High Efficiency Polymer Solar Cells with Efficient Hole Transfer at Zero Highest Occupied Molecular Orbital Offset between Methylated Polymer Donor and Brominated Acceptor

Sun, Chenkai; Qin, Shucheng; Wang, Rui; Chen, Shanshan; Pan, Fei; Qiu, Beibei; Shang, Ziya; Meng, Lei; Zhang, Chunfeng; Xiao, Min; Yang, Changduk; Li, Yongfang

doi:10.1021/jacs.9b09939

Cited by 354 publications

(298 citation statements)

References 52 publications

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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

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, [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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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

Solar RRL

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“…It is well‐known that fast charge separation under small driving force (<0.3 eV) can be realized for NFA systems. [ 22,43–45 ] The driving force can also be simplified as the energy level offsets between the donors and acceptors. Although the above phenomenon is common, there still remain many puzzles to be solved.…”

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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“…These end groups were synthesized based on a recently developed mono‐bromobenzene‐fused end group (named IC‐Br). [ 47,54,55 ] By introducing a Cl atom to the other sites on the benzene ring, the three position isomeric end groups, namely, IC‐ClBr, IC‐ClBr1, and IC‐ClBr2 ( Figure 1 ), were synthesized. When linked to the BTP core, the three end groups provided us with three isomeric SMAs, namely BTP‐ClBr, BTP‐ClBr1, and BTP‐ClBr2.…”

Section: Figurementioning

confidence: 99%

Altering the Positions of Chlorine and Bromine Substitution on the End Group Enables High‐Performance Acceptor and Efficient Organic Solar Cells

Luo

Chen

et al. 2020

Advanced Energy Materials

103

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Molecular design of organic semiconductors plays an important role in development of organic solar cell (OSC) materials and devices. [1-6] It is generally believed that subtle structural changes could lead to significant variations in the optoelectronic properties and photovoltaic performance of organic semiconductors. In particular, many of such examples have been demonstrated in the area of nonfullerene small-molecule acceptors (SMAs), [7-16] which has been a major revolution of the OSC field in the past few years. Thanks to their easily modified chemical structures, the electrochemical, optoelectronic, and physical properties of the molecules can be tuned and optimized to achieve efficient donor and acceptor materials. [17-26] To date, the OSCs based on nonfullerene SMAs and polymer donors have demonstrated efficiencies of over 17%. [27-39] It is widely recognized that subtle changes in the chemical structure of organic semiconductors can induce dramatic variations in their optoelectronic properties and device performance, especially for the nonfullerene small-molecule acceptors (SMAs). For instance, halogenation of the end groups in the acceptordonor-acceptor-type SMAs is an effective strategy to modulate the properties of the end group and thus the entire SMA. While previous position modulations have focused on only one substituent, this study shows the development of three isomeric SMAs (BTP-ClBr, BTP-ClBr1, and BTP-ClBr2) via manipulating the position of two halogen substituents (chlorine and bromine) on the terminal unit. BTP-ClBr exhibits a blueshifted absorption, a shallower lowest unoccupied molecular orbital energy level, and a weaker crystallization tendency relative to BTP-ClBr1 and BTP-ClBr2. A power conversion efficiency (16.82%) and an excellent fill factor (FF) (0.79) are realized in the optimal PM6:BTP-ClBr organic solar cell device. The higher FF is consistent with the results of the characterization including a longer charge recombination lifetime, a faster photocurrent decay, a weaker bimolecular recombination, and a more favorable domain size for PM6:BTP-ClBr, which all originate from a subtle change in the substitution sites that strongly influences the physicochemical properties of the SMA.

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High Efficiency Polymer Solar Cells with Efficient Hole Transfer at Zero Highest Occupied Molecular Orbital Offset between Methylated Polymer Donor and Brominated Acceptor

Cited by 354 publications

References 52 publications

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

Altering the Positions of Chlorine and Bromine Substitution on the End Group Enables High‐Performance Acceptor and Efficient Organic Solar Cells

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