Over 17% efficiency ternary organic solar cells enabled by two non-fullerene acceptors working in an alloy-like model

Zhan, Lingling; Li, Shuixing; Lau, Tsz‐Ki; Cui, Yong; Lu, Xinhui; Shi, Minmin; Li, Chang‐Zhi; Li, Hanying; Hou, Jianhui; Chen, Hongzheng

doi:10.1039/c9ee03710a

Cited by 659 publications

(531 citation statements)

References 65 publications

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“…[ 1–6 ] Nonfullerene small molecular acceptors (SMAs) [ 7–29 ] are the main driving force for the recent development of the field, with power conversion efficiencies (PCEs) over 17% reported by different teams. [ 30–43 ] SMAs have many attractive properties including their strong and tunable absorption, the easily adjustable energy levels and the enhanced chemical and device stability. Most of these excellent features are enabled by the flexible and feasible synthesis of the SMAs that leads to numerous judiciously designed molecular structures.…”

Section: Methodsmentioning

confidence: 99%

Understanding the Effect of End Group Halogenation in Tuning Miscibility and Morphology of High‐Performance Small Molecular Acceptors

et al. 2020

Solar RRL

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A multitude of studies have been conducted on organic solar cells (OSCs) to understand how end group halogenation changes the property of the small molecular acceptors (SMAs) energetically, morphologically, and so on. But how the halogenation impacts the miscibility between SMAs and polymers, which is an important index to thermodynamically predict and understand the morphology of blend films, has not been systematically studied, particularly for the state‐of‐the‐art polymer–SMA blends. Herein, three series of asymmetric or symmetric SMAs, all reported recently with high photovoltaic performances, are used to investigate the effect of halogenation on miscibility, crystallinity, and solar cell performance. Using the asymmetric SMA named TPIC, and its derivatives (TPIC‐4F and TPIC‐4Cl) as the focus, it is revealed that the enhancement in solar cell performance for the halogenated SMAs is to reduce the miscibility between the acceptor and donor, which leads to a more favorable morphology, enhanced charge transport, and an extended absorption range. Similarly, the halogenation‐induced reduction in miscibility for the initially overmixed donor:acceptor blend is also demonstrated in the symmetric ITIC and the state‐of‐the‐art BTP series, where attractive power conversion efficiencies (PCEs) of 16.5% and 16.8%, respectively, are achieved by the halogenated‐SMA‐based devices in each series.

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Section: Methodsmentioning

confidence: 99%

Understanding the Effect of End Group Halogenation in Tuning Miscibility and Morphology of High‐Performance Small Molecular Acceptors

et al. 2020

Solar RRL

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“…During the past five years, polymer solar cells (PSCs) based on narrow bandgap (NBG) fused‐ring small molecule (SM) acceptors have made considerable progress, among which the state‐of‐the‐art PSCs have achieved power conversion efficiencies (PCEs) of 16–18% . Regarding such SM acceptor‐based PSCs, the all‐polymer solar cells (all‐PSCs) consisting of a polymer donor and a polymer acceptor show unique advantages in the flexible large‐scale and wearable energy generators due to their excellent morphology stability and mechanical robustness .…”

Section: Methodsmentioning

confidence: 99%

10.13% Efficiency All‐Polymer Solar Cells Enabled by Improving the Optical Absorption of Polymer Acceptors

Fan

Liu

et al. 2020

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During the past five years, polymer solar cells (PSCs) based on narrow bandgap (NBG) fused-ring small molecule (SM) acceptors have made considerable progress, [1][2][3][4] among which the state-of-the-art PSCs have achieved power conversion efficiencies (PCEs) of 16-18%. [5][6][7][8][9][10][11][12][13][14][15][16][17] Regarding such SM acceptor-based PSCs, the all-polymer solar cells (all-PSCs) consisting of a polymer donor and a polymer acceptor show unique advantages in the flexible large-scale and wearable energy generators due to their excellent morphology stability and mechanical robustness. [18][19][20][21] However, most of the efficient all-PSCs have PCEs ranging in 8-10%, [22][23][24][25][26][27][28][29][30][31][32][33][34] although a few of them achieved PCEs over 11%, [35][36][37] which is still far behind that of the efficient PSCs based on SM acceptors due to the lack of high-performance polymer acceptors. To date, polymer acceptors have been mainly confined into a small number of structural building blocks, [24][25][26][38][39][40] and the most widely studied one is the polymer N2200 with a donor-acceptor (D-A) backbone of naphthalene diimide (NDI)-alt-bithiophene due to its NBG and suitable molecular energy levels. [39][40][41][42][43] However, N2200 neat film suffers from a low absorption coefficient of %0.3 Â 10 5 cm À1 and an excess strong crystallinity and stacking, which usually lead to the limited photocurrent and large phase separation in active layers. [39][40][41][42][43] The limited light absorption capacity for most polymer acceptors hinders the improvement of the power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs). Herein, by simultaneously increasing the conjugation of the acceptor unit and enhancing the electron-donating ability of the donor unit, a novel narrowbandgap polymer acceptor PF3-DTCO based on an A-D-A-structured acceptor unit ITIC16 and a carbon-oxygen (C-O)-bridged donor unit DTCO is developed. The extended conjugation of the acceptor units from IDIC16 to ITIC16 results in a red-shifted absorption spectrum and improved absorption coefficient without significant reduction of the lowest unoccupied molecular orbital energy level. Moreover, in addition to further broadening the absorption spectrum by the enhanced intramolecular charge transfer effect, the introduction of C-O bridges into the donor unit improves the absorption coefficient and electron mobility, as well as optimizes the morphology and molecular order of active layers. As a result, the PF3-DTCO achieves a higher PCE of 10.13% with a higher short-circuit current density ( J sc ) of 15.75 mA cm À2 in all-PSCs compared with its original polymer acceptor PF2-DTC (PCE ¼ 8.95% and J sc ¼ 13.82 mA cm À2 ). Herein, a promising method is provided to construct high-performance polymer acceptors with excellent optical absorption for efficient all-PSCs.

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“…[ 6–12 ] BTP‐based NFAs originated by Zou's group, such as Y6 and its derivatives, possess unique features of dominant face‐on orientation, high mobility, and low energy loss with high electroluminescence quantum efficiency (EQE EL ) in devices, thus enabling OPVs with over 17% efficiencies. [ 13–19 ] It is interesting to note that efficient NFAs could exhibit relatively low energy loss and fast charge separation under small driving forces, compared with fullerene‐based acceptors. [ 20–22 ] Although some progresses have been made, energy loss in OPVs based on NFAs is still obviously large, compared to Si and perovskite counterparts.…”

Section: Figurementioning

confidence: 99%

Asymmetric Electron Acceptors for High‐Efficiency and Low‐Energy‐Loss Organic Photovoltaics

et al. 2020

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Low energy loss and efficient charge separation under small driving forces are the prerequisites for realizing high power conversion efficiency (PCE) in organic photovoltaics (OPVs). Here, a new molecular design of nonfullerene acceptors (NFAs) is proposed to address above two issues simultaneously by introducing asymmetric terminals. Two NFAs, BTP‐S1 and BTP‐S2, are constructed by introducing halogenated indandione (A1) and 3‐dicyanomethylene‐1‐indanone (A2) as two different conjugated terminals on the central fused core (D), wherein they share the same backbone as well‐known NFA Y6, but at different terminals. Such asymmetric NFAs with A1‐D‐A2 structure exhibit superior photovoltaic properties when blended with polymer donor PM6. Energy loss analysis reveals that asymmetric molecule BTP‐S2 with six chlorine atoms attached at the terminals enables the corresponding devices to give an outstanding electroluminescence quantum efficiency of 2.3 × 10−2%, one order of magnitude higher than devices based on symmetric Y6 (4.4 × 10−3%), thus significantly lowering the nonradiative loss and energy loss of the corresponding devices. Besides, asymmetric BTP‐S1 and BTP‐S2 with multiple halogen atoms at the terminals exhibit fast hole transfer to the donor PM6. As a result, OPVs based on the PM6:BTP‐S2 blend realize a PCE of 16.37%, higher than that (15.79%) of PM6:Y6‐based OPVs. A further optimization of the ternary blend (PM6:Y6:BTP‐S2) results in a best PCE of 17.43%, which is among the highest efficiencies for single‐junction OPVs. This work provides an effective approach to simultaneously lower the energy loss and promote the charge separation of OPVs by molecular design strategy.

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Over 17% efficiency ternary organic solar cells enabled by two non-fullerene acceptors working in an alloy-like model

Abstract: An alloy-like model based on Y6 and its derivative BTP-M is constructed to fabricate ternary organic solar cells, leading to a best efficiency of 17.03%.

Cited by 659 publications

References 65 publications

Understanding the Effect of End Group Halogenation in Tuning Miscibility and Morphology of High‐Performance Small Molecular Acceptors

Understanding the Effect of End Group Halogenation in Tuning Miscibility and Morphology of High‐Performance Small Molecular Acceptors

10.13% Efficiency All‐Polymer Solar Cells Enabled by Improving the Optical Absorption of Polymer Acceptors

Asymmetric Electron Acceptors for High‐Efficiency and Low‐Energy‐Loss Organic Photovoltaics

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