tuned by the donor/ acceptor composition. [2d,5b] The chal lenge here is, however, to improve all device parameters, while maintaining or increasing the fill factor (FF) of the ternary organic solar cell. [7] Here, we study the photophysics of such a highperformance allsmallmolecule ternary solar cell com posed of DR3TBDTT (DR3) [8] as an electron donor in combi nation with a nonfullerene smallmolecule acceptor, namely ICC6IDTIC (or ICC6) [9] and PC 71 BM as the third component, shown to enhance the device performance. The fully opti mized ternary devices (1:1:0.4 wt%, DR3:ICC6:PC 71 BM) yield an average PCE of 10.8% with a FF of 72%, V OC of 0.87 V, and J SC of 16.3 mA cm −2 . Using picosecond-nanosecond (ps-ns) transient absorption (TA) spectroscopy, we selectively excite each component of the blend and probe the processes following photoexcitation. We find that excitation of PC 71 BM molecules results in fast singlet energy transfer to ICC6, sub sequently followed by hole transfer to DR3. We confirm this observation by TA and timeresolved photoluminescence (TRPL) spectroscopy on binary blends of PC 71 BM:ICC6, showing fast energy transfer from PC 71 BM to ICC6. Our TA studies demon strate that the increased external quantum efficiency (EQE) of the ternary blend is due to higher mobility of charge carriers in Ternary organic solar cells (OSCs) are among the best-performing organic photovoltaic devices to date, largely due to the recent development of nonfullerene acceptors. However, fullerene molecules still play an important role in ternary OSC systems, since, for reasons not well understood, they often improve the device performance, despite their lack of absorption. Here, the photophysics of a prototypical ternary small-molecule OSC blend composed of the donor DR3, the nonfullerene acceptor ICC6, and the fullerene derivative PC 71 BM is studied by ultrafast spectroscopy. Surprisingly, it is found that after excitation of PC 71 BM, ultrafast singlet energy transfer to ICC6 competes efficiently with cha...

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Section: Resultssupporting

confidence: 85%

Section: Resultsmentioning

confidence: 64%

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Impact of Fullerene on the Photophysics of Ternary Small Molecule Organic Solar Cells

Karuthedath

Firdaus

Liang

et al. 2019

Advanced Energy Materials

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“…The ternary blend of SBDT‐BDD: IDIC :PC 71 BM exhibited an enhanced PCE of 10.9% due to increased photoabsorption, and optimal morphology led to higher J SC and FF. Beaujuge et al also reported an ASM‐ternary OSC using a blend of DR3TBDTT: IDIC :PC 71 BM exhibiting a high PCE of 10.8% due to low recombination losses …”

Section: Other Aspects Of Frea Oscsmentioning

confidence: 98%

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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“…Recently, combining the advantages of nonfullerene acceptors, ternary solar cells using two NFAs (1D/2NFA) yield over 16% efficiency . However, the active layers of most high‐performance ternary solar cells need extra post‐treatments or solvent additives, which may limit their future applications . Hence, developing ternary solar cells without the need of using these extra treatments is highly desired.…”

Section: Introductionmentioning

confidence: 99%

As‐Cast Ternary Organic Solar Cells Based on an Asymmetric Side‐Chains Featured Acceptor with Reduced Voltage Loss and 14.0% Efficiency

Chen

Kan

et al. 2020

Adv Funct Materials

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A new small‐molecule nonfullerene acceptor based on the benzo[1,2‐b:4,5‐b′]dithiophene (BDT) fused central core with asymmetrical alkoxy and thienyl side chains, namely TOBDT, is designed and synthesized. The alkoxy unit helps narrow the bandgap, and thienyl side chain helps enhance the intermolecular interaction. As a result, TOBDT is suitable to match the deep‐lying highest occupied molecular orbital (HOMO) of polymer donor PM6. Then, a strong crystalline acceptor IDIC is introduced as the third component to fabricate as‐cast nonfullerene ternary devices to achieve absorption and morphology control. Addition of IDIC not only mixes well with TOBDT but modulates the morphology of the blend film, which helps to balance the charge transport properties and reduce the photovoltage loss of ternary devices. All these contribute to synergetic improvement of Jsc, Voc, and fill factor parameters, leading to a power conversion efficiency of 14.0% for the as‐cast fullerene‐free ternary device.

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Higher Mobility and Carrier Lifetimes in Solution‐Processable Small‐Molecule Ternary Solar Cells with 11% Efficiency

Cited by 71 publications

References 69 publications

Impact of Fullerene on the Photophysics of Ternary Small Molecule Organic Solar Cells

Impact of Fullerene on the Photophysics of Ternary Small Molecule Organic Solar Cells

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

As‐Cast Ternary Organic Solar Cells Based on an Asymmetric Side‐Chains Featured Acceptor with Reduced Voltage Loss and 14.0% Efficiency

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