Enhanced device performance of organic solar cells via reduction of the crystallinity in the donor polymer

Park, Jong Hwan; Park, Jeong‐Il; Kim, Do Hwan; Kim, Joohyun; Kim, Jong Soo; Lee, Ji Hwang; Sim, Myungsun; Lee, Sang Yoon; Cho, Kilwon

doi:10.1039/c0jm00664e

Cited by 26 publications

(16 citation statements)

References 37 publications

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“…As evidenced by transmission electron microscopy (TEM) images (Figure h vs 5i) and blend electron mobility ( µ e ) (Table S1, Supporting Information, PTBB‐ p blend: 2.54 × 10 −4 cm 2 V −1 s −1 vs PTBB‐ m blend: 2.15 × 10 −4 cm 2 V −1 s −1 ) results. The increased acceptor aggregation in PTBB‐ p blend films may cause more exciton recombination and lower hole mobility than in PTBB‐ m blend films . This is also evidenced by the following light‐intensity experiments, the exciton recombination increases from PTBB‐ m blend ( S = 0.988) to PTBB‐ p blend ( S = 0.978) (Figure d).…”

Section: Resultssupporting

confidence: 65%

Steric Engineering of Alkylthiolation Side Chains to Finely Tune Miscibility in Nonfullerene Polymer Solar Cells

Xue

Weng

Feng

et al. 2018

Advanced Energy Materials

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advantages of simple device structure, light weight, and low fabrication cost by solution-processing. [1][2][3][4][5][6][7][8][9][10][11] Despite the great achievement in fullerene PSCs, fullerene acceptors still suffer from several drawbacks, including high-cost purification, poor morphological stability, and weak absorption in visible wavelength range. To solve these problems, considerable research efforts have been dedicated to nonfullerene acceptors, especially smallmolecular acceptors (SMAs). [12][13][14][15][16][17][18][19][20] Recently, emerging SMAs have been demonstrated as alternatives to fullerene acceptors because the excellent photovoltaic performance with power conversion efficiency (PCE) has reached 12-14% recently. [18][19][20][21] To achieve more efficient SMA PSCs, it is essential to design donor polymers that can match with SMAs through favorable morphology as the device performance of PSCs is strongly dependent on the blend morphology. Therefore, morphology controlling has become one of research key points and still faces a great challenge. Some practical physical strategies have been developed such as ternary blend, additives, thermal annealing, etc., to finely tune blend morphology and form miscible donor/acceptor mixture. [22,23] In the meantime, exploitation of chemical tools as an alternative strategy to control blend morphology is showing its advantages in finely molecular-scaled controlling. [24] One of the most commonly used chemical strategies for tuning morphology is through the fluorination or alkylthiolation of the polymeric side chains to tune the solubility, aggregation properties, and thus the good miscibility with acceptors. [25] In comparison with the high cost and complex synthetic route of fluorinated modification on polymer side chains, low cost of alkylthiolation is obviously synthetic superior to the former. However, in recent literatures it is found that, on the one hand, the alkylthiolation of polymer side chains can improve polymeric crystallinity and mobility and lead to a high photovoltaic performance; [26,27] on the other hand, the strengthened crystallinity after the alkylthiolation for high crystalline polymer may form dense and isolated polymer domains, which causes serious phase separation and destroys the miscibility at donor/acceptor interfaces. [24,28,29] As the thermodynamic miscibility between donor and acceptor mainly drives the phase separation degree, therefore, Morphology and miscibility control are still a great challenge in polymer solar cells. Despite physical tools being applied, chemical strategies are still limited and complex. To finely tune blend miscibility to obtain optimized morphology, chemical steric engineering is proposed to systemically investigate its effects on optical and electronic properties, especially on a balance between crystallinity and miscibility. By changing the alkylthiol side chain orientation different steric effects are realized in three different polymers. Surprisingly, the photovoltaic device of the polymer PTBB-m with...

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Section: Resultssupporting

confidence: 65%

Steric Engineering of Alkylthiolation Side Chains to Finely Tune Miscibility in Nonfullerene Polymer Solar Cells

Xue

Weng

Feng

et al. 2018

Advanced Energy Materials

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“…Generally, formation of long‐ranged interpenetrating networks will help the carrier transport. Otherwise, the domain‐to‐domain electronic connectivity has impacts on the carrier mobility . In our cases, the higher carrier mobility for 4T‐BDT is supposedly originated from stronger electronic connectivity between the crystalline aggregate domains.…”

Section: Discussionmentioning

confidence: 62%

Boosting Organic Solar Cell Electrical Performance by Introducing Large Aromatics onto Small‐Molecule Peripheral Side‐Chains

Zhang

Yao

Chen

2016

Adv Materials Inter

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It is reported herein that electrical performance of diketopyrrolopyrrole based small‐molecule solar cells are boosted via increasing the conjugation size fraction (δ) on lateral side‐chains and on the mainchain of small‐molecule donor. The conjugation size fraction is defined as δ = N p/N m, where N p is the number of five‐ or six‐member aromatic rings on the peripheral side‐chains and N m is that on the mainchain. As the DPP‐dimer's core structure varies from 5,10‐bis((5‐(2‐ethylhexyl)thiophen‐2‐yl)dithieno[2,3‐d:2′,3′‐d′]benzo[1,2‐b:4,5‐b′]dithiophene (DT‐BDT) to 4,8‐bis((5‐(2‐ethylhexyl)thiophen‐2‐yl)‐BDT (2T‐BDT), and then 4,8‐bis(5′‐(2‐ethylhexyl)‐(2,2′‐bithiophen)‐5‐yl)‐BDT (4T‐BDT), the term of δ increases from 2/13 to 2/11 and then 4/11. In the blended film with the fullerene acceptor, the donor phase size decreases from 35 to 24 and 15 nm, becoming more and more approaching to the effective exciton diffusion length. Consequently, the obtainable maximum generation rate of electron–hole bound pairs increases from 7.0 × 1027 to 7.3 × 1027 and then 7.7 × 1027 m−3 s−1. Meanwhile, reduction of donor crystallinity with the increase of δ leads to a higher effective carrier mobility, which suppresses recombination losses and leads to a larger carrier collection probability. Promotions of both charge separation and transport give a larger short‐circuit current density, a higher fill‐factor, and ultimately a larger efficiency.

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“…A slight decrease in the diffraction peak intensity is also observed with the addition of GQDs‐green, which may be one of the reasons why the GQDs can enhance the photovoltaic performance of the blend films. Actually, the reduction in the crystallinity can enhance the photovoltaic performance of the polymeric solar cells as reported by others …”

Section: Resultsmentioning

confidence: 72%

Graphene Quantum Dots Band Structure Tuned by Size for Efficient Organic Solar Cells

Zhang

Shen

et al. 2019

Physica Status Solidi (a)

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The electronic states of graphene quantum dots (GQDs) can be tuned by varying the lateral size and edge structure, which further influence their optoelectronic properties and the applications. Herein, three kinds of GQDs with different lateral size are prepared by photon-Fenton reaction and separated through gel column chromatography, and their effects on the photovoltaic performances of inverted organic solar cells based on the poly(3-hexylthiophene) (P3HT) and poly(3-hexylthiophene)/(6,6)-phenyl-C61 butyric acid methylester (PCBM) blend films are studied systematically. In comparison with P3HT:PCBM cells, the power conversion efficiency of the P3HT:PCBM solar cells containing 0.8% of GQDs-blue, GQDs-green, and GQDs-orange can be increased from 3.06% to 3.54%, 4.43%, and 3.73% with a short-circuit current density of 10.3, 13.34, and 11.19 mA cm À2 . It is illustrated also that the band structures (electronic energy states) tuned mainly by their lateral size of GQDs are the crucial factor to dominate their photovoltaic preferences as additives in conventional P3HT:PCBM solar cells.

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Enhanced device performance of organic solar cells via reduction of the crystallinity in the donor polymer

Cited by 26 publications

References 37 publications

Steric Engineering of Alkylthiolation Side Chains to Finely Tune Miscibility in Nonfullerene Polymer Solar Cells

Steric Engineering of Alkylthiolation Side Chains to Finely Tune Miscibility in Nonfullerene Polymer Solar Cells

Boosting Organic Solar Cell Electrical Performance by Introducing Large Aromatics onto Small‐Molecule Peripheral Side‐Chains

Graphene Quantum Dots Band Structure Tuned by Size for Efficient Organic Solar Cells

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