Highly crystalline low-bandgap polymer nanowires towards high-performance thick-film organic solar cells exceeding 10% power conversion efficiency

Lee, Jawon; Sin, Dong Hun; Moon, Byungho; Shin, Jisoo; Kim, Heung Gyu; Kim, Min; Cho, Kilwon

doi:10.1039/c6ee02466a

Cited by 136 publications

(119 citation statements)

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“…[1] However, the majority of PV cell types, such as Si, [2] CuIn x Ga 1−x Se y S 1−y (CIGS), [3] Cu 2 ZnSnS 4−x Se x (CZTS), [4] GaAs, [5] CdTe, [6] dye-sensitized (DSSC), [7] perovskite, [8] and organic solar cells, [9] still suffer from low external quantum efficiency (EQE) in the UV wavelength region due to surface and direct bandgap with facile and wide tunability. [1] However, the majority of PV cell types, such as Si, [2] CuIn x Ga 1−x Se y S 1−y (CIGS), [3] Cu 2 ZnSnS 4−x Se x (CZTS), [4] GaAs, [5] CdTe, [6] dye-sensitized (DSSC), [7] perovskite, [8] and organic solar cells, [9] still suffer from low external quantum efficiency (EQE) in the UV wavelength region due to surface and direct bandgap with facile and wide tunability.…”

Section: Introductionmentioning

confidence: 99%

One‐Pot Gram‐Scale, Eco‐Friendly, and Cost‐Effective Synthesis of CuGaS₂/ZnS Nanocrystals as Efficient UV‐Harvesting Down‐Converter for Photovoltaics

Jalalah

Al-Assiri

Park

2018

Advanced Energy Materials

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reflection, scattering, and thermalization losses, which limit conversion efficiency. [10] These losses are mostly caused by the energy difference between the incident UV photons (>3.2 eV) and bandgap of PV cells (1.0-1.6 eV). [11] If these photons are not surface reflected, their excess energy will be adversely dissipated in cells as heat via the nonradiative relaxation of the photoexcited electronhole pairs leading to further limitations and faster degradation of PV cells. [12] One of the most promising approaches to overcome these limitations is to implement the surfaces of PV devices with an energydownshift quantum-dot (EDS-QD) layer to harvest the wasted UV photons and reemit them at visible wavelengths absorbed more efficiently by PV cells. [13] Moreover, EDS-QDs have been well demonstrated as an effective layer that boosts the energy density, then the usage active area of PV cells could be reduced by the same percentage of enhancement in PV efficiency for a defined amount of power. Due to the enhanced efficiency along with the low cost of preparing EDS-QDs, the cost of PV electricity generation could be effectively minimized. [1d,14] For the abovementioned reasons, the concept of the EDS-QD layer was proposed for solar energy conversion for both increasing the efficiency and lessening the cost.Motivated by these purposes and attracted by their excellent optical properties, Cd-based core/shell QDs, such as CdSe/ CdS, [13c,15] CdSe/CdZnS, [16] CdSe/ZnS, [11b] and Cd 0.5 Zn 0.5 S/ ZnS [13b,17] QDs have been used recently as EDS layers. However, the relying on the Cd-based QDs in commercial solar cells has been limited due to two main reasons; the toxicity of Cd metal ions [18] and the self-reabsorption losses within their QDs. [13a] For the latter, Mn-doped Cd 0.5 Zn 0.5 S/ZnS QDs have been introduced more recently [13a,14a] as an excellent EDS-QD layer having free-self-reabsorption with large Stokes shift, yet with environmentally hazardous Cd material. [19] As a result, the quest for nontoxic high photoluminescence-quantum yield (PLQY) and the zero-self-reabsorption EDS-QD layer is a priority for their commercial applications.Alternatively, chalcogenide CIGS is one of the most promising semiconductor materials for EDS-QD layers due to its beneficial properties of large absorption coefficient (10 5 cm −1 ), [20] eco-friendly nature, [19,21] long-term stability, [22] It is presented for the first time nontoxic CuGaS 2 /ZnS quantum dots (QDs) with free-self-reabsorption losses and large Stokes shift (>190 nm) synthesized on an industrially gram-scale as an alternative for Cd-based energydownshift (EDS)-QD layers. The QDs exhibit a typical EDS that absorbs only UV light (<407 nm) and emits the whole range of visible light (400-800 nm) with a high photoluminescence-quantum yield of ≈76%. The straightforward application of these EDS-QDs on the front surface of a monocrystalline p-type silicon solar cell significantly enhances the short-circuit current density by ≈1.64 mA cm −2 (+4.20%); thereby, improving ...

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Section: Introductionmentioning

confidence: 99%

One‐Pot Gram‐Scale, Eco‐Friendly, and Cost‐Effective Synthesis of CuGaS₂/ZnS Nanocrystals as Efficient UV‐Harvesting Down‐Converter for Photovoltaics

Jalalah

Al-Assiri

Park

2018

Advanced Energy Materials

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“…Bulk heterojunction (BHJ) OSCs are being extensively researched as a clean energy source with efficiencies exceeding 10% 1–5 . In most of the high-efficiency BHJ-OSCs, the fullerene derivative PC 70 BM is a common constituent, which is used as an electron accepting material in the photoactive layer.…”

Section: Introductionmentioning

confidence: 99%

Unraveling the efficiency-limiting morphological issues of the perylene diimide-based non-fullerene organic solar cells

Singh

Suranagi

Lee

et al. 2018

Sci Rep

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Herein we report a comparative morphological analysis of the perylene diimide (PDI)- and fullerene-based organic solar cells (OSCs) to identify the factors responsible for low performance of PDI-based devices. A PDI derivative, bis-PDI, and a fullerene derivative, PC70BM, are mixed with an efficient polymer donor, PffBT4T-2OD. The large disparity in power conversion efficiencies (PCEs) of OSCs composed of PffBT4T-2OD:bis-PDI (PCE = 5.18%) and PffBT4T-2OD:PC70BM (PCE = 10.19%) observed are attributed to differences in the nanostructural motif of bulk heterojunction (BHJ) morphologies of these blend systems. The X-ray scattering and surface energy characterizations revealed that the structurally dissimilar bis-PDI and PC70BM molecules determine the variation in blend film morphologies, and in particular, the molecular packing features of the donor PffBT4T-2OD polymer. In addition, high-resolution transmission electron microscopy (HRTEM) images explore the BHJ morphologies and presence of longer polymer fibrils in PffBT4T-2OD:bis-PDI system, justifying the unbalanced charge transport and high hole mobility. The low performance of PffBT4T-2OD:bis-PDI devices was further investigated by studying charge carrier recombination dynamics by using light-intensity-dependent and transient photovoltage (TPV) experiments. Furthermore, the temperature-dependent experiments showed the photovoltaic properties, including charge recombination losses, are strongly affected by energetic disorder present in bis-PDI-based system.

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“…The intense (100) diffraction peak (q z = 0.41 Å −1 ) of the as-spun COTIC-4F is dominantly observed, indicating that the texture adopts edge-on crystallites with respect to the substrate. [42] In both NFA blends, the inter-lamellae (100) region in the in-plane direction and π-π stacking (010) region in the out-of-plane direction contain features from the PTB7-Th and NFA components that cannot be easily separated. The (010) diffractions of NFA neat films along the out-of-plan direction correspond to a π-π stacking distance of ≈3.4 Å, which is smaller than that of the as-spun PTB7-Th (≈3.8 Å).…”

mentioning

confidence: 98%

Bandgap Narrowing in Non‐Fullerene Acceptors: Single Atom Substitution Leads to High Optoelectronic Response Beyond 1000 nm

Lee

Seifrid

et al. 2018

Advanced Energy Materials

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144

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absorption spectra extending to the NIR region have been designed and applied to the fabrication of OSCs. [6][7][8] A critical challenge arises as one decreases optical bandgaps (E g opt ) with respect to simultaneously achieving a high external quantum efficiency (EQE) and high open-circuit voltage (V OC ). [9] This challenge is due to the counterbalance between the driving force for charge separation, which aids in photocurrent generation, and voltage loss in the cell. [10,11] Finding ways to maximize V OC requires one to reduce the energy loss (E loss = E g opt -eV OC ) that occurs as a result of the multiple states that follow exciton generation. [12] Narrow bandgap (NBG) non-fullerene acceptors (NFAs) have emerged as the next generation of electron acceptors in OSCs. [13][14][15][16][17][18] Tunability of E g opt through molecular design allows one to tailor NIR absorption characteristics. [19,20] Considering that the maximum human photopic sensitivity is 555 nm and the maximum human scotopic sensitivity is 507 nm, [21] transparent photoactive materials should predominantly absorb solar radiation from ≈650 nm into the NIR region for semitransparent solar cell applications. In addition, since ≈50% of solar radiation intensity is in the NIR region, the development of NBG-NFAs with E g opt below ≈1.35 eV is desirable to effectively harvest solar NIR radiation. [1] Another encouraging feature of NFAs is that the energetic offsets that drive charge generation are small (<0.3 eV), [18,[22][23][24] which is beneficial for maintaining low E loss . Despite these desirable features, there has been less consideration for designing NBG-NFAs for transparent/NIR absorbing OSC applications. To address this challenge and expand the design of NIR harvesting acceptor molecules, we demonstrate in this contribution a new molecular design for ultra NBG-NFA materials with strong NIR response and small E loss .The two NBG NFAs described in this contribution are COTIC-4F and SiOTIC-4F (Figure 1a). Their molecular design includes incorporation of a cyclopentadithiophene (CPDT), or dithienosilole (DTS), unit as the central donor (D) fragment, which is flanked by two alkoxythienyl units (D′) to form an electron-rich D′-D-D′ central core. The D′-D-D′ units are end-capped with Two narrow bandgap non-fullerene acceptors (NBG-NFAs), namely, COTIC-4F and SiOTIC-4F, are designed and synthesized for the fabrication of efficient near-infrared organic solar cells (OSCs). The chemical structures of the NBG-NFAs contain a D′-D-D′ electron-rich internal core based on a cyclopentadithiophene (or dithienosilole) (D) and alkoxythienyl (D′) core, end-capped with the highly electron-deficient unit 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (A), ultimately providing a A-D′-D-D′-A molecularconfiguration that enhances the intramolecular charge transfer characteristics of the excited states. One can thereby reduce the optical bandgap (E g opt ) to as low as ≈1.10 eV, one of the smallest values for NFAs reported to date. In bulk-he...

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Highly crystalline low-bandgap polymer nanowires towards high-performance thick-film organic solar cells exceeding 10% power conversion efficiency

Abstract: One-dimensional low bandgap polymer nanowires successfully incorporated into bulk-heterojunction organic solar cells, yielding a high PCE exceeding 10% with thick films.

Cited by 136 publications

References 51 publications

One‐Pot Gram‐Scale, Eco‐Friendly, and Cost‐Effective Synthesis of CuGaS₂/ZnS Nanocrystals as Efficient UV‐Harvesting Down‐Converter for Photovoltaics

One‐Pot Gram‐Scale, Eco‐Friendly, and Cost‐Effective Synthesis of CuGaS₂/ZnS Nanocrystals as Efficient UV‐Harvesting Down‐Converter for Photovoltaics

Unraveling the efficiency-limiting morphological issues of the perylene diimide-based non-fullerene organic solar cells

Bandgap Narrowing in Non‐Fullerene Acceptors: Single Atom Substitution Leads to High Optoelectronic Response Beyond 1000 nm

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Highly crystalline low-bandgap polymer nanowires towards high-performance thick-film organic solar cells exceeding 10% power conversion efficiency

Abstract: One-dimensional low bandgap polymer nanowires successfully incorporated into bulk-heterojunction organic solar cells, yielding a high PCE exceeding 10% with thick films.

Cited by 136 publications

References 51 publications

One‐Pot Gram‐Scale, Eco‐Friendly, and Cost‐Effective Synthesis of CuGaS2/ZnS Nanocrystals as Efficient UV‐Harvesting Down‐Converter for Photovoltaics

One‐Pot Gram‐Scale, Eco‐Friendly, and Cost‐Effective Synthesis of CuGaS2/ZnS Nanocrystals as Efficient UV‐Harvesting Down‐Converter for Photovoltaics

Unraveling the efficiency-limiting morphological issues of the perylene diimide-based non-fullerene organic solar cells

Bandgap Narrowing in Non‐Fullerene Acceptors: Single Atom Substitution Leads to High Optoelectronic Response Beyond 1000 nm

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One‐Pot Gram‐Scale, Eco‐Friendly, and Cost‐Effective Synthesis of CuGaS₂/ZnS Nanocrystals as Efficient UV‐Harvesting Down‐Converter for Photovoltaics

One‐Pot Gram‐Scale, Eco‐Friendly, and Cost‐Effective Synthesis of CuGaS₂/ZnS Nanocrystals as Efficient UV‐Harvesting Down‐Converter for Photovoltaics