High-Performance Mid-Bandgap Fused-Pyrene Electron Acceptor

Subscriber access provided by YORK UNIV

Article

High-Performance Mid-Bandgap Fused-Pyrene Electron Acceptor Guilong Cai, Peiyao Xue, Zhenyu Chen, Tengfei Li, Kuan Liu, Wei Ma, Jiarong Lian, Pengju Zeng, Yiping Wang, Ray P. S. Han, and Xiaowei Zhan Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/acs.chemmater.8b04668 • Publication Date (Web): 17 Dec 2018 Downloaded from http://pubs.acs.org on December 17, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Chemistry of Materials

High-Performance Mid-Bandgap Fused-Pyrene Electron Acceptor Guilong Cai,†,‡,§ Peiyao Xue,‡ ,§ Zhenyu Chen,⊥ Tengfei Li,‡ Kuan Liu,‡ Wei Ma,⊥ Jiarong Lian*,†, Pengju Zeng,† Yiping Wang,† Ray P.S. Han,‡ and Xiaowei Zhan*,‡ †

Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education

and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China ‡

Department of Materials Science and Engineering, College of Engineering, Key

Laboratory of Polymer Chemistry and Physics of Ministry of Education, Peking University, Beijing 100871, China

⊥

State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong

University, Xi'an 710049, China

§

Contributed equally

1 ACS Paragon Plus Environment

Chemistry of Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ABSTRACT: A new mid-bandgap nonfullerene acceptor, FPIC, is designed and synthesized based on a novel fused-pyrene electron-donating core. FPIC exhibits intense light absorption between 500 and 750 nm, with a maximum molar extinction coefficient of 2.3 × 105 M–1 cm–1 at 645 nm, a medium optical bandgap of 1.63 eV, as well as a high electron mobility of 1.7 × 10–3 cm2 V–1 s–1. The ternary-blend organic solar cells (OSCs) composing of low-bandgap donor PTB7-Th, ultranarrow-bandgap nonfullerene acceptor F8IC and FPIC yield a high power conversion efficiency (PCE) of 13.0%, significantly surpassing the PCE value of the PTB7-Th/F8IC binary-blend OSCs (9.55%). The ternary blend exhibits complementary absorption, effective exciton dissociation, balanced charge transport and reduced charge recombination, leading to the improvement in open-circuit voltage, short-circuit current density and fill factor, relative to PTB7-Th/F8IC counterpart. This work indicates that the mid-bandgap fused-pyrene electron acceptor FPIC is a promising third component to enhance photovoltaic performance of low-bandgap donor/acceptor binary blends.


Page 2 of 24

Page 3 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1. INTRODUCTION Compared with silicon-based solar cells, organic solar cells (OSCs) have unique merits, such as low cost, light weight, environmental friendliness, as well as easy fabrication into semi-transparent, mechanically flexible and large-area devices, therefore are attracting intense attention from the academic and industrial communities.1-3 Recently, most significant developments in OSCs have focused on nonfullerene acceptors (NFAs). Compared with traditional fullerene-based acceptors, NFAs have tunable molecular energy levels, strong and broad optical absorption in visible and near-infrared (NIR) region, and good morphological stability.4-6 Since 2015, when we reported the star molecule ITIC7 and its derivative IEIC,8 we developed a family of high-performance NFAs named "fused-ring electron acceptor (FREA)". Generally, FREAs possess a linear acceptor–donor–acceptor structure

consisting

of

one

electron-donating

fused-ring

core

(e.g.,

indaceno[3,2-b]dithiophene (IDT), indacenodithieno[3,2-b]thiophene (IDTT)) and two electron-accepting end-caps (e.g., 1,1-dicyanomethylene-3-indanone (IC)). The ITIC family offers the advantages of easy molecular tailoring, facile manipulation of electronic properties, wide and intense absorption in visible-NIR region and high electron mobility.9-17 Extensive works have been carried out to modify electron-rich cores,10-14,

18, 19

side chains16,

17, 20, 21

and electron-withdrawing end groups22-25 to

optimize the molecular structures. The discovery of ITIC is pushing this field to a higher horizon; power conversion efficiencies (PCEs) of 13-14% have been realized for FREA-based single-junction devices,26-29 exceeding the best-performance



fullerene-based devices (11-12%). Most high-performance FREAs generally have narrow bandgaps (1.2-1.6 eV) with absorption edge around 800-1000 nm.30-32 However, mid- and wide-bandgap FREAs with bandgap > 1.6 eV have been rarely reported, although they are desired for tandem4, 33 and ternary34-37 OSCs. In this work, we report a novel mid-bandgap FREA, FPIC (Figure 1a), based on a new fused-10-ring core, where pyrene is condensed with two thieno[3,2-b]thiophene via two cyclopentadienyl rings. Pyrene has a highly planar structure, good thermal stability,38 deep highest occupied molecular orbital (HOMO),39 and high charge mobility,40 and is thus widely used in the synthesis of organic semiconductors. Inspired by our previous work where we discovered that replacing the central benzene unit in IDT by naphthalene leads to blue-shifted absorption of FREA,41 to blue-shift absorption of narrow-bandgap ITIC, we replace the central benzene unit in IDTT using pyrene. Moreover, to improve electron mobility, we replace IC end-groups in ITIC using difluorinated IC (2FIC) since we discovered that replacing IC by 2FIC leads to higher electron mobility of FREA.24 Thus, we synthesized FPIC using pyrene-based core and 2FIC end-groups. FPIC exhibits medium optical bandgap (Eg) of 1.63 eV and high electron mobility (μe) of 1.7 × 10–3 cm2 V–1 s–1. Relative to ITIC,7 FPIC exhibits 36 nm blue-shifted absorption and 6-fold higher μe. We utilized a common low-bandgap polymer donor PTB7-Th42, our previously reported ultranarrow-bandgap acceptor F8IC43 and FPIC to fabricate ternary OSCs. The optimized ternary OSCs exhibit a champion PCE of 13.0%, a factor of 36% improvement relative to that of PTB7-Th/F8IC devices (9.55%). 4 ACS Paragon Plus Environment

Page 4 of 24

Page 5 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2. RESULTS AND DISCUSSION 2.1. Synthesis and Characterization The synthetic route to FPIC is illustrated in Scheme S1. The chemical structures of intermediates and final product were characterized by 1H and

13C

NMR, mass

spectra (MS), and elemental analysis (see Supporting Information). FPIC is soluble in chloroform, chlorobenzene, o-dichlorobenzene, etc. FPIC has excellent thermal stability and its decomposition temperature (5% weight loss) is 340 C from thermogravimetric analysis (TGA) (Figure S1). From the ultraviolet-visible absorption spectra (Figure S2), FPIC in dilute chloroform solution (10–6 M) displays intense light absorption between 450 and 700 nm. The molar extinction coefficient is 2.3 × 105 M–1 cm–1 peaked at 645 nm. FPIC solid film shows a red-shifted absorption peak at 666 nm compared with that in solution and the Eg of FPIC is calculated to be 1.63 eV from the absorption edge at 760 nm (Figure 1b). We used cyclic voltammetry (CV) to study the electrochemistry of FPIC (Figure S3). The HOMO and lowest unoccupied molecular orbital (LUMO) energies of FPIC are estimated as –5.75 eV and –3.97 eV, respectively (Figure 1c). The μe of FPIC calculated by space-charge-limited-current (SCLC) method is 1.7 × 10–3 cm2 V–1 s–1 (Figure S4).

2.2. Photovoltaic Cells We adopted the inverted device architecture composing of indium tin oxide (ITO) glass/ZnO/donor:acceptor/MoO3/Ag to fabricate bulk heterojunction (BHJ) OSCs. 5 ACS Paragon Plus Environment


Page 6 of 24

The classical low-bandgap PTB7-Th was used as electron donor to blend with FPIC for the following reasons. The HOMO and LUMO energy levels of PTB7-Th are -5.20 eV and -3.59 eV, which are 0.55 eV and 0.38 eV higher than those of FPIC, respectively, ensuring efficient exciton splitting. PTB7-Th exhibits a high hole mobility (μh) of 1.2 × 10–3 cm2 V–1 s–1.44 Comparable μh and μe facilitate efficient charge

transport

and

reduce

charge

recombination

in

devices.

The

PTB7-Th(donor)/FPIC(acceptor) weight ratio is optimized to be 1/2. To optimize blend film morphology and enhance device performance, solvent additive, diphenyl ether (DPE), was employed (Table S1). The optimized PTB7-Th/FPIC device yields a PCE of 8.45% with an open-circuit voltage (VOC) of 0.755 V, a short-circuit current density (JSC) of 15.3 mA cm–2 and a fill factor (FF) as high as 73.1%. Light absorption region overlapping between PTB7-Th and FPIC limits JSC. To extend absorption and improve JSC, F8IC was introduced as the second acceptor into PTB7-Th/FPIC binary system for the following reasons: 1) both FPIC and F8IC have 2FIC units, which enables good compatibility when blended with each other; 2) F8IC efficiently absorbs light in 700-1000 nm, leading to panchromatic absorption and increase in JSC. The weight ratio of donor/acceptors is 1/2, same as the PTB7-Th/FPIC devices. When the content of F8IC in acceptors increases from 0% to 100%, the VOC linearly decreases from 0.755 to 0.645 V (Figure S5), due to the lower LUMO of F8IC; JSC and FF increase and then decrease (Figure S6, Table S2). When F8IC is 50 wt% in acceptors, ternary devices afford a champion PCE of 13.0%, a VOC of 0.694 V, a JSC of 26.3 mA cm–2 and a FF of 71.0% (Figure 2a, Table 1). 6 ACS Paragon Plus Environment

Page 7 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Compared with PTB7-Th/FPIC binary device, the PTB7-Th/FPIC/F8IC ternary device yields a significantly higher JSC, due to panchromatic absorption complemented by F8IC in 750-1000 nm region. Compared with PTB7-Th/F8IC binary device, ternary device affords higher VOC, JSC and FF, and the PCE value is improved by a factor of 54% and 36%, respectively, relative to that of PTB7-Th/FPIC and PTB7-Th/F8IC counterparts. The external quantum efficiency (EQE) spectra of binary and ternary devices are given in Figure 2b. The JSC calculated from integration of EQE of all the devices is similar to that measured by J-V curves (< 5% mismatch). The high EQE at 350-450 nm of PTB7-Th/FPIC binary device is attributed to strong absorption of FPIC, while the high EQE at 800-1000 nm of PTB7-Th/F8IC binary device is benefited from strong absorption of F8IC. For PTB7-Th/FPIC/F8IC device, the EQE value shows improvement in the whole region, accounting for the improvement of JSC. The overlapping between photoluminescence (PL) spectra of FPIC and absorption spectra of F8IC (Figure S7a) implies that energy transfer from FPIC to F8IC is possible. FPIC and F8IC pure films as well as FPIC/F8IC (1/1, w/w) blend film were excited at 616 nm to measure their emission spectra (Figure S7b). The emission peaks of FPIC and F8IC pure films are located at ~ 740 nm and ~ 960 nm, respectively. The FPIC/F8IC blend film exhibits an enhanced emission, while the emission from FPIC disappears, indicating the energy transfer from FPIC to F8IC. Interestingly, the blend exhibits an emission peak at ~ 930 nm, different from pure F8IC or FPIC, implying a new state (alloy) existing in the blend.45, 46 7 ACS Paragon Plus Environment


The exciton dissociation and charge generation behaviors in devices were investigated by measuring the relationship between photocurrent density (Jph) and effective voltage (Veff) (Figure 2c). When Veff is larger than 2 V, all excitons are effectively split into holes and electrons and transported to electrodes; Jph reaches saturation state (Jsat). JSC/Jsat characterizes the charge dissociation probability. JSC/Jsat for the PTB7-Th/FPIC, PTB7-Th/F8IC and PTB7-Th/FPIC/F8IC devices are 98.0%, 96.1% and 97.0%, respectively, indicating effective charge dissociation in all these devices. The relation between JSC and incident light intensity (Plight) reflects the bimolecular recombination in BHJ OSCs (Figure 2d). The JSC and Plight comply with a power-law formula, JSC ∝ Plightα. When α is equal to 1, all free charges are effectively gathered by electrodes prior to bimolecular recombination. The α values are 0.973, 0.960, 0.961 for PTB7-Th/FPIC, PTB7-Th/F8IC and PTB7-Th/FPIC/F8IC OSCs, respectively, suggesting negligible bimolecular recombination in all the devices.47, 48 The charge transport properties of the blends were investigated using SCLC method (Table S3, Figure S8).49 PTB7-Th/FPIC binary blend exhibits highest μh and μe with most balanced charge transport, leading to the highest FF. PTB7-Th/F8IC binary blend exhibits lowest μh and μe with unbalanced charge transport, accounting for its lowest FF. PTB7-Th/FPIC/F8IC device exhibits higher μh and μe with more balanced charge transport, which is beneficial to its higher FF in comparison with PTB7-Th/F8IC binary blend. 8 ACS Paragon Plus Environment

Page 8 of 24

Page 9 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2.3. Film Morphology Atomic force microscope (AFM) was employed to image the active layer surface morphology (Figure S9). The PTB7-Th/FPIC and PTB7-Th/F8IC films present smooth surface with root-mean square (RMS) roughness of 1.76 nm and 1.48 nm, respectively. The ternary blend film exhibits clear aggregation domains with larger RMS roughness of 2.12 nm. Grazing incidence wide-angle X-ray scattering (GIWAXS) was employed to study the molecular packing in films.50 GIWAXS images of three neat films of donor and acceptors are presented in Figure S10. PTB7-Th pure film exhibits broad scattering pattern in the out-of-plane direction corresponding to π-π stacking peak (q = 1.58 Å-1, d-spacing = 3.98 Å), while π-π stacking peaks of both F8IC and FPIC are located at q = 1.75 Å-1 (d-spacing = 3.60 Å). The (100) coherence length of two acceptors F8IC and FPIC were 32(±1.6) and 84(±0.6) Å, respectively, indicating that FPIC has higher crystallinity. Figure 3 shows GIWAXS two-dimensional (2D) patterns of the blend films as well as their corresponding line cuts. It is found that the PTB7-Th/FPIC blend is more ordered than the PTB7-Th/F8IC blend, mainly owing to FPIC high crystallinity. In the ternary blend, the highly ordered structure of PTB7-Th/FPIC is preserved, and thus the high FF is achieved. Further quantitative analysis is carried out to probe the detailed molecular stacking. The π-π stacking (010) coherence length of donor in PTB7-Th/FPIC, PTB7-Th/F8IC and PTB7-Th/F8IC/FPIC is 12(±0.3), 10(±0.1), 9(±0.3) Å, and the (010) coherence length of acceptor is 21(±0.4), 20(±0.4), 25(±0.4) Å, respectively. This confirms that the 9 ACS Paragon Plus Environment


crystallinity of acceptors in the ternary blend is enhanced. Resonant soft X-ray scattering (R-SoXS) was used to study the phase separation of the blends (Figure 4).51, 52 The photo energy of 284.8 eV was adopted to acquire highly enhanced materials contrast. The long period (domain size) and domain purity can be extracted from the R-SoXS profiles (Table S4). The PTB7-Th/FPIC blend shows the highest phase purity; higher purity is beneficial to reducing charge recombination as well as improving charge transport, which leads to the highest FF. The PTB7-Th/F8IC system has a smaller domain size and smaller purity, which is favorable to charge separation but unfavorable to charge transport, leading to a lower FF though it remains a high JSC. The PBT7-Th/FPIC/F8IC ternary blend has only slightly decreased purity compared with PTB7-Th/FPIC binary blend, which is beneficial to charge transport. Meanwhile, the ternary system has appropriate domain size. These two factors lead to simultaneously increased FF and JSC in ternary system. 3. CONCLUSION In summary, a mid-bandgap nonfullerene acceptor FPIC has been synthesized using a novel fused-pyrene as electron-donating building block. FPIC exhibits excellent thermal stability, intense light absorption in ca. 500-700 nm, and high electron mobility. PTB7-Th/FPIC/F8IC ternary devices yield a high PCE of 13.0%, significantly surpassing that of PTB7-Th/FPIC (8.45%) and PTB7-Th/F8IC (9.55%) counterparts. The ternary blend exhibits complementary absorption, effective exciton dissociation, balanced charge transport and reduced charge recombination, leading to synergistic improvement in VOC, JSC and FF, relative to PTB7-Th/F8IC counterpart. 10 ACS Paragon Plus Environment

Page 10 of 24

Page 11 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


These results demonstrate that the mid-bandgap fused-pyrene electron acceptor FPIC is a promising third component to enhance the device performance of low-bandgap donor/acceptor blends. ASSOCIATED CONTENT Supporting Information. This material is available free of charge via the Internet at http://pubs.acs.org. Materials synthesis and characterization; TGA curve, SCLC, AFM images, GIWAXS and R-SoXS data; device fabrication, optimization and characterization. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] (X.Z.). *E-mail: [email protected] (J.L.). Notes The authors declare no competing financial interest. ACKNOWLEDGMENT X.Z. thanks the NSFC (Nos. 21734001 and 51761165023). W.M. thanks for the support from Ministry of Science and Technology (No. 2016YFA0200700), NSFC (Nos. 21875182 and 21534003). X-ray data was acquired at beamlines 7.3.3 and 11.0.1.2 at the Advanced Light Source, which is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The authors thank Chenhui Zhu at beamline 7.3.3, and Cheng Wang at beamline 11.0.1.2 for assistance with data acquisition. 11 ACS Paragon Plus Environment


REFERENCES (1) Li, G.; Zhu, R.; Yang, Y. Polymer Solar Cells. Nat. Photon. 2012, 6, 153-161. (2) Lin, Y.; Li, Y.; Zhan, X. Small Molecule Semiconductors for High-Efficiency Organic Photovoltaics. Chem. Soc. Rev. 2012, 41, 4245-4272. (3) Lu, L.; Zheng, T.; Wu, Q.; Schneider, A. M.; Zhao, D.; Yu, L. Recent Advances in Bulk Heterojunction Polymer Solar Cells. Chem. Rev. 2015, 115, 12666-12731. (4) Cheng, P.; Li, G.; Zhan, X.; Yang, Y. Next-Generation Organic Photovoltaics Based on Non-fullerene Acceptors. Nat. Photon. 2018, 12, 131-142. (5) Yan, C.; Barlow, S.; Wang, Z.; Yan, H.; Jen, A. K. Y.; Marder, S. R.; Zhan, X. Non-fullerene Acceptors for Organic Solar Cells. Nat. Rev. Mater. 2018, 3, 18003. (6) Zhao, J.; Li, Y.; Yang, G.; Jiang, K.; Lin, H.; Ade, H.; Ma, W.; Yan, H. Efficient Organic Solar Cells Processed From Hydrocarbon Solvents. Nat. Energy 2016, 1, 15027. (7) Lin, Y.; Wang, J.; Zhang, Z. G.; Bai, H.; Li, Y.; Zhu, D.; Zhan, X. An Electron Acceptor Challenging Fullerenes for Efficient Polymer Solar Cells. Adv. Mater. 2015, 27, 1170-1174. (8) Lin, Y.; Zhang, Z. G.; Bai, H.; Wang, J.; Yao, Y.; Li, Y.; Zhu, D.; Zhan, X. High-performance Fullerene-free Polymer Solar Cells with 6.31% Efficiency. Energy Environ. Sci. 2015, 8, 610-616. (9) Lin, Y.; Li, T.; Zhao, F.; Han, L.; Wang, Z.; Wu, Y.; He, Q.; Wang, J.; Huo, L.; Sun, Y.; Wang, C.; Ma, W.; Zhan, X. Structure Evolution of Oligomer Fused-Ring Electron Acceptors toward High Efficiency of As-Cast Polymer Solar Cells. Adv. 12 ACS Paragon Plus Environment

Page 12 of 24

Page 13 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Energy Mater. 2016, 6, 1600854. (10) Wang, J.; Zhang, J.; Xiao, Y.; Xiao, T.; Zhu, R.; Yan, C.; Fu, Y.; Lu, G.; Lu, X.; Marder, S. R.; Zhan, X. Effect of Isomerization on High-Performance Nonfullerene Electron Acceptors. J. Am. Chem. Soc. 2018, 140, 9140-9147. (11) Li, T.; Dai, S.; Ke, Z.; Yang, L.; Wang, J.; Yan, C.; Ma, W.; Zhan, X. Fused Tris(thienothiophene)-Based Electron Acceptor with Strong Near-Infrared Absorption for High-Performance As-Cast Solar Cells. Adv. Mater. 2018, 30, 1705969. (12) Zhu, J.; Ke, Z.; Zhang, Q.; Wang, J.; Dai, S.; Wu, Y.; Xu, Y.; Lin, Y.; Ma, W.; You, W.; Zhan, X. Naphthodithiophene-Based Nonfullerene Acceptor for High-Performance Organic Photovoltaics: Effect of Extended Conjugation. Adv. Mater. 2018, 30, 1704713. (13) Wang, W.; Yan, C.; Lau, T. K.; Wang, J.; Liu, K.; Fan, Y.; Lu, X.; Zhan, X. Fused Hexacyclic Nonfullerene Acceptor with Strong Near-Infrared Absorption for Semitransparent Organic Solar Cells with 9.77% Efficiency. Adv. Mater. 2017, 29, 1701308. (14) Wang, J.; Wang, W.; Wang, X.; Wu, Y.; Zhang, Q.; Yan, C.; Ma, W.; You, W.; Zhan, X. Enhancing Performance of Nonfullerene Acceptors via Side-Chain Conjugation Strategy. Adv. Mater. 2017, 29, 1702125. (15) Zhao, F.; Dai, S.; Wu, Y.; Zhang, Q.; Wang, J.; Jiang, L.; Ling, Q.; Wei, Z.; Ma, W.; You, W.; Wang, C.; Zhan, X. Single-Junction Binary-Blend Nonfullerene Polymer Solar Cells with 12.1% Efficiency. Adv. Mater. 2017, 29, 1700144. (16) Lin, Y.; Zhao, F.; He, Q.; Huo, L.; Wu, Y.; Parker, T. C.; Ma, W.; Sun, Y.; 13 ACS Paragon Plus Environment


Wang, C.; Zhu, D.; Heeger, A. J.; Marder, S. R.; Zhan, X. High-Performance Electron Acceptor with Thienyl Side Chains for Organic Photovoltaics. J. Am. Chem. Soc. 2016, 138, 4955-4961. (17) Lin, Y.; He, Q.; Zhao, F.; Huo, L.; Mai, J.; Lu, X.; Su, C. J.; Li, T.; Wang, J.; Zhu, J.; Sun, Y.; Wang, C.; Zhan, X. A Facile Planar Fused-Ring Electron Acceptor for As-Cast Polymer Solar Cells with 8.71% Efficiency. J. Am. Chem. Soc. 2016, 138, 2973-2976. (18) Jia, B.; Dai, S.; Ke, Z.; Yan, C.; Ma, W.; Zhan, X. Breaking 10% Efficiency in Semitransparent Solar Cells with Fused-Undecacyclic Electron Acceptor. Chem. Mater. 2017, 30, 239-245. (19) Kan, B.; Feng, H.; Wan, X.; Liu, F.; Ke, X.; Wang, Y.; Wang, Y.; Zhang, H.; Li, C.; Hou, J.; Chen, Y. Small-Molecule Acceptor Based on the Heptacyclic Benzodi (cyclopentadithiophene) Unit for Highly Efficient Nonfullerene Organic Solar Cells. J. Am. Chem. Soc. 2017, 139, 4929-4934. (20) Yang, Y.; Zhang, Z. G.; Bin, H.; Chen, S.; Gao, L.; Xue, L.; Yang, C.; Li, Y. Side-Chain Isomerization on an n-type Organic Semiconductor ITIC Acceptor Makes 11.77% High Efficiency Polymer Solar Cells. J. Am. Chem. Soc. 2016, 138, 15011-15018. (21) Cheng, P.; Wang, J.; Zhang, Q.; Huang, W.; Zhu, J.; Wang, R.; Chang, S. Y.; Sun, P.; Meng, L.; Zhao, H.; Cheng, H. W.; Huang, T.; Liu, Y.; Wang, C.; Zhu, C.; You, W.; Zhan, X.; Yang, Y. Unique Energy Alignments of a Ternary Material System toward High-Performance Organic Photovoltaics. Adv. Mater. 2018, 30, 14 ACS Paragon Plus Environment

Page 14 of 24

Page 15 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1801501. (22) Zhang, M.; Gao, W.; Zhang, F.; Mi, Y.; Wang, W.; An, Q.; Wang, J.; Ma, X.; Miao, J.; Hu, Z.; Liu, X.; Zhang, J.; Yang, C. Efficient Ternary Non-fullerene Polymer Solar Cells with PCE of 11.92% and FF of 76.5%. Energy Environ. Sci. 2018, 11, 841-849. (23) Wang, Y.; Zhang, Y.; Qiu, N.; Feng, H.; Gao, H.; Kan, B.; Ma, Y.; Li, C.; Wan, X.; Chen, Y. A Halogenation Strategy for over 12% Efficiency Nonfullerene Organic Solar Cells. Adv. Energy Mater. 2018, 8, 1702870. (24) Dai, S.; Zhao, F.; Zhang, Q.; Lau, T. K.; Li, T.; Liu, K.; Ling, Q.; Wang, C.; Lu, X.; You, W.; Zhan, X. Fused Nonacyclic Electron Acceptors for Efficient Polymer Solar Cells. J. Am. Chem. Soc. 2017, 139, 1336-1343. (25) Luo, Z.; Bin, H.; Liu, T.; Zhang, Z. G.; Yang, Y.; Zhong, C.; Qiu, B.; Li, G.; Gao, W.; Xie, D.; Wu, K.; Sun, Y.; Liu, F.; Li, Y.; Yang, C. Fine-Tuning of Molecular Packing and Energy Level through Methyl Substitution Enabling Excellent Small Molecule Acceptors for Nonfullerene Polymer Solar Cells with Efficiency up to 12.54. Adv. Mater. 2018, 30, 1706124. (26) Zhang, H.; Yao, H.; Hou, J.; Zhu, J.; Zhang, J.; Li, W.; Yu, R.; Gao, B.; Zhang, S.; Hou, J. Over 14% Efficiency in Organic Solar Cells Enabled by Chlorinated Nonfullerene Small-Molecule Acceptors. Adv. Mater. 2018, 30, 1800613. (27) Zhang, Y.; Kan, B.; Sun, Y.; Wang, Y.; Xia, R.; Ke, X.; Yi, Y. Q. Q.; Li, C.; Yip, H. L.; Wan, X.; Cao, Y.; Chen, Y. Nonfullerene Tandem Organic Solar Cells with High Performance of 14.11. Adv. Mater. 2018, 30, 1707508. 15 ACS Paragon Plus Environment


(28) Zheng, Z.; Hu, Q.; Zhang, S.; Zhang, D.; Wang, J.; Xie, S.; Wang, R.; Qin, Y.; Li, W.; Hong, L.; Liang, N.; Liu, F.; Zhang, Y.; Wei, Z.; Tang, Z.; Russell, T. P.; Hou, J.; Zhou, H. A Highly Efficient Non-fullerene Organic Solar Cell with a Fill Factor over 0.80 Enabled by a Fine-Tuned Hole-Transporting Layer. Adv. Mater. 2018, 1801801. (29) Chen, J. D.; Li, Y. Q.; Zhu, J.; Zhang, Q.; Xu, R. P.; Li, C.; Zhang, Y. X.; Huang, J. S.; Zhan, X.; You, W.; Tang, J. X. Polymer Solar Cells with 90% External Quantum Efficiency Featuring an Ideal Light- and Charge-Manipulation Layer. Adv. Mater. 2018, 30, 1706083. (30) Xiao, Z.; Jia, X.; Ding, L. Ternary Organic Solar Cells Offer 14% Power Conversion Efficiency. Sci. Bull. 2017, 62, 1562-1564. (31) Yao, Z.; Liao, X.; Gao, K.; Lin, F.; Xu, X.; Shi, X.; Zuo, L.; Liu, F.; Chen, Y.; Jen, A. K. Y. Dithienopicenocarbazole-Based Acceptors for Efficient Organic Solar Cells with Optoelectronic Response Over 1000 nm and an Extremely Low Energy Loss. J. Am. Chem. Soc. 2018, 140, 2054-2057. (32) Yao, H.; Cui, Y.; Yu, R.; Gao, B.; Zhang, H.; Hou, J. Design, Synthesis, and Photovoltaic Characterization of a Small Molecular Acceptor with an Ultra-Narrow Band Gap. Angew. Chem. Int. Ed. 2017, 56, 3045-3049. (33) Meng, L.; Zhang, Y.; Wan, X.; Li, C.; Zhang, X.; Wang, Y.; Ke, X.; Xiao, Z.; Ding, L.; Xia, R.; Yip, H. L.; Cao, Y.; Chen, Y. Organic and Solution-processed Tandem Solar Cells with 17.3% Efficiency. Science 2018, 361, 1094-1098. (34) Baran, D.; Ashraf, R. S.; Hanifi, D. A.; Abdelsamie, M.; Gasparini, N.; Röhr, J. 16 ACS Paragon Plus Environment

Page 16 of 24

Page 17 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


A.; Holliday, S.; Wadsworth, A.; Lockett, S.; Neophytou, M.; Emmott, C. J.; Nelson, J.; Brabec, C. J.; Amassian, A.; Salleo, A.; Kirchartz, T.; Durrant, J. R.; McCulloch, I. Reducing the Efficiency-Stability-Cost Gap of Organic Photovoltaics with Highly Efficient and Stable Small Molecule Acceptor Ternary Solar Cells. Nat. Mater. 2017, 16, 363-369. (35) Lu, L.; Kelly, M. A.; You, W.; Yu, L. Status and Prospects for Ternary Organic Photovoltaics. Nat. Photon. 2015, 9, 491. (36) Liu, T.; Guo, Y.; Yi, Y.; Huo, L.; Xue, X.; Sun, X.; Fu, H.; Xiong, W.; Meng, D.; Wang, Z.; Liu, F.; Russell, T. P.; Sun, Y. Ternary Organic Solar Cells Based on Two Compatible Nonfullerene Acceptors with Power Conversion Efficiency >10. Adv. Mater. 2016, 28, 10008-10015. (37) Zhang, J.; Yan, C.; Wang, W.; Xiao, Y.; Lu, X.; Barlow, S.; Parker, T. C.; Zhan, X.; Marder, S. R. Panchromatic Ternary Photovoltaic Cells Using a Nonfullerene Acceptor Synthesized Using C–H Functionalization. Chem. Mater. 2018, 30, 309-313. (38) Figueira-Duarte, T. M.; Müllen, K. Pyrene-Based Materials for Organic Electronics. Chem. Rev. 2011, 111, 7260-7314. (39) Zöphel, L.; Beckmann, D.; Enkelmann, V.; Chercka, D.; Rieger, R.; Müllen, K. Asymmetric Pyrene Derivatives for Organic Field-Effect Transistors. Chem. Commun. 2011, 47, 6960-6962. (40) Liu, S. Y.; Liu, W. Q.; Xu, J. Q.; Fan, C. C.; Fu, W. F.; Ling, J.; Wu, J. Y.; Shi, M. M.; Jen, A. K. Y.; Chen, H. Z. Pyrene and Diketopyrrolopyrrole-Based Oligomers 17 ACS Paragon Plus Environment


Synthesized via Direct Arylation for OSC Applications. ACS Appl. Mater. Interfaces 2014, 6, 6765-6775. (41) Zhu, J.; Wu, Y.; Rech, J.; Wang, J.; Liu, K.; Li, T.; Lin, Y.; Ma, W.; You, W.; Zhan, X. Enhancing the Performance of a Fused-Ring Electron Acceptor via Extending Benzene to Naphthalene. J. Mater. Chem. C 2018, 6, 66-71. (42) Liao, S. H.; Jhuo, H. J.; Cheng, Y. S.; Chen, S. A. Fullerene Derivative-Doped Zinc Oxide Nanofilm as the Cathode of Inverted Polymer Solar Cells with Low-Bandgap Polymer (PTB7-Th) for High Performance. Adv. Mater. 2013, 25, 4766-4771. (43) Dai, S.; Li, T.; Wang, W.; Xiao, Y.; Lau, T. K.; Li, Z.; Liu, K.; Lu, X.; Zhan, X. Enhancing the Performance of Polymer Solar Cells via Core Engineering of NIR-Absorbing Electron Acceptors. Adv. Mater. 2018, 30, 1706571. (44) Zhu, J.; Xiao, Y.; Wang, J.; Liu, K.; Jiang, H.; Lin, Y.; Lu, X.; Zhan, X. Alkoxy-Induced Near-Infrared Sensitive Electron Acceptor for High-Performance Organic Solar Cells. Chem. Mater. 2018, 30, 4150-4156. (45) Khlyabich, P. P.; Burkhart, B.; Thompson, B. C. Efficient Ternary Blend Bulk Heterojunction Solar Cells with Tunable Open-Circuit Voltage. J. Am. Chem. Soc. 2011, 133, 14534-14537. (46) Cheng, P.; Yan, C.; Wu, Y.; Wang, J.; Qin, M.; An, Q.; Cao, J.; Huo, L.; Zhang, F.; Ding, L.; Sun, Y.; Ma, W.; Zhan, X. Alloy Acceptor: Superior Alternative to PCBM toward Efficient and Stable Organic Solar Cells. Adv. Mater. 2016, 28, 8021-8028. 18 ACS Paragon Plus Environment

Page 18 of 24

Page 19 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(47) Schilinsky, P.; Waldauf, C.; Brabec, C. J. Recombination and Loss Analysis in Polythiophene Based Bulk Heterojunction Photodetectors. Appl. Phys. Lett. 2002, 81, 3885-3887. (48) Street, R. A.; Schoendorf, M.; Roy, A.; Lee, J. H. Interface State Recombination in Organic Solar Cells. Phys. Rev. B 2010, 81, 205307. (49) Malliaras, G. G.; Salem, J. R.; Brock, P. J.; Scott, C. Electrical Characteristics and Efficiency of Single-Layer Organic Light-Emitting Diodes. Physical Review B 1998, 58, 13411. (50) Hexemer, A.; Bras, W.; Glossinger, J.; Schaible, E.; Gann, E.; Kirian, R.; MacDowell, A.; Church, M.; Rude, B.; Padmore, H. A SAXS/WAXS/GISAXS Beamline with Multilayer Monochromator. J. Phys. Conf. Ser. 2010, 247, 012007. (51) Gann, E.; Young, A. T.; Collins, B. A.; Yan, H.; Nasiatka, J.; Padmore, H. A.; Ade, H.; Hexemer, A.; Wang, C. Soft X-Ray Scattering Facility at the Advanced Light Source with Real-Time Data Processing and Analysis. Rev. Sci. Instrum. 2012, 83, 045110. (52) Wu, Y.; Wang, Z.; Meng, X.; Ma, W. Morphology Analysis of Organic Solar Cells with Synchrotron Radiation Based Resonant Soft X-Ray Scattering. Prog. Chem. 2017, 29, 93-101.



Donor

Acceptor

(a)

NC

S R O

F

F

S

CN

R

R

CN

F

S O

S

R R

F

S

S

n

S F C4 H9

O S

S

C4 H9 F

S

S

R R

S

S

CN

F

NC

C2 H5 C4 H9

NC

S

S

C2 H5

O O

O S

R

F

F

FPIC

CN

C2 H5

PTB7-Th

NC

F8IC R=

C6H13

(b)

(c)

0.4 0.2 0.0 300

LUMO -3.97

-4.06

F8IC

0.6

-3.59

FPIC

0.8

PTB7-Th FPIC F8IC

PTB7-Th

1.0

Energy level (eV)

Normalized absorbance (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 24

-5.20 -5.47

-5.75

450

600

750

900

1050

HOMO

Wavelength (nm)

Figure 1. (a) Molecular structures, (b) UV-vis absorption spectra, and (c) energy levels diagram of FPIC, F8IC and PTB7-Th.


Page 21 of 24

(b)

5

80

0

PTB7-Th/FPIC PTB7-Th/F8IC PTB7-Th/FPIC/F8IC

-5 -10

EQE (%)

Current density (mA cm-2)

(a)

-15 -20

40 20

-25 -30

60

0.0

0.2

0.4

0.6

0 300

0.8


450

Voltage (V)

600

750

900

1050

Wavelength (nm)

(c)

(d) 10

JSC (mA cm-2)

Jph (mA cm-2)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1 PTB7-Th/FPIC PTB7-Th/F8IC PTB7-Th/FPIC/F8IC

0.1

0.1

Veff (V)

10


1 10

1

100

Light intensity (mW cm-2)

Figure 2. (a) J-V characteristics and (b) EQE spectra of optimized OSCs under illumination of an AM 1.5G at 100 mW cm–2. (c) Jph versus Veff and (d) JSC versus light intensity of the optimized devices.



Figure 3. 2D GIWAXS patterns of (a) PTB7-Th/FPIC, (b) PTB7-Th/F8IC and (c) PTB7-Th/FPIC/F8IC; (d) their corresponding line cuts.


Page 22 of 24

Page 23 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. R-SoXS profiles of the blend films.

Table 1. Performance of the optimized OSCs based on PTB7-Th/acceptors.a VOC

JSC

FF

PCE

calc JSC

(V)

(mA cm–2)

(%)

(%)

(mA cm–2)

0.755

15.3

73.1

8.45

15.1

(0.753±0.003)

(15.4±0.3)

(71.5±1.4)

(8.29±0.16)

0.645

23.3

63.4

9.55

(0.648±0.003)

(23.3±0.9)

(62.7±0.7)

(9.47±0.16)

0.694

26.3

71.0

13.0

(0.687±0.006)

(26.7±0.8)

(69.6±1.6)

(12.7±0.3)

acceptor

FPIC

F8IC

FPIC/F8IC

a

Average values (in parenthesis) are obtained from 20 devices.


23.4

25.0


Table of Contents


Page 24 of 24

High-Performance Mid-Bandgap Fused-Pyrene Electron Acceptor

Recommend Documents