An end-capped strategy for crystalline polymer donor to improve the photovoltaic performance of non-fullerene solar cells

Zheng, Bing; Yue, Yuchen; Ni, Jianling; Sun, Rui; Min, Jie; Wang, Jingxia; Jiang, Lei; Huo, Lijun

doi:10.1007/s11426-021-1205-5

Cited by 10 publications

(19 citation statements)

References 57 publications

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“…These features proved that the end-capping reagent EBr could react efficiently with Me 3 Sn in high yield and hence reduce the chance of side reactions. Considering the high molecular weight bias by MALDI-TOF-MS, the so-called “polydispersity index (PDI)” of PM6E1 should be much smaller than PM61, and the yield of EDAE was much higher than DADMe 2 according to Figure a. , …”

Section: Resultsmentioning

confidence: 99%

“…Considering the high molecular weight bias by MALDI-TOF-MS, the so-called "polydispersity index (PDI)" of PM6E1 should be much smaller than PM61, and the yield of EDAE was much higher than DADMe 2 according to Figure 1a. 23,59 The yield of end-capping by E estimated from MALDI-TOF-MS (Y MALDI ) and NMR (Y NMR ) was summarized in Table 1. It should be noted that the end-capping yields are rarely mentioned due to the end-caping being low percentage and difficult to measure accurately.…”

Section: Polymer Synthesis and Characterizationmentioning

confidence: 99%

“…Organic solar cells (OSCs) can be flexible, lightweight, colorful, and large-area printing, which attracted extensive attention to increase their photovoltaic performance. , Owing to the development of new materials and device fabrication skills, the best power conversion efficiency (PCE) of single-junction and tandem OSCs have reached over 19 − and 20%, respectively. Generally, OSCs are based on a bulk heterojunction (BHJ) structure formed by a donor–acceptor (D–A) copolymer and small molecule acceptor. − Both the molecular weight and stability of the polymer are vital to determine the photovoltaic performance. − But the conjugated polymers have suffered from batch-to-batch variations, which may be caused by molecular weight control and unreacted end traps. − Nowadays, most of the polymers for OSCs are synthesized by Stille coupling, but the remaining terminal groups (unreacted halogen, trimethyltin, or byproducts) will be left if the polymer has not been end-capped efficiently. − These end sites would disturb the molecular packing, capture charge carriers, induce bad morphology, decrease the crystallinity, and result in poor mobility . For instance, Huo et al decreased the bromine atom percentage by end-capping Soxhlet-purified PM6, which had significant improvement on the photovoltaic performance of non-fullerene solar cells .…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of Crown Ether End-Capped PM6 Copolymers with Tunable Molecular Weight for Organic Solar Cells

Li,

Liu,

Shui

et al. 2023

Macromolecules

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Poly-[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione))] (PM6) is one of the star molecules in organic solar cells (OSCs). However, PM6 has been suffering from molecular weight control and unreacted terminal groups. Thus, synthesizing high-quality polymers without batch-to-batch variations has been challenging for many years. Herein, a one-step protocol of both end-capping and polymerization at the same time was developed to prepare end-capped PM6 with molecular weight controlled by changing the monomer ratio. Specifically, non-end-capped PM67 and a series of PM6En with different molecular weights were synthesized and characterized. Our research findings indicated that (1) these copolymers’ number-average molecular weights (M ns) and weight-average molecular weights (M ws) were measured to be almost linearly increased. Although textbooks have mentioned the nonequivalent ratio monomer strategy to regulate the molecular weight of polymers, the end-capping yield has not been reported in the research of OSCs due to a lack of efficient experiments and instruments to measure the low percentage of end groups in the polymer. (2) Since the selected end-caping reagent 4′-bromobenzo-18-crown-6 (EBr) can be easily distinguished from the PM6 main backbone, we first measured the end-capping yield by both nuclear magnetic resonance (NMR) and matrix-assisted laser desorption/ionization time-of-flight mass spectra (MALDI-TOF-MS). We applied this approach for the first time to synthesize polymers with reasonable end-capping yields (40–97%) for OSCs. (3) Surprisingly, 18-crown-6 can reduce end-group defects, lower the polydispersity index (PDI) of the polymer, and achieve suitable morphology and mobility. As a result, the end-capped PM6E7-based device exhibited the best stability and power conversion efficiency (PCE) compared to those of the other end-capped or non-end-capped polymers. Both the end groups and molecular weight significantly affect the performance of the OSCs. PM6 and other copolymers could be finely tuned by subtly changing the molecular weights or end-cap groups with functional building blocks. Our research will stimulate the development of OSCs and other applications of copolymers.

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Section: Resultsmentioning

confidence: 99%

Section: Polymer Synthesis and Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Synthesis of Crown Ether End-Capped PM6 Copolymers with Tunable Molecular Weight for Organic Solar Cells

Li,

Liu,

Shui

et al. 2023

Macromolecules

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“…During the past two decades, a large number of interdisciplinary approaches have been focused on bulk-heterojunction (BHJ) organic solar cells (OSCs) from both scientific and technological research viewpoints, which have led to remarkable progress and tremendous breakthroughs. [1][2][3][4][5][6] The flexibility, lightness, wearability, biocompatibility, and especially the printability and other advantages of organic solar cells [7][8][9][10] promise unprecedented and innovative applications, while conventional inorganic solar cells are difficult to achieve. To date, under the synergy of molecular structure engineering and device engineering, the PCE of OSCs has exceeded 19%.…”

Section: Introductionmentioning

confidence: 99%

A two-armed skeleton extension strategy for the design of novel spirobifluorene-based small molecule donors

et al. 2023

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“…The “end‐capped” strategy can also achieve the regulation of the aggregated state and miscibility, which are rarely reported in recent years. The PM6TPO, possessing additional end‐capped group with PM6, [ 40 ] is introduced into previous proposed binary system PM6:PY‐IT as the third component. PM6TPO can be referred as “twins” polymer with PM6.…”

Section: Introductionmentioning

confidence: 99%

All‐Polymer Solar Cells with 17% Efficiency Enabled by the “End‐Capped” Ternary Strategy

Yue

Zheng

et al. 2022

Advanced Science

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Recently, all‐polymer solar cells (all‐PSCs) have received increasing attention and made tremendous progress. However, the power conversion efficiency (PCE) of all‐PSCs still lags behind the polymer‐donor‐small‐molecule‐acceptor based organic solar cells, owing to the excessive phase separation with poor miscibility between polymer donor and acceptor. In this research, an “end‐capped” ternary strategy is proposed by introducing PM6TPO as a third component to fabricate highly efficient all‐PSCs. The PM6:PM6TPO:PY‐IT based ternary devices exhibit impressive PCE of 17.0% with enhanced light absorption and optimal morphology, and the introduction of PM6TPO significantly reduces the phase separation. The ternary devices also exhibit improved stability, outstanding tolerance of active layer thickness, and high performance of 1 cm2 unit cells. More importantly, the “end‐capped” ternary strategy enables efficient and facile improvement of all‐PSCs performance without additional selection and complicated synthesis for the third component.

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An end-capped strategy for crystalline polymer donor to improve the photovoltaic performance of non-fullerene solar cells

Cited by 10 publications

References 57 publications

Synthesis of Crown Ether End-Capped PM6 Copolymers with Tunable Molecular Weight for Organic Solar Cells

Synthesis of Crown Ether End-Capped PM6 Copolymers with Tunable Molecular Weight for Organic Solar Cells

A two-armed skeleton extension strategy for the design of novel spirobifluorene-based small molecule donors

All‐Polymer Solar Cells with 17% Efficiency Enabled by the “End‐Capped” Ternary Strategy

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