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Thieno[3,2-b]pyrrolo Fused Pentacyclic Benzotriazole Based Acceptor for Efficient Organic Photovoltaics Liuliu Feng, Jun Yuan, Zhenzhen Zhang, Hongjian Peng, ZhiGuo Zhang, Shutao Xu, Ye Liu, Yongfang Li, and Yingping Zou ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b10995 • Publication Date (Web): 24 Aug 2017 Downloaded from http://pubs.acs.org on August 25, 2017

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ACS Applied Materials & Interfaces

Thieno[3,2-b]pyrrolo Fused Pentacyclic Benzotriazole Based Acceptor for Efficient Organic Photovoltaics Liuliu Feng†§, Jun Yuan†§, Zhenzhen Zhang†, Hongjian Peng†, Zhi-Guo Zhang‡, Shutao Xu†, Ye Liu†, Yongfang Li‡, Yingping Zou*† †

College of Chemistry and Chemical Engineering, Central South University, Changsha 410083,

China. ‡

Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy

of Sciences, Beijing 100190, China. §

Liuliu Feng and Jun Yuan contributed this work equally.

ABSTRACT A novel non-fullerene small molecular acceptor (BZIC) based on a ladder-type thieno[3,2b]pyrrolo fused pentacyclic benzotriazole core (dithieno[3,2-b]pyrrolobenzotriazole, BZTP) and end-capped with 1,1-dicyanomethylene-3-indanone (INCN) has been firstly reported in this work. Through introducing multifused benzotriazole and INCN, BZIC could maintain a highlying lowest unoccupied molecular orbital (LUMO) energy level of -3.88 eV. Moreover, BZIC shows a low optical bandgap of 1.45 eV with broad and efficient absorption band from 600 to 850 nm due to increased π-π interactions by the covalently locking thiophene and benzotriazole units. A power conversion efficiency of 6.30% is delivered using BZIC as non-fullerene acceptor and our recently synthesized hexafluroquinoxaline based polymer HFQx-T as donor. This is the first time to synthesize mutifused benzotriazole based molecules as non-fullerene

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electron acceptor up to date. The preliminary results demonstrate that the mutifused benzotriazole derivatives hold great potential for efficient photovoltaics. KEYWORDS: mutifused benzotriazole, novel non-fullerene acceptor, hexafluroquinoxaline based polymer, covalently locking, efficient photovoltaics

INTRODUCTION Organic photovoltaics (OPVs) have intrigued broad interest due to the inexpensive and renewable energy sources.1-3 By using conjugated organic small molecules or polymers to directly convert solar energy into electricity, OPVs possess some features such as low cost, light weight, large-area and the capability to fabricate flexible devices.4-6 Although the efficiency of OPVs is much lower than that of inorganic solar cells, in recent decades, bulk heterojunction (BHJ) solar cells have made it possible to achieve large scale, high efficiency, flexibility and solution-processability that satisfies widespread commercialization.7-9 As for photovoltaic materials, fullerene derivatives, such as [6, 6]-phenyl C61/C71 butyric acid methyl ester (PC61BM or PC71BM) are the most typical and successful n-type materials in OPVs.10-13 Nowadays, fullerene-based PSCs with power conversion efficiencies (PCE) over 11% are reached.14-16 However, electron affinities of fullerene derivatives can't be well tuned, which limits open-circuit voltages (Voc).17-19 Additionally, fullerene derivatives like PC61BM show weak absorbance in the visible-near infrared (Vis-NIR) region and have a tendency to form crystallites in active layer. Therefore, poor light absorption limits harvesting solar radiation efficiently and large phase separation restricts exciton diffusion and transport, which will decrease short-circuit current density (Jsc).20-23 To overcome these problems, many new n-type non-fullerene materials with facile synthesis and efficient absorption have been developed rapidly in the past few years.24-43


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In an attempt to explore promising materials as non-fullerene acceptors, two key factors are as following: firstly, the materials have tunable bandgaps that can be designed to have stronger absorbance in Vis-NIR region. Such planar fused central units with a π-electron delocalization could decrease bandgap and improve π-π stacking among molecules.44 Secondly, the energy levels including highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the acceptor materials could be lower than those of corresponding donor materials for efficient exciton dissociation and charge transport, the LUMO levels ought to be upshifted to provide higher Voc.45 As typical and successful cases, indacenodithiophene (IDT),46 indacenodithieno[3,2-b]thiophene (IDTT),47 and 6,12-dihydroindeno[1,2-b]fluorene (IDF)-based fused-ring electron acceptors (FREAs)48 have attracted considerable attentions. With a careful choice of donor materials matching with FREA, the BHJ solar cells have demonstrated excellent photovoltaic performance with PCE over 10%.20 For OPV materials, the introduction of a ladder-type backbone with fused rings is an efficient strategy to improve the optoelectronic properties.49-50 Undoubtedly, acceptor-donor-acceptor (AD-A) structure, such as ITIC, can induce intramolecular charge transfer and lead to broad and strong absorbance throughout 500-800 nm with an optical bandgap (Egopt) of 1.59 eV.47 Nonetheless, it is noticed that the popular donor polymers, such as PTB7-Th, showed a low bandgap with absorption from 550 to 780 nm (Egopt ≈ 1.58 eV),51 which has a strong overlap with the typical acceptor ITIC. Hence, the design and synthesis of lower bandgap (Egopt below 1.5 eV) non-fullerene acceptors matching with low or medium bandgap polymer donors will be a new and exciting topic in OPVs especially semitransparent OPVs. Motivated by the above mentioned factors, we have designed and synthesized a novel non-fullerene n-type acceptor (BZIC, Figure


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1a) based on a ladder-type fused core -dithieno[3,2-b]pyrrolobenzotriazole (BZTP) with 1,1dicyanomethylene-3-indanone (INCN) as end-cap group that possesses the following features: i)

A stronger absorption in the Vis-NIR region (550-900 nm) can be obtained. The neighboring electron-rich donor (thiophene unit) and electron-deficient acceptor (benzotriazole unit) are covalently locked into a coplanar interfused D-A structure, which can increase the electronic interactions between the donor and acceptor unit. 52

ii)

Electron affinity and ionization potentials can be fine-tuned by introduction of the acceptor unit in multifused core. The electron deficient moiety of BZTP segment is benzotriazole, which is usually used as a relatively weak electron-withdraw building block in typical D-A polymers,53-54 this structure could maintain a high-lying LUMO energy levels.

iii)

The nitrogen atoms in the pentacyclic units can not only be used as the heteroatom bridge for covalent planarization but also allow aliphatic side chains to improve the solubility of the resultant small molecular non-fullerene acceptors.52

Indeed, our results show that the new non-fullerene acceptor BZIC exhibits a broad absorption with Egopt of 1.45 eV, appropriate electron affinity with LUMO of ca. -3.88 eV. Furthermore, polymer solar cells (PSCs) based on BZIC electron acceptor and polymer donor HFQx-T55 (Figure 1a) deliver PCEs over 6%. More importantly, as far as known, this is the first time to introduce multifused benzotriazole core to construct n-type nonfullerene acceptor.56-59 Our results highlight that introducing the multifused benzotriazole core in small molecular acceptor provides a new toolbox for developing n-type materials with extended absorption, and we also firmly believe that the higher efficiencies could be reached with further optimizations from a


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better matched donor polymer, the new multifused benzotriazole based acceptor and device modifications.

Scheme 1. Synthetic route of BZIC.

RESULTS AND DISCUSSION Material Synthesis and Characterization The general synthetic route for the BZIC is shown in Scheme 1. The detailed synthetic processes for the compounds are provided in the Supporting Information. Compound 1 was synthesized through the Stille coupling of 4,7-dibromo-2-(2-ethylhexyl)-5,6-dinitro-2Hbenzo[d][1,2,3]triazole with 2-tributylstannyl thiophene in toluene. The fused D-A-D structure compound 2 was obtained by the double intramolecular Cadogan reductive cyclization of compound 1 in the presence of triethyl phosphate. Compound 3 can be produced by the Nalkylation of compound 2 with the excess amount of 1-bromo-2-ethylhexane and potassium carbonate. The dialdehyde monomer 4 was prepared by the nucleophilic reaction as an orange solid. The desired product BZIC was then obtained by the Knoevenagel condensation of the


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dialdehyde with INCN. All intermediates were characterized by 1H nuclear magnetic resonance (1H NMR). The structure of the final small molecular acceptor BZIC was confirmed by 1H NMR, 13

C NMR and mass spectrum (MS). NMR spectra and MS of the intermediates and BZIC are

shown in Figure S1-S6. BZIC shows good solubility in common organic solvents, such as chloroform,

ortho-dichlorobenzene

and

dichloromethane

at

room

temperature.

Thermogravimetric analysis (TGA) in Figure S7 indicates BZIC has good thermal stability with a decomposition temperature of 5% weight loss at 325 oC which can meet the requirements of device fabrication.

Figure 1. (a) Chemical structures of HFQx-T and BZIC. (b) Absorption spectra of HFQx-T, BZIC and BZIC:HFQx-T in the film states. (c) Estimated energy levels of HFQx-T and BZIC from electrochemical voltammetry.


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Optical and Electrochemical Properties The absorption spectra of pure HFQx-T, BZIC and their mixture in spin-coated films are illustrated in Figure 1b, BZIC in dilute chloroform solution and solid film are presented in Figure S8. Compared to the solution, a 60 nm redshift in the BZIC thin film indicated stronger aggregation of molecular backbone and π-π interactions in the solid states (Figure S8a). The absorption onset of BZIC film located at 857 nm with 79 nm redshift compared to that of ITIC. A redshift of the absorption spectra can be reached via insertion of an internal acceptor (A) in ladder-type fused core, therefore, forced planarization by covalently fastening adjacent thiophene and benzotriazole can form fused donor-(π conjugated spacer)-acceptor-(π conjugated spacer)donor (D-π-A-π-D) conjugated structure which increases intramolecular electronic interactions.60 Meanwhile, the BZIC film absorption coefficient is 1.57×105 cm-1, which is even higher than 1.19×105 cm-1 of the typical non-fullerene acceptor ITIC film (Figure S8b). As shown in Figure 1b, BZIC demonstrates complementary absorption with that of HFQx-T donor in the range of 500-850 nm, which contributes to good light harvesting in the non-fullerene PSCs. The electrochemical properties of BZIC were measured by cyclic voltammetry (CV) in anhydrous CH3CN solutions with the ferrocene/ferrocenium (Fc/Fc+) redox couple as internal reference. As shown in Figure S9, according to the equation EHOMO/LUMO = -(4.80-E1/2, Fc/Fc++Eonset,ox/red)

(eV), HOMO and LUMO energy levels of BZIC are calculated to be -5.42 and

-3.88 eV, respectively. In comparison with ITIC, the HOMO and LUMO levels of BZIC are almost similar, and the energy values are only shifted upward by 0.06 eV (HOMO) and decreased by 0.05 eV (LUMO). As shown in Figure 1c, the LUMO energy offset between BZIC and HFQx-T is 0.31eV, which provides driving force for the exciton dissociation and the


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electron transfer from HFQx-T to BZIC.61 Although the HOMO energy offset for HFQx-T: BZIC blend are very low (0.06 eV), such a small energy offset could be sufficient from the BZIC acceptor to HFQx-T donor, confirmed by the reasonably effective quantum efficiency (EQE) values of the optimal device in the 650 to 800 nm, where it can neglect the light absorption of the polymer. The optical and electronic energy level data of the HFQx-T and BZIC are summarized in Table 1. Table 1. Optical properties and energy levels of HFQx-T and BZIC.

a

λonseta

Egfilm b

Eox/HOMOc

Ered/LUMOc

EgEC

(nm)

(eV)

(V)/(eV)

(V)/(eV)

(eV)

HFQx-T

701

1.76

1.00/-5.36

-0.79/-3.57

1.79

BZIC

857

1.45

1.06/-5.42

-0.48/-3.88

1.54

Spin coated from chloroform solution. bBandgap estimated from the onset wavelength of

optical absorption. c The HOMO and LUMO levels calculated from the cyclic voltammogram.

Photovoltaic Properties To investigate the photovoltaic performances of the non-fullerene materials, BHJ solar cells with a configuration architecture of ITO (indium tin oxide)/ PEDOT:PSS (poly(3,4ethylenedioxythiophene):poly(styrenesulfonate))/HFQx-T:BZIC/PDINO

(perylene

diimide

functionalized with amino N-oxide)/Al were fabricated. All the active layers were spin-coated from chloroform solution. We chose the medium bandgap conjugated polymer HFQx-T as the ptype donor with absorption onset of ca. 705 nm. The absorption of HFQx-T is complementary to that of the n-type acceptor (BZIC) which can broaden the absorption profile of HFQx-T:BZICbased PSCs. Figure 2a displays the current density versus voltage (J-V) characteristic curves


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under AM 1.5G, mW cm-2 and the key device parameters are summarized in Table 2. The effects of the D/A (HFQx-T/BZIC) weight ratios in the active layer on device performance were firstly studied with D/A weight ratios from 1.5:1 to 1:1.5, with the PCEs of HFQx-T:BZIC for the 1.5:1, 1:1 and 1:1.5 weight ratios reaching 2.02%, 2.52% and 3.92%, respectively. With thermal annealing (TA) at 120 oC for 10 min, the devices using 1:1.5 D/A blend ratio show slightly decreased Voc, but increased Jsc and FF, leading to a higher efficiency up to 5.23 %. Subsequently, the high boiling point processing additive 1-chloronaphthalene (CN) is used to optimize the morphology of the active layer for more efficient PSCs. We found that introducing CN treating the active layer can significantly improve the photovoltaic efficiencies. Finally, after TA at 120 oC for 10 min, HFQx-T:BZIC device delivers a moderate PCE of 6.30% with a Voc of 0.84 V, Jsc of 12.67 mA/cm2 and fill factor (FF) of 59% under 0.25% CN condition. The photovoltaic performance of HFQx-T/BZIC with various weight ratios, processing additive concentration and annealing temperatures are summarized in Table S1-S3. EQE plots were measured to explore the spectral response of HFQx-T:BZIC (1:1.5, w/w) and the typical EQE curves with different conditions are shown in Figure 2b. The EQE curves of these devices cover a broad response of 300-900 nm. Under optimal condition, the maximum EQE value achieves 50% at 740 nm for the device, meanwhile, according to the results of the EQE spectra, the calculated Jsc integrated from the EQE curve was 12.33 mA cm-2, in good agreement with that measuring from the J–V curves, the mismatch is only 2.7%.


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3 0 -3

(b) HFQx-T:BZIC as-cast Annealing Annealing+0.25% CN

60 50

EQE (%)

(a) -2 Current Density(mA cm )

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

-6

40 30

-9

20

-12

10

-15 -0.2

0.0

0.2

0.4

0.6

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0.8

0

1.0

Voltage(V)

HFQx-T:BZIC ac-cast Annealing Annealing+0.25% CN

300

400

500

600

700

800

900

Wavelength (nm)

Figure 2. (a) Typical J-V characteristics of the devices based on HFQx-T:BZIC (1:1.5, w/w) blends with different conditions under the illumination of AM 1.5G, 100 mW/cm2. (b) Corresponding EQE curves from the above devices. Table 2 Summary of the photovoltaic characteristics of the HFQx-T:BZIC blend films with different conditions at simulated 100 mW cm-2 AM 1.5G illumination. (the average values for 10 devices in the brackets) HFQx-T:BZIC

Annealing

Voc

Jsc

FF

PCE

(w/w)

(oC)

(V)

(mA/cm2)

(%)

(%)

1.5:1

None

0.86

7.67

31

2.0 [1.8]

120

0.84

9.73

34

2.8 [2.6]

None

0.85

8.92

33

2.5 [2.2]

120

0.85

11.58

40

3.9 [3.8]

None

0.85

11.37

41

4.0 [3.8]

120

0.85

12.55

49

5.2 [5.0]

120a

0.84

12.67

59

6.3 [6.1]

1:1

1:1.5

a

Under 0.25% CN with TA at 120 oC for 10 min.


10

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Hole Mobility To futherly understand TA effects and CN treatment on the device performance, the charge transport properties of the HFQx-T/BZIC blends were explored using the space charge limited current (SCLC) method with the hole only device (ITO/PEDOT:PSS/active layer/Au) and electron only device (ITO/ZnO/active layer/Al).62 The J1/2-V plots of HFQx-T/BZIC blend are demonstrated in Figure 3 and the corresponding hole/electron mobilities (µh/µe) data are listed in Table 3. The µh/µe of the HFQx-T/BZIC film are calculated to be 5.41×10−5 cm2 V−1 s−1/6.39×10−5 cm2 V−1 s−1 for the as-cast film and 9.85×10−5 cm2 V−1 s−1/8.97×10−5 cm2 V−1 s−1 for the annealed film. The investigations show TA can increase charge carrier mobilities, which are beneficial for improving photovoltaic parameters. After CN and TA treatment, both the hole and electron mobilities of the blend films increase, the µh and µe values of the active layer reach 1.15×10−4 cm2 V−1 s−1 and 1.11×10−4 cm2 V−1 s−1, respectively, which is much higher than that of as-cast films. It should be noted that, the HFQx-T:BZIC-based device exhibited a Voc of 0.84 eV, which is an impressive value for PSC with Egopt = 1.45 eV, indicating the energy loss (Eloss= Egopt – eVoc) in this work was 0.61 eV. However, the Jsc and FF are relatively low. As a trade-off, when Eloss is close to 0.60 eV, the quantum efficiency for charge generation often drops dramatically.63-64 Referring to the other literatures, the dependence of Jsc on light intensity and the exciton dissociation probabilities (Pdiss) were measured to gain some insights on the exciton dissociation process and charge collection efficiency in the active layer.65 Under different light intensities, we measured current to identify the charge recombination under the short circuit condition. In general, the relationship between Jsc and P can be described by the formula of Jsc∝Pα, whereas P means light intensity and the power-law component (α) implies the extent of charge recombination.66 As presented in Figure 3c, the α values were


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calculated as 0.915, 0.931, and 0.937 in the devices with as-cast, TA, and TA and 0.25% CN treatment conditions, respectively. This suggests that less charge recombination occurred in the device with TA and 0.25% CN, supporting its higher FF. The curves of photogenerated current density (Jph) versus effective voltage (Veff) of HFQx-T:BZIC-based devices are plotted in Figure 3d.67 Under short-circuit conditions, the Pdiss (Jph/Jsat, where Jsat stands for saturation photocurrent density) in the 120 oC annealed device is higher (83%) than 78% of the as-cast device. Moreover, a Pdiss of 88% was got using the optimal HFQx-T:BZIC based devices. The increased Pdiss values indicate that the TA and CN-treated device exhibits higher exciton dissociation and more efficient charge collection efficiency compared to those of the as-cast

30 25

(b)

HFQx-T:BZIC hole mobility as-cast Annealing Annealing + 0.25 % CN

30

20 15 10

20 15 10

5 0

HFQx-T:BZIC electron mobility as-cast Annealing Annealing + 0.25 % CN

25

1/2 1/2 -1 J (mA cm )

(a) 1/2 1/2 -1 J (mA cm )

device.

5

2

3

4 V (V)

5

0

6

2

3

4

5

6

V (V)

(d)

(c)

HFQx:BZIC as-cast (α=0.915) 10 Annealing (α=0.931) Annealing+0.25% CN (α=0.937)

1

10

Jph(mA cm-2)

-2 Jsc (mA cm )

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

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0

10

1

HFQx-T:BZIC as-cast (0.78) Annealing (0.83) Annealing+0.25% CN (0.88)

-1

10

-2

1

10

-2 Light intensity (mW cm )

100

10

-1

10

0

10

Veff (V)


12

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Figure 3. J1/2-V plots of HFQx-T:BZIC (1:1.5, w/w) in as-cast and optimized films for (a) hole mobilities, and (b) electron mobilities measured by SCLC method; (c) photocurrent versus light intensity of the as-cast and optimized devices based on HFQx-T:BZIC (1:1.5, w/w) blend. (d) photocurrent versus effective voltage of the as-cast and optimized devices based on HFQxT:BZIC (1:1.5, w/w) blend.

Table 3. The mobility data of HFQx-T:BZIC (1:1.5, w/w) blend films. Hole Mobility

Electron Mobility

(µh)

(µe)

(cm2 V−1 s−1)

(cm2 V−1 s−1)

HFQx-T:BZICa

5.41× 10-5

6.39× 10-5

0.84

HFQx-T:BZICb

9.85 × 10-5

8.97 × 10-5

1.09

HFQx-T:BZICc

1.15× 10-4

1.11× 10-4

1.04

Active layer

a

µh/µe

As-cast film. bWith TA at 120 oC for 10 min. cUnder 0.25% CN with TA at 120 oC for 10 min.

Morphological Characterization The morphology of BHJ solar cells is important for photovoltaic properties.68-69 Suitable domains and associated intimate mixing are desirable for excition separation and transport. To evaluate the effects of microstructure of active layers on device performance, the morphologies of HFQx-T:BZIC (1:1.5, w/w) blend films were investigated by the atomic force microscopy (AFM) in the tapping mode. As shown in Figure 4a, the surface of as-cast film shows a rootmean-square (RMS) roughness of 2.79 nm with slightly large aggregations and phase separations of HFQx-T and BZIC. After TA at 120 oC for 10 min (Figure 4b), the blend film exhibited


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smooth and more defined nanoscale morphology with lower RMS roughness of 1.89 nm. When treating the blend films with TA and 0.25 vol % CN treatment, the RMS roughness of the blend surface is slightly decreased to 1.77 nm (Figure 4c) corresponding with the highest PCE of 6.10%. The transmission electron microscopy (TEM) can be also used for exploring the nanoscale morphologies of HFQx-T:BZIC films under the same conditions. As shown in Figure 4d-f, the as-cast thin film of HFQx-T:BZIC (1:1.5, w/w) shows the obvious black aggregations compared to those of TA films (Figure 4e) and optimized films (Figure 4f), which would be negative for the charge carrier transport. The obvious distinction observed in the TEM images of the as-cast, annealing and optimized blend films can match well with the corresponding AFM images. The morphology of the HFQx-T:BZIC blend film with 0.25% CN and TA treatment shows a bicontinuous D/A interpenetrating network morphology, in qualitative agreement with the corresponding smallest RMS from the AFM images. From TEM images, we also find that HFQx-T:BZIC blend film with 0.25% CN and TA treatment shows much more homogeneous and a nano-phase segregated crystalline structure compared to the blend film as cast, which leads to higher photovoltaic performance.


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Figure 4. AFM height images (5 µm × 5 µm) of the active layers (insets are phase images of 5 µm × 5 µm size). (a) HFQx-T:BZIC; (b) HFQx-T:BZIC with TA; (c) HFQx-T:BZIC with TA and 0.25% CN treatment. TEM images of the active layers (d) HFQx-T:BZIC; (e) HFQxT:BZIC with TA; (f) HFQx-T:BZIC with TA and 0.25% CN treatment.

CONCLUSIONS In summary, based on a popular electron acceptor unit, benzotriazole, we have designed and synthesized a non-fullerene acceptor using D-π-A-π-D type ladder multifused benzotrizole central core. A simple design strategy by covalently fastening adjacent thiophene and benzotriazole has led to strong absorption in Vis-NIR region. Under CN and TA treatment, a homogeneous and nano-phase segregated crystalline structure could be observed, contributing to the formation of a favorable interpenetrating network with suitable phase separation in the active layer. By using a medium bandgap polymer HFQx-T as electron donor, PSCs based on HFQxT:BZIC (1:1.5, w/w) exhibits a moderate PCE of 6.30% with a Voc of 0.84 V, Jsc of 12.67 mA/cm2 and FF of 0.59. The results demonstrate that using a multifused benzotriazole structure as the central core is an efficient strategy to construct new and high performance non-fullerene acceptors. By this strategy, further follow-ups on organic small molecules with a D-π-A-π-D core as building block for electron acceptor materials in OPVs are in progress in our laboratory.


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ASSOCIATED CONTENT Supporting Information The Supporting information (SI) available:: Experimental details including synthesis, related figures and tables.

AUTHOR INFORMATION Corresponding Author * E-mail: [email protected]

ACKNOWLEDGEMENTS This work has been financially supported by the National Natural Science Foundation of China (51673205), National Key Research & Development Projects of China (2017YFA0206600) , Hunan Provincial Natural Science Foundation for Distinguished Young Scholars (2017JJ1029), Project of Innovation-driven Plan in Central South University, China (2016CX035) and the Fundamental Research Funds for the Central Universities of Central South University (2016zzts023)

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Table of Contents

3

HFQx-T BZIC

Current density (mA cm-2)

1.0

Blend

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

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0.8 0.6 0.4 0.2 0.0 300

400

500

600

700

800

900

0 -3

HFQx-T:BZIC as-cast Annealing Annealing+0.25 % CN

-6 -9 -12 -15 -0.2

0.0

0.2

Wavelength (nm)

0.4

0.6

0.8

1.0

Voltage (V)


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Thieno[3,2-b]pyrrolo-Fused Pentacyclic ... - ACS Publications

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