Highly efficient organic solar cells with superior deformability enabled by diluting the small molecule acceptor content

Zhu, Qinglian; Xue, Jingwei; Zhao, Heng; Lin, Baojun; Bi, Zhaozhao; Seibt, Susanne; Zhou, Ke; Ma, Wei

doi:10.1039/d2ta00959e

Cited by 15 publications

(13 citation statements)

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“…The peak location evolution of both two films can be divided into three stages. [ 36 ] A test interval (0.5 s) is adopted here to investigate the film‐drying kinetics of the active layer. If the peak location change of each interval is larger than 1 nm and this tendency does not change anymore, we define that a stage is finished, and the film drying process comes into the following stage.…”

Section: Resultsmentioning

confidence: 99%

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In Situ Absorption Characterization Guided Slot‐Die‐Coated High‐Performance Large‐Area Flexible Organic Solar Cells and Modules

Shen

Zhang

et al. 2023

Advanced Materials

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The PCEs of small-area single junction OSCs have reached over 19%, providing an essential foundation for scaling up. [16][17][18] However, these devices with an effective area smaller than 0.1 cm 2 are usually fabricated by the spin-coating method on glassindium tin oxide (ITO) substrates, which limits the further upscale continuous production due to the associated uneven linear speed. Large-area coating methods, such as spray coating, [16] blade coating, [17][18][19] slot-die coating, [20][21][22] inkjet printing, [23] etc., are widely used in the scalable fabrication of large-area OSCs. Due to its advantages of easy operation, low material waste, and high throughput, the slot-die coating process is considered one of the most promising approaches in the field of largearea OSCs and has the potential for further roll-to-roll (R2R) production. [24][25][26][27][28] Recently, many studies revealed that the solvent drying process in the slot-die coating is much slower than that in spin coating, leading to a significant change in the nanoscale morphology of the photoactive layers. [29] Various efforts have been devoted to optimizing the slot-die coating methodology for fabricating high-efficiency OSCs. Early in 2014, Zhan et al. focused on the drying mechanism in the spin-coating and roll-coated methods by comparing the amount of additive, demonstrating the importance of the individual optimization approach in the large-area coating process. [30] By synergistic optimization of slot-die coating conditions, our group successfully acquired high-efficiency flexible devices, which maintain over 98% PCE of the small-area rigid devices. [31] Besides the coating condition optimization, tremendous efforts have been made to investigate the aggregation during the coating process. Ma et al. revealed that processing conditions could affect the phase-separation kinetics of donors and acceptors in the active layer, such as coating temperature and solution temperature. [32,33] Molecular aggregation ability significantly influences film formation kinetics of the active layer, while its influence on slot-die coating fabrication has seldom been investigated. Recently, we developed two acceptors with low reorganization energy, i.e., Qx-1 and Qx-2, and the spin-coated small-area devices of PM6:Qx-1 and PM6:Qx-2 fabricated using chloroform showed similar device performance (≈18%) due to their similar molecular structure. [34] Slot-die coating is recognized as the most compatible method for the roll-toroll (R2R) processing of large-area flexible organic solar cells (OSCs). However, the photovoltaic performance of large-area flexible OSC lags significantly behind that of traditional spin-coating devices. In this work, two acceptors, Qx-1 and Qx-2, show quite different film-formation kinetics in the slot-die coating process. In situ absorption spectroscopy indicates that the excessive crystallinity of Qx-2 provides early phase separation and early aggregation, resulting in oversized crystal domains. Consequently, the PM6:Qx-1-based 1 cm 2 flex...

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Section: Resultsmentioning

confidence: 99%

“…The peak location evolution of both two films can be divided into three stages. [36] A test interval (0.5 s) is adopted here to investigate the film-drying kinetics of the active layer. If the a) The device areas are 0.0256 cm 2 ; b) The device areas are 1 cm 2 .…”

Section: Formation Kinetics Of Slot-die-coated Filmsmentioning

confidence: 99%

In Situ Absorption Characterization Guided Slot‐Die‐Coated High‐Performance Large‐Area Flexible Organic Solar Cells and Modules

Shen

Zhang

et al. 2023

Advanced Materials

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“…Many strategies have been used to improve their mechanical properties, including physically mixed insulating polymers (PS, PDMS, SEBS, etc. ), covalently linked insulating polymer chains into the backbones or side chains, ternary OSCs by using the third conjugated components, and adjusting the amorphous/crystalline nature. − These methods can indeed help to improve the COS, but there are still some issues. For example, the addition of insulating polymers will dilute the conjugated components, and the enhancement of the amorphous region will lower charge carrier mobilities and PCEs in OSCs. , It will be an important task to develop conjugated polymers with excellent mechanical properties and meanwhile provide high performance in OSCs.…”

Section: Introductionmentioning

confidence: 99%

Revisiting Conjugated Polymers with Long-Branched Alkyl Chains: High Molecular Weight, Excellent Mechanical Properties, and Low Voltage Losses

et al. 2022

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High-molecular-weight conjugated polymers exhibit excellent mechanical properties due to long-chain entanglement, but it is challenging to increase molecular weight since conjugated polymers with rigid backbones show low solubility and tend to be precipitated during polymerization. In this work, we have successfully obtained high-molecular-weight polymers through the introduction of long-branched alkyl chains and optimization of polymerization conditions. Three conjugated polymers with long 2-octyldodecyl side units were obtained with number-average molecular weights (M n s) of 38.8 kDa (OD-PM6_L), 81.2 kDa (OD-PM6_M), and 178.3 kDa (OD-PM6_H), while the conjugated polymer PM6 with short 2-ethylhexyl units showed an M n of 43.8 kDa. The branched side units and molecular weight have a significant influence on the mechanical properties, in which the elastic ranges and the crack-onset strains were enhanced to >20% and >170% in OD-PM6_H thin films. In addition, due to the suppressed non-nonradiative recombination via increasing the donor− acceptor spacings, organic photovoltaic devices based on OD-PM6_H showed an efficiency of over 13% with low voltage loss. These results demonstrate that introducing longer side units into conjugated polymers provides the opportunity to realize high molecular weight, resulting in excellent mechanical properties and high efficiencies in organic solar cells toward flexible applications.

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“…In addition, crystallinity is an important parameter to be considered for morphology optimization . Using a highly crystalline small molecule donor as a third component improves the overall crystallinity of the ternary blend and does not produce excessive aggregation, thus mixing the polymer donor with the small molecule donor provides a way to obtain optimal morphology. , For example, Zhang et al added a small molecule (SM) donor BPR-SCl with deep highest occupied molecular orbital (HOMO) energy level and strong crystallinity to the PM6:BTP-eC9 system to enhance the crystallinity of the active layer, which slightly reduced the phase separation to promote exciton separation, enhance the hole mobility, and yielding a high efficiency of 18.02%. Zhao et al reported a TOSC based on PM6:TTBT-R:Y6, designed asymmetric molecule TTBT-R with high crystallinity and good compatibility with PM6.…”

Section: Introductionmentioning

confidence: 99%

Efficient and Stable Ternary Organic Solar Cells Using Liquid Crystal Small Molecules with Multiple Synergies

Wen

Lin

et al. 2022

ACS Appl. Energy Mater.

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A liquid crystal small molecule donor BTR-Cl, which has strong self-assembly and crystallinity, is used as the third component to construct nonfullerenes ternary solar cells together with a broad-band donor polymer D18-Cl and a low-band acceptor N3. The introduction of BTR-Cl enhances the morphology, exciton dissociation, and charge mobility of the ternary blends, improves the short-circuit current density and fill factor, and results in an efficiency of up to 17.92%. Further results show that BTR-Cl acts as an energy level mediator, fluorescence resonance energy transfer and charge transfer intermediary, and morphology modifier in ternary blends. They work synergistically in ternary blends to optimize the electrical and morphological properties, resulting in enhanced photovoltaic performance and improved stability and detection performance. It brings vitality to the field of organic solar cells (OSCs) and organic photodetectors (OPDs) research.

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Highly efficient organic solar cells with superior deformability enabled by diluting the small molecule acceptor content

Abstract: Developing efficient organic solar cells (OSCs) with strong mechanical deformability is urgent to be addressed to promise their operational reliability in wearable electronics. However, it is challenging to achieve mechanical...

Cited by 15 publications

References 58 publications

In Situ Absorption Characterization Guided Slot‐Die‐Coated High‐Performance Large‐Area Flexible Organic Solar Cells and Modules

In Situ Absorption Characterization Guided Slot‐Die‐Coated High‐Performance Large‐Area Flexible Organic Solar Cells and Modules

Revisiting Conjugated Polymers with Long-Branched Alkyl Chains: High Molecular Weight, Excellent Mechanical Properties, and Low Voltage Losses

Efficient and Stable Ternary Organic Solar Cells Using Liquid Crystal Small Molecules with Multiple Synergies

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