Alkyl Chain Tuning of Small Molecule Acceptors for Efficient Organic Solar Cells

Jiang, Kui; Wei, Qiuping; Lai, Joshua Yuk Lin; Peng, Zhengxing; Kim, Ha Kyung; Yuan, Jun; Ye, Long; Zou, Yingping; Yan, He

doi:10.1016/j.joule.2019.09.010

Cited by 804 publications

(666 citation statements)

References 50 publications

(59 reference statements)

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“…Therefore, an extremely small E loss of 0.521 eV was obtained, which is the best record for PSCs with PCEs over 16% at present ( Figure 3d; Table S3, Supporting Information). [7][8][9][10][11][12][13][52][53][54][55] Our results showed these Adv. Funct.…”

Section: Photovoltaic Propertiessupporting

confidence: 60%

Subtle Polymer Donor and Molecular Acceptor Design Enable Efficient Polymer Solar Cells with a Very Small Energy Loss

Feng

Lee

et al. 2020

Adv Funct Materials

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A new wide bandgap polymer donor, PNDT‐ST, based on naphtho[2,3‐b:6,7‐b′]dithiophene (NDT) and 1,3‐bis(thiophen‐2‐yl)‐5,7‐bis(2‐ ethylhexyl)benzo[1,2‐c:4,5‐c′]dithiophene‐4,8‐dione (BDD) is developed for efficient nonfullerene polymer solar cells. To better match the energy levels, a new near infrared small molecule of Y6‐T is also developed. The extended π‐conjugation and less twist of PNDT‐ST provides it with higher crystallinity and stronger aggregation than the PBDT‐ST counterpart. The higher lowest occupied molecular orbital level of Y6‐T than Y6 favors the better energy level match with these polymers, resulting in improved open circuit voltage (Voc) and power conversion efficiency (PCE). The high crystallinity and strong aggregation of PNDT‐ST also induces large phase separation with poorer morphology, leading to lower fill factor and reduced PCE than PBDT‐ST. To mediate the crystallinity and optimize the morphology, PNDT‐ST and PBDT‐ST are blended together with Y6‐T, forming the ternary blend devices. As expected, the two compatible polymers allow continual optimization of the morphology by varying the blend ratio. The optimized ternary blend devices deliver a champion PCE as high as 16.57% with a very small energy loss (Eloss) of 0.521 eV. Such small Eloss is the best record for polymer solar cells with PCEs over 16% to date.

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Section: Photovoltaic Propertiessupporting

confidence: 60%

Subtle Polymer Donor and Molecular Acceptor Design Enable Efficient Polymer Solar Cells with a Very Small Energy Loss

Feng

Lee

et al. 2020

Adv Funct Materials

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“…It should be noted that over 11% PCE with nearly 70% FF for active layer thickness of 445 nm and over 10% PCE with FF of nearly 64% for active layer thickness of 510 nm are the best values among reported results of thick‐film OSCs to date (Table S1, Supporting Information). Nowadays, Y6 has garnered great attentions in the field of organic photovoltaics due to over 16% PCEs achieved in Y6‐based OSCs . PM6:Y6‐based single‐junction devices performed best at film thickness of 150 nm with a V oc of 0.83 V, a J sc of 25.3 mA cm −2 , an FF of 74.8%, and a high PCE of 15.7% .…”

Section: Resultsmentioning

confidence: 99%

“…Their easily‐tailored chemical structures allow judicious optimization of optical properties, energy levels and crystallization/aggregation properties . The power conversion efficiencies (PCEs) of OSCs have grown rapidly in the past two decades: from an initial PCE of 1% to more than 16% nowadays in single‐junction devices . Though continuous progression on developing SMAs has enabled high‐performance OSCs, there are still several critical issues need to be overcome for the purpose of practical applications .…”

Section: Introductionmentioning

confidence: 99%

Thick‐Film Organic Solar Cells Achieving over 11% Efficiency and Nearly 70% Fill Factor at Thickness over 400 nm

Gao

Hao

et al. 2020

Adv Funct Materials

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Thickness‐insensitive small molecule acceptors (SMAs) are still a great challenge for developing thick‐film organic solar cells (OSCs) towards practical use. Herein, two SMAs, MF1 and MF2, are designed and synthesized by employing a bifunctional end group with fluorine and methyl moieties. Combined with fused‐ring cores with alkyl side chains, both MF1 and MF2 exhibit ordered π–π stacking and high charge carrier mobilities in neat and blend films. The champion devices based on PM7:MF1 and PM7:MF2 deliver high power conversion efficiencies (PCEs) of 12.4% and 13.7%, and high fill factors (FFs) of 78.3% and 74.5%, respectively. With increasing active layer thickness, the FFs of the OSCs decrease relatively slowly, demonstrating the preferrable properties of MF1 and MF2 in terms of their thickness insensitivity, especially for MF1. As a result, the two thick‐film OSCs achieve over 11% PCEs at an active layer thickness over 400 nm (an FF close to 70% for PM7:MF1) and over 10% PCEs when the thickness is increased up to 500 nm. These are the highest PCEs among OSCs with such active layer thicknesses to date. This work reveals a molecular design strategy by reasonably combining fluorine and methyl together to simultaneously enhance charge carrier mobilities and fine‐tune the morphology, which is beneficial to achieve high‐performance thick‐film OSCs.

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“…Recently, rapid progress in bulk heterojunction organic solar cells (OSCs) have been achieved due to the advances in new materials and device engineering. [ 1–7 ] It is well known that the sufficient photon harvesting is prerequisite to obtain efficient OSCs. [ 8,9 ] In fact, organic semiconducting materials have a relatively narrow photon harvesting range with full width at half maximum about 100 nm, leading to the limited photon harvesting of active layers containing one donor material and one acceptor material.…”

Section: Introductionmentioning

confidence: 99%

Over 15.7% Efficiency of Ternary Organic Solar Cells by Employing Two Compatible Acceptors with Similar LUMO Levels

Yang

Gao

et al. 2020

Small

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Efficient organic solar cells (OSCs) are fabricated using polymer PM6 as donor, and IPTBO‐4Cl and MF1 as acceptors. The power conversion efficiency (PCE) of IPTBO‐4Cl based and MF1 based binary OSCs individually arrive to 14.94% and 12.07%, exhibiting markedly different short circuit current density (JSC) of 23.18 mA cm−2 versus 17.01 mA cm−2, fill factor (FF) of 72.17% versus 78.18% and similar open circuit voltage (VOC) of 0.893 V versus 0.908 V. The two acceptors, IPTBO‐4Cl and MF1, have similar lowest unoccupied molecular orbital levels, which is beneficial for efficient electron transport in the ternary active layer. The PCE of optimized ternary OSCs arrives to 15.74% by incorporating 30 wt% MF1 in acceptors, resulting from the simultaneously increased JSC of 23.20 mA cm−2, VOC of 0.897 V, and FF of 75.64% in comparison with IPTBO‐4Cl based binary OSCs. The gradually increased FFs of ternary OSCs indicate the well‐optimized phase separation and molecular arrangement with MF1 as morphology regulator. This work may provide a new viewpoint for selecting an appropriate third component to achieve efficient ternary OSCs from materials and photovoltaic parameters of two binary OSCs.

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Alkyl Chain Tuning of Small Molecule Acceptors for Efficient Organic Solar Cells

Cited by 804 publications

References 50 publications

Subtle Polymer Donor and Molecular Acceptor Design Enable Efficient Polymer Solar Cells with a Very Small Energy Loss

Subtle Polymer Donor and Molecular Acceptor Design Enable Efficient Polymer Solar Cells with a Very Small Energy Loss

Thick‐Film Organic Solar Cells Achieving over 11% Efficiency and Nearly 70% Fill Factor at Thickness over 400 nm

Over 15.7% Efficiency of Ternary Organic Solar Cells by Employing Two Compatible Acceptors with Similar LUMO Levels

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