Enhancing performance of non-fullerene organic solar cells via side chain engineering of fused-ring electron acceptors

Yan, Cenqi; Wu, Yang; Wang, Jiayu; Li, Rong; Cheng, Pei; Bai, Huaiyong; Zhan, Zhiqiang; Ma, Wei; Zhan, Xiaowei

doi:10.1016/j.dyepig.2016.12.065

Cited by 49 publications

(25 citation statements)

References 55 publications

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“…The alkyl side chains on thiophene π‐bridge in small molecule acceptors IEIC series exert the effects on the morphology . The IEIC‐1‐, IEIC‐2‐, IEIC‐3‐, and IEIC‐based devices afford the best PCE of 3.9%, 5.4%, 7.4%, and 6.0%, respectively.…”

Section: Methods To Control Morphologymentioning

confidence: 99%

Morphology Control in Organic Solar Cells

Zhao

Wang

Zhan

2018

Advanced Energy Materials

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501

394

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the working mechanism includes four key steps (as shown in Figure 1): (1) light absorption and Frenkel exciton generation; (2) exciton diffusion to the D/A interface; (3) exciton dissociation into free charge carrier; (4) charge transport and collection. Each step is very important and could become a bottleneck leading to an inferior performance of OSCs. The second and forth steps are dominated by the morphology of the active layer. Since the Frenkel excitons are tightly bounded by Coulombic force, the lifetime of exciton is limited and its diffusion length is only 5-14 nm. [8][9][10] As a result, the domain size should be confined in 5-30 nm to ensure excitons reach D/A interfacial zone and then dissociate into free charge carriers efficiently. On the other hand, high domain purity and fine bicontinuous interpenetrating network nanostructure are also necessary to enable the charge carriers transfer to the electrodes quickly and reduce the bimolecular recombination.The PCE is the overall parameter to evaluate the performance of OSCs, which is the product of open-circuit voltage (V OC ), short-circuit current density (J SC ), and fill factor (FF). Since V OC is proportional to the difference of the highest occupied molecular orbital energy level of the donor and the lowest unoccupied molecular orbital energy level of the acceptor, [11][12][13] the V OC is mainly determined by the donor and acceptor materials. However, V OC is also related to the morphology of the active layer, such as D/A interface area, microstructure, crystallinity and so on. [14] The J SC is dominated by the whole photoelectric conversion process, namely exciton generation, diffusion and dissociation, and charge transport and collection. Among them, efficient exciton diffusion and dissociation, and charge transport strongly depend on the fine morphology of the active layer. [15] FF represents the diode characteristic of the device and is bound up with the charge transport and recombination in the active layer. The fast charge transport and low charge recombination also mainly depend on the morphology, such as crystallinity, molecular orientation, domain purity, vertical phase separation, etc. [15] Therefore, the ideal morphology of the active layer is the crucial factor to achieve high-performance OSCs.The nanomorphology of the active layer is affected by various factors, such as the D/A properties (solubility, crystallinity, miscibility, etc.), film processing, device configuration, and so on. There are only several successful as-cast films affording satisfactory morphology and performance [16][17][18] since it is very hard to obtain ideal morphology and good performance just depending energy and present some advantages, such as low cost, light weight, flexibility, semitransparency, and roll-to-roll large-area fabrication. Due to the short diffusion length of exciton (≈10 nm) in organic semiconductor materials, the ideal nanoscale phase separation in the active layer is one of the crucial factors for achieving efficient exciton dissociation an...

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Section: Methods To Control Morphologymentioning

confidence: 99%

Morphology Control in Organic Solar Cells

Zhao

Wang

Zhan

2018

Advanced Energy Materials

Self Cite

501

394

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“…[ 4 ] In fact, the breakthrough of A‐D‐A type non‐fullerene acceptors are the key to the leap in device PCE. [ 5 ] Through donor−acceptor structure modifications, [ 6 ] functional group substitution, [ 5c ] and side‐chain engineering, [ 7 ] various high‐performance NFAs were developed and studied. DC‐IDT2T was first reported by Zhan et al.…”

Section: Introductionmentioning

confidence: 99%

Simultaneously Achieving Highly Efficient and Stable Polymer:Non‐Fullerene Solar Cells Enabled By Molecular Structure Optimization and Surface Passivation

Liu

Lin

et al. 2022

Advanced Science

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Dedicated to Professor Baowen Zhang on the occasion of her 80th birthday. Despite the tremendous efforts in developing non-fullerene acceptor (NFA) for polymer solar cells (PSCs), only few researches are done on studying the NFA molecular structure dependent stability of PSCs, and long-term stable PSCs are only reported for the cells with low efficiency. Herein, the authors compare the stability of inverted PM6:NFA solar cells using ITIC, IT-4F, Y6, and N3 as the NFA, and a decay rate order of IT-4F > Y6 ≈ N3 > ITIC is measured. Quantum chemical calculations reveal that fluorine substitution weakens the C═C bond and enhances the interaction between NFA and ZnO, whereas the 𝜷-alkyl chains on the thiophene unit next to the C═C linker blocks the attacking of hydroxyl radicals onto the C═C bonds. Knowing this, the authors choose a bulky alkyl side chain containing molecule (named L8-BO) as the acceptor, which shows slower photo bleaching and performance decay rates. A combination of ZnO surface passivation with phenylethanethiol (PET) yields a high efficiency of 17% and an estimated long T 80 and Ts 80 of 5140 and 6170 h, respectively. The results indicate functionalization of the 𝜷-position of the thiophene unit is an effective way to improve device stability of the NFA.

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“…Side‐chain engineering on π bridges also alters molecular properties. With increasing length of alkyl side chains on the π bridges of IEIC1, IEIC2, [ 90 ] IEIC3 [ 90 ] and IEIC [ 24 ] (Figure 8) show gradually down‐shifted HOMO and up‐shifted LUMO energy levels due to increased steric hindrance. When blended with PTB7‐Th, IEIC3‐based blend shows ideal domain size, narrow distribution of domain spacing and relatively higher domain purity, thus the highest J SC and FF.…”

Section: Fused‐ring Electron Acceptorsmentioning

confidence: 99%

“…The devices based on IEIC1, IEIC2, IEIC3 and IEIC show PCEs of 3.9%, 5.4%, 7.4% and 6.0%, respectively. [ 90 ] Introducing sulfur or oxygen atoms into the π‐bridge side chains can construct NIR‐absorbing FREAs. ITIC‐Th‐S and ITIC‐Th‐O (Figure 8) show narrow bandgaps of 1.45 eV and 1.40 eV, respectively, which can be used as NIR third components to enhance light harvesting of FTAZ:IDIC binary blend.…”

Section: Fused‐ring Electron Acceptorsmentioning

confidence: 99%

From Perylene Diimide Polymers to Fused‐Ring Electron Acceptors: A 15‐Year Exploration Journey of Nonfullerene Acceptors

Wang

Zhan

2022

Chin. J. Chem.

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Comprehensive Summary Fullerene derivatives are classic electron acceptor materials for organic solar cells (OSCs) but possess some intrinsic drawbacks such as weak visible light absorption, limited optoelectronic property tunability, difficult purification and photochemical/morphological instability. Fullerene acceptors are a bottleneck restricting further development of this field. Our group pioneered the exploration of novel nonfullerene acceptors in China in 2006, and initiated the research of two representative acceptor systems, rylene diimide polymer and fused‐ring electron acceptor (FREA). FREA breaks the theoretical efficiency limit of fullerene‐based OSCs (~13%) and promotes the whole field to an unprecedented prosperity with efficiency of 20%, heralding a nonfullerene era for OSCs. In this review, we revisit 15‐year nonfullerene exploration journey, summarize the design principles, molecular engineering strategies, physical mechanisms and device applications of these two nonfullerene acceptor systems, and propose some possible research topics in the near future. What is the most favorite and original chemistry developed in your research group? Fused‐ring electron acceptor for photovoltaics. How do you get into this specific field? Could you please share some experiences with our readers? In 2006 when I came back to ICCAS from USA and started my independent academic career, I was interested in organic photovoltaics (OPV) which I had never touched before since I believed it is useful and should have a bright future. OPV converts renewable solar energy to clean electricity through photovoltaic effect. The active layer in OPV device consists of electron donor and electron acceptor. Although fullerenes were prevailing acceptor materials in OPV at that time, I doubted if this choice is correct considering their fatal flaws such as weak absorption. I was curious about why no research groups in China explored fullerene alternatives before 2006. In 2006 our group initiated the nonfullerene OPV research of China. In 2015 we invented the milestone molecule ITIC and pioneered fused‐ring electron acceptor (FREA). Around 300 research groups in >20 countries have utilized the FREA to fabricate high‐efficiency OPV devices with champion efficiency of >20%. The FREA has subverted previously predominant fullerenes, and is inaugurating a new era of the OPV field. How do you supervise your students? I expect that my students should have some essential personalities such as curiosity, creativity, devotion, persistence and diligence. I encourage them to do original, unique and leading research. I endow them with cheerful academic atmosphere such as self‐motivation, open‐mindedness and cross‐cooperation. I would like to provide them with warm human solicitude when they need help or suffer from bitterness. What is the most important personality for scientific research? Curiosity; uniqueness; persistence.

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Enhancing performance of non-fullerene organic solar cells via side chain engineering of fused-ring electron acceptors

Cited by 49 publications

References 55 publications

Morphology Control in Organic Solar Cells

Morphology Control in Organic Solar Cells

Simultaneously Achieving Highly Efficient and Stable Polymer:Non‐Fullerene Solar Cells Enabled By Molecular Structure Optimization and Surface Passivation

From Perylene Diimide Polymers to Fused‐Ring Electron Acceptors: A 15‐Year Exploration Journey of Nonfullerene Acceptors

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