π–π stacking induced high current density and improved efficiency in ternary organic solar cells

Li, Lijuan; Lin, Hui; Kong, Xiao; Du, Xiaoyang; Chen, Xinwei; Zhou, Ling; Tao, Silu; Zheng, Caijun; Zhang, Shun

doi:10.1039/c8nr01421c

Cited by 12 publications

(14 citation statements)

References 57 publications

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“…In Figure 7, it is found that the WCA value is 99.44° of PTB7-Th:PC 70 BM, which is close to the pure film of PTB7-Th (103.28°), indicating that more PTB7-Th gather on the blend film superficially, in addition to the small amount of PC 70 BM molecules. [28,44] The miscibility between the different components is recognized as the key factor in determining the vertical and horizontal phase separation, and eventually the performance of solar cells. The WCA values are 102.04° of ternary films containing 10 wt% DRCN5T and 103.22° of ternary films containing 30 wt% DRCN5T, which are very close to the pure PTB7-Th film of 103.28°.…”

Section: Resultsmentioning

confidence: 99%

“…[42] There are multiple reasons for the poor performance of ternary OSCs with thicker active layer. [21,44] Weather the substrate character is hydrophobic or not, it is still unknown that what determines the morphological stability of thick active layer in the vertical direction. [38] Furthermore, as the blend film thickness increased, the effect of surface energy of substrates on the vertical distribution of donor and acceptor lessened, leading to the unfavorable enrichment of donors or acceptors at cathode and anode, which is harmful to the charge collection in the respective electrodes.…”

Section: Introductionmentioning

confidence: 99%

“…When the crystallization of donor or acceptor is disturbed by the incorporation of third additive, the decreased domain purity may lead to the depression of charge mobility and the enhanced charge recombination, causing the severe reduction of PCE and fill factor (FF) . Furthermore, as the blend film thickness increased, the effect of surface energy of substrates on the vertical distribution of donor and acceptor lessened, leading to the unfavorable enrichment of donors or acceptors at cathode and anode, which is harmful to the charge collection in the respective electrodes . Weather the substrate character is hydrophobic or not, it is still unknown that what determines the morphological stability of thick active layer in the vertical direction.…”

Section: Introductionmentioning

confidence: 99%

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Miscibility Tuning for Optimizing Phase Separation and Vertical Distribution toward Highly Efficient Organic Solar Cells

et al. 2019

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Blending multidonor or multiacceptor organic materials as ternary devices has been recognized as an efficient and potential method to improve the power conversion efficiency of bulk heterojunction devices or single‐junction components in tandem design. In this work, a highly crystalline molecule, DRCN5T, is involved into a PTB7‐Th:PC 70 BM system to fabricate large‐area organic solar cells (OSCs) whose blend film thickness is up to 270 nm, achieving an impressive performance of 11.1%. The significant improvement of OSCs after adding DRCN5T is due to the formation of an interconnected fibrous network with decreased π–π stacking and enhanced domain purity, in addition to the optimized vertical distribution of PTB7‐Th and PC 70 BM, producing more effective charge separation, transport, and collection. The optimized morphology and performance are actually determined by the miscibility in different components, which can be quantitatively described by the Flory–Huggins interaction parameter of −0.80 and 2.94 in DRCN5T:PTB7‐Th and DRCN5T:PC 70 BM blends, respectively. The findings in this work can potentially guide the selection of an appropriate third additive for high‐performance OSCs for the sake of large‐area printing and roll‐to‐roll fabrication from the view of miscibility.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Miscibility Tuning for Optimizing Phase Separation and Vertical Distribution toward Highly Efficient Organic Solar Cells

et al. 2019

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“…Table S3 (Supporting Information) shows the hole mobility properties that were calculated by using the space charge limited current method. The hole mobility was estimated by using the Mott–Gurney equation and by fabricating a hole only device (ITO/active layer/MoO 3 /Ag or ITO/PEDOT:PSS/active layer/MoO 3 /Ag)

J = (9 normal/ 8) μ ε_{0} ε_{normalr} (V^{2} normal/ L^{3})

where µ : Charge carrier mobility,ε 0 : Free‐space permittivity, ε r : Dielectric constant of the semiconductor, V : Applied voltage, L : Thickness of semiconductor layer. …”

Section: Resultsmentioning

confidence: 99%

Vertical Phase Separation for Highly Efficient Organic Solar Cells Incorporating Conjugated‐Polyelectrolytes

Han

Choi

Lee

et al. 2018

Adv Materials Inter

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OSCs can be applied to various fields due to their many advantages, such as high performance, low cost, flexibility, and potential for modulation. Recently, the research on OSCs has been focused on materials with high-performance organic donors and acceptors (fullerene and nonfullerene) and device structure research, such as ternary structure and tandem structure. These studies have contributed to developing high-performance OSCs with excellent power conversion efficiency (PCE) over 14% in single cells and 17.3% in tandem structure cells. [1][2][3][4][5][6][7][8][9][10] OSCs are based on an active layer that has a bulk-heterojunction (BHJ) structure that consists of an organic donor and acceptor, and OSCs generate excitons within the range of their optical properties. Additionally, OSCs show photovoltaic properties via the process of charge disassociation and charge transport. [11,12] Due to the limitation of the optical properties of organic donors and acceptors, carrier mobility and carrier balance are critical factors that determine the performance of OSCs. [13][14][15][16] Therefore, photogenerated carriers that have been generated in a BHJ have the disadvantage of exhibiting a lower mobility compared with inorganic semiconductor-based solar cells because of the organic semiconductor's inherent properties, such as monomolecular recombination and bimolecular recombination. [17][18][19] Additionally, certain of these photogenerated carriers return to the ground state through monomolecular trap-assisted recombination, [20][21][22] interfacial recombination, [23][24][25] and surface trap-assisted recombination, [26] and the carriers subsequently weaken the device performance because the reduction of current and internal potential occurs via a nonradiative relaxation process. [27,28] Therefore, it is necessary to enhance the carrier transport properties to improve the performance of OSCs.Recent research has reported important device structure modifications to improve the carrier transport properties of OSCs. Specifically, the carrier mobility can be increased by introducing a buffer layer through enhancing carrier transport, and the device performance can be enhanced by reducing the recombination. Hybrid organic solar cells are made through a simple one-pot coating process with conjugated polyelectrolytes (CPEs), poly[9,9-bis(4′sulfonatobutyl)fluorenealt-thiophene-doped (PFT-D). The hybrid active layer incorporated with PFT-D shows vertical phase separation by selfassembled properties of PFT-D, which result from a molecular dipole between the conjugated backbone and the side chain. The hybrid activelayer with PFT-D shows that homogeneous morphology, surface potential properties, and hydrophobic surface properties favor for enhancing photovoltaic performance. These results are identified by contact angle characteristics, X-ray photoelectron spectroscopy (XPS) profiling, and X-ray diffraction (XRD), atomic force measurement (AFM), and electrostatic force measurement (EFM) analyses. With fullerene based hybrid active...

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“…The photovoltaic performance of BHJ PSCs was highly dependent on the semiconductor materials used as the photoactive layer. Thus, tremendous efforts in the past decades have been devoted to exploring excellent semiconducting materials, such as conjugated copolymers (CPs) and small molecules (SMs), and the use of various additives to modulate the morphology and optimization of processing techniques [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. Recently, with the help of novel materials, improved morphology, much more profound understanding of the structure-performance correlation and the photon-to-electron conversion mechanism, and power conversion efficiencies (PCEs) for PSCs in the single-junction module of over 11% in fullerene systems [35] and over 16% in non-fullerene systems [36][37][38][39] were achieved.…”

Section: Introductionmentioning

confidence: 99%

Fluorination Effect for Highly Conjugated Alternating Copolymers Involving Thienylenevinylene-Thiophene-Flanked Benzodithiophene and Benzothiadiazole Subunits in Photovoltaic Application

Huang

Wang

et al. 2020

Polymers

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Two two-dimensional (2D) donor–acceptor (D-A) type conjugated polymers (CPs), namely, PBDT-TVT-BT and PBDT-TVT-FBT, in which two ((E)-(4,5-didecylthien-2-yl)vinyl)- 5-thien-2-yl (TVT) side chains were introduced into 4,8-position of benzo[1,2-b:4,5-bʹ]dithiophene (BDT) to synthesize the highly conjugated electron-donating building block BDT-TVT, and benzothiadiazole (BT) and/or 5,6-difluoro-BT as electron-accepting unit, were designed to systematically ascertain the impact of fluorination on thermal stability, optoelectronic property, and photovoltaic performance. Both resultant copolymers exhibited the lower bandgap (1.60 ~ 1.69 eV) and deeper highest occupied molecular orbital energy level (EHOMO, –5.17 ~ –5.37 eV). It was found that the narrowed absorption, deepened EHOMO and weakened aggregation in solid film but had insignificant influence on thermal stability after fluorination in PBDT-TVT-FBT. Accordingly, a PBDT-TVT-FBT-based device yielded 16% increased power conversion efficiency (PCE) from 4.50% to 5.22%, benefited from synergistically elevated VOC, JSC, and FF, which was mainly originated from deepened EHOMO, increased μh, μe, and more balanced μh/μe ratio, higher exciton dissociation probability and improved microstructural morphology of the photoactive layer as a result of incorporating fluorine into the polymer backbone.

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π–π stacking induced high current density and improved efficiency in ternary organic solar cells

Cited by 12 publications

References 57 publications

Miscibility Tuning for Optimizing Phase Separation and Vertical Distribution toward Highly Efficient Organic Solar Cells

Miscibility Tuning for Optimizing Phase Separation and Vertical Distribution toward Highly Efficient Organic Solar Cells

Vertical Phase Separation for Highly Efficient Organic Solar Cells Incorporating Conjugated‐Polyelectrolytes

Fluorination Effect for Highly Conjugated Alternating Copolymers Involving Thienylenevinylene-Thiophene-Flanked Benzodithiophene and Benzothiadiazole Subunits in Photovoltaic Application

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