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Efficient Blue, Green, and Red Electroluminescence from CarbazoleFunctionalized Poly(spirobifluorene)s Keyan Bai,†,‡ Shumeng Wang,† Lei Zhao,† Junqiao Ding,*,† and Lixiang Wang*,† †

State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China ‡ University of Chinese Academy of Sciences, Beijing 100049, P. R. China S Supporting Information *

ABSTRACT: Based on a carbazole-functionalized polyspirobifluorene with high fluorescence quantum yield and deep-blue emission, a series of blue-, green-, and red-emitting polymers have been successfully developed by independently incorporating dibenzothiophene-S,S-dioxide (3,7SO), 4,7-diphenylbenzothiadiazole (DPBT), and 4,7-dithienylbenzothiadiazole (DTBT) as the copolymerized units to tune the emission color in the whole visible region. The effect of their loadings on the electrochemical, photophysical, and electroluminescent properties is investigated in detail. It is found that PCzSF-3,7SO15, PCzSF-DPBT15, and PCzSF-DTBT03 show the best blue, green, and red device performance, revealing state-of-the-art luminous efficiencies of 5.6, 21.6, and 4.4 cd A−1 along with CIE coordinates of (0.16, 0.16), (0.32, 0.60), and (0.61, 0.34), respectively. The results clearly indicate that the carbazole-functionalized polyspirobifluorene is a promising platform to construct high-efficiency multicolor polymers suitable for PLEDs.

1. INTRODUCTION Conjugated polymers have been widely applied for polymer light-emitting diodes (PLEDs) because of their excellent costeffective solution processability.1−11 To fulfill the application in full-color flat-panel displays, the development of appropriate red-, green-, and blue-emitting (RGB) polymers seems to be indispensable.12−14 Polyfluorene (PF) is one of the most attractive blue-emitting polymers with high photoluminescence quantum yields (PLQYs) and wide bandgaps.15−21 Moreover, its emission can be facilely tailored in the range of the whole visible region through the introduction of narrow-bandgap chromophores into the polymeric main chain or side chain.22−29 For instance, Yang et al. designed high-performance RGB PFs, showing maximum luminous efficiencies of 6.1, 17.6, and 7.0 cd A−1 accompanied by Commission Internationale de L’Eclairage (CIE) coordinates of (0.62, 0.36), (0.37, 0.56), and (0.15, 0.17), respectively.26 As an analogue, polyspirobifluorene (PSF) is believed to be superior to PF since the unwanted blue spectral instability originating from the fluorenone defects or aggregates could be avoided due to the characteristic spiro structure.30−35 Early in © 2017 American Chemical Society

2003, PSF-based RGB polymers were reported to give luminous efficiencies of 1.0, 7.0, and 2.9 cd A−1 as well as CIE coordinates of (0.67, 0.33), (0.31, 0.58), and (0.16, 0.19), respectively.30 Compared with RGB PFs, the unsatisfactory device performance is reasonably attributed to the existed alkyloxy as the solubilizing group in RGB PSFs.34 The electrondonating nature of alkyloxy may endow the polymer with mixed charge transfer (CT) character, resulting in low PLQYs and bathochromic emission. To solve this problem, very recently, we have developed a highly emissive carbazole-functionalized homopolymer poly[2′,7′-bis(3,6-dioctylcarbazo-9-yl)spirobifluorene] (PCzSF) by fully replacing the peripheral four octyloxy groups with 3,6-dioctylcarbazole.35 Unlike the alkyloxy-decorated counterpart poly[2′,3′,6′,7′-tetrakis(octyloxy)spirobifluorene] (PROSF: λem = 455 nm and ΦPL = 0.20), the CT effect from pendant to backbone is found to be completely eliminated in PCzSF, which exhibits a blue-shifted Received: June 30, 2017 Revised: August 15, 2017 Published: August 29, 2017 6945

DOI: 10.1021/acs.macromol.7b01393 Macromolecules 2017, 50, 6945−6953

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Macromolecules

Scheme 1. Synthetic Route (a) and Molecular Structures (b) of Blue-, Green-, and Red-Emitting PSFs Together with the Reference PCzSF

Figure 1. 1H NMR spectra of the blue-emitting PSFs compared with PCzSF and the monomer 2Br3,7SO.

2. RESULTS AND DISCUSSION Synthesis and Characterization. The synthetic procedure is outlined in Scheme 1. Different Ar units including 3,7SO, DPBT, and DTBT were copolymerized into PCzSF to afford blue-emitting polymers PCzSF-3,7SO05, PCzSF-3,7SO15, and PCzSF-3,7SO30 and green-emitting polymers PCzSF-DPBT05, PCzSF-DPBT15, and PCzSF-DPBT30, together with redemitting polymers PCzSF-DTBT01, PCzSF-DTBT03, and PCzSF-DTBT05. The actual Ar content in these polymers can be calculated quantitively from their 1H NMR spectra. Taking the blue-emitting PSFs as an example (Figure 1), the three proton signals located at 7.61, 7.75, and 7.92 ppm in the monomer 3,7-dibromodibenzothiophene-S,S-dioxide (2Br3,7SO) are found to be shifted to 7.16, 7.58, and 8.06 ppm in the polymers, respectively, in accordance with the literature,36 and their relative intensity is gradually enhanced as

emission of 422 nm and an improved PLQY of 0.60 in solid states. Consequently, a deep-blue electroluminescence (EL) is achieved with an external quantum efficiency of 3.0% and CIE coordinates of (0.17, 0.06). Encouraged by the preliminary results, here we further demonstrate the color tuning in PCzSF. That is by incorporating an additional dibenzothiophene-S,S-dioxide (3,7SO), 4,7-diphenylbenzothiadiazole (DPBT), or 4,7dithienylbenzothiadiazole (DTBT) unit into the backbone of PCzSF, a series of PSF-based RGB polymers have been designed and synthesized via Suzuki polycondensation (Scheme 1). Among them, PCzSF-3,7SO15, PCzSF-DPBT15, and PCzSF-DTBT03 have the best blue, green, and red device performance, revealing state-of-the-art luminous efficiencies as high as 5.6, 21.6, and 4.4 cd A−1 along with CIE coordinates of (0.16, 0.16), (0.32, 0.60), and (0.61, 0.34), respectively. 6946


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Macromolecules the feed ratio is rising. By comparing the integral of these peaks with that of the 6.77 ppm signal related to PCzSF, the 3,7SO loading is determined to be very close to the feed ratio (Table 1). This implies that 3,7SO has been successfully introduced into the main chain of PCzSF during polymerization. Table 1. Structure Characteristics of Blue-, Green-, and RedEmitting PSFs Ar content in the polymers (mol %) classification

polymer

feed ratio

actual contenta

Mnb (kDa)

PDIb

Tdc (°C)

blue

PCzSF-3,7SO05 PCzSF-3,7SO15 PCzSF-3,7SO30 PCzSF-DPBT05 PCzSF-DPBT15 PCzSF-DPBT30 PCzSF-DTBT01 PCzSF-DTBT03 PCzSF-DTBT05

5 15 30 5 15 30 1 3 5

5.6 15.1 30.2 5.5 14.7 29.0 1.3 3.2 5.5

111 103 56 86 82 92 100 113 81

2.7 2.8 2.4 2.2 2.3 3.1 2.0 2.1 2.2

393 414 414 375 379 405 392 406 410

green

red

Figure 2. CV curves of the blue-emitting PSFs compared with PCzSF.

acceptor 3,7SO moieties is responsible for the tendency in dilute solutions,37−39 consistent with the corresponding emission that displays a bathochromic shift from 415 nm of PCzSF to 425 nm of PCzSF-3,7SO30. More obvious variation is observed in solid films owing to the contribution from both intra- and intermolecular CT (Figure 3b). For example, PCzSF has a PL spectrum with well-defined vibronic structures involving 0−0, 0−1, and 0−2 peaks. By contrast, the PL spectra of the blue-emitting PSFs containing 3,7SO turn out to be broad and featureless, and the maximum emission is significantly red-shifted by 35−45 nm relative to PCzSF. Despite this, they all give bright blue lights in the range 457− 467 nm with high PLQYs of 0.40−0.48 (Table 2), indicative of their potential as blue emitters for PLEDs. As for the green-emitting PSFs based on DPBT, an additional absorption occurs at about 430 nm, and the related intensity is dependent on the DPBT content (Figure 3c).40,41 Accordingly, PCzSF-DPBT05 exhibits a dual fluorescence in toluene solution, where the blue emission at 414 nm and green emission at 510 nm are from the PCzSF backbone and DPBT unit, respectively. Attributable to the efficient energy transfer from PCzSF to DPBT, the blue emission is weakened considerably, and the green emission becomes dominant for PCzSF-DPBT15 and PCzSF-DPBT30. On going from solutions to films, the intermolecular energy transfer also plays an important role on the PL spectra so that the blue emission is completely quenched even for PCzSF-DPBT05 with a 5% low content of DPBT (Figure 3d). When further raising the DPBT content to 30%, the emissive peak shifts from 513 nm to a longer wavelength of 528 nm for PCzSF-DPBT30, while the corresponding PLQY is close to that of PCzSFDPBT05. Similarly, a new weak band located at 520 nm is found in the UV−vis spectra of the DTBT-containing red-emitting PSFs (Figure 3e). Such an absorption corresponding to DTBT does not match well with the PL of PCzSF,42,43 leading to poor spectral overlap and thus inefficient energy transfer from PCzSF to DTBT. Reasonably, the blue emission dominates the whole solution PL spectra along with a small fraction of red emission from DTBT. Even in films, there still exists a blue emission residue for PCzSF-DTBT01, PCzSF-DTBT03 and PCzSF-DTBT05 (Figure 3f). The difference implies that the energy transfer from PCzSF to DTBT in the red-emitting PSFs is not as effective as that from PCzSF to DPBT in the green-

a Calculated from the 1H NMR spectra. bDetermined by GPC in the THF using polystyrene as the standard. cDecomposition temperatures corresponding to a 5% weight loss determined by TGA in N2.

Gel permeation chromatography (GPC) was used to measure the number-average molecular weight (Mn) and polydispersity index (PDI). Although they have high Mn of 56−113 kDa along with PDI of 2.0−3.1, all of these RGB PSFs are readily soluble in common organic solvents to ensure the generation of high quality films via solution processing. Meanwhile, their decomposition temperatures corresponding to a 5% weight loss exceed 370 °C, and no glass transition or melting behaviors are detected in the range 25−300 °C (Figure S4). The observed good thermal stability is expected to be beneficial for the realization of the long-term PLEDs. Electrochemical Properties. The electrochemical properties of the RGB PSFs were explored by cyclic voltammetry (CV). The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels were estimated with ferrocene/ferrocenium (Fc/Fc+) as the standard (4.8 eV below vacuum). For the blue-emitting PSFs, as shown in Figure 2, the oxidation does not depend on the 3,7SO content, and their HOMO levels are similar to that of the homopolymer PCzSF (−5.74 eV). Nevertheless, with the increasing 3,7SO content, the reduction moves toward a more positive potential, and the corresponding LUMO level is decreased from −2.32 eV of PCzSF-3,7SO05 to −2.84 eV of PCzSF-3,7SO30. So the incorporated 3,7SO moiety may facilitate the electron injection and transporting. In analogy to the blue-emitting ones, the same trend is also observed for the green- and red-emitting PSFs (Figure S5). Photophysical Properties. Figure 3a−d depicts the UV− vis absorption and photoluminescence (PL) spectra for these three classes of RGB PSFs. Similar to PCzSF, the blue-emitting PSFs possess two distinct absorption bands peaked at 359 and 389 nm (Figure 3a). With the increasing content of 3,7SO, the former from the carbazole-based side chain remains nearly unchanged, whereas the latter from the main chain is redshifted accompanied by a slightly elevated intensity. The intramolecular CT between the donor spirobifluorene and 6947


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Figure 3. UV−vis absorption and PL spectra in toluene solutions (left) together with PL spectra in solid films (right) for the blue- (a, b), green- (c, d), and red-emitting PSFs (e, f). All the PL spectra are detected under an excitation wavelength of 356 nm, and the film thickness is about 40 nm for solid-state samples.

emitting ones. Meanwhile, with the increasing DTBT content from PCzSF-DTBT01 to PCzSF-DTBT05, the maximum emission is up from 614 to 646 nm, and the PLQY is down from 0.69 to 0.52. EL Properties. To investigate the EL properties of the RGB PSFs, their PLEDs with a configuration of ITO/PEDOT:PSS/ polymer/SPPO13/LiF/Al were fabricated (Figure 4a). Herein PEDOT:PSS represents poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and serves as the hole injection layer, while SPPO13 represents 9,9′-spirobi(fluorene)-2,7-diylbis(diphenylphosphine oxide) and acts as the electron-transporting layer. The detailed PLEDs’ characteristics are summarized in Table 3. As can be clearly seen, the blue-emitting polymer PCzSF-3,7SO15, green-emitting polymer PCzSF-DPBT15, and red-emitting polymer PCzSF-

DTBT03 achieve the best device performance among all these RGB PSFs. The EL spectra peak at 460, 528, and 625 nm for PCzSF-3,7SO15, PCzSF-DPBT15, and PCzSF-DTBT03 (Figure 4b), respectively, corresponding to CIE coordinates of (0.16, 0.16), (0.32, 0.60), and (0.61, 0.34). Furthermore, we note that the EL spectrum of PCzSF-DTBT03 still exhibits a blue light residue and is almost the same as its PL counterpart. The observation suggests that under electric excitation the charge trapping seems to be negligible in PCzSF-DTBT03, which is quite different from the situation in red-emitting PFs.44,45 Except for PCzSF-DTBT03, the EL spectra of PCzSF3,7SO15 and PCzSF-DPBT15 are almost independent of the driving voltages, indicative of the good spectral stability (Figure S6). 6948


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Table 2. Photophysical and Electrochemical Properties for Blue-, Green-, and Red-Emitting PSFs Compared with PCzSF classification

polymer

reference blue

PCzSF PCzSF-3,7SO05 PCzSF-3,7SO15 PCzSF-3,7SO30 PCzSF-DPBT05 PCzSF-DPBT15 PCzSF-DPBT30 PCzSF-DTBT01 PCzSF-DTBT03 PCzSF-DTBT05

green

red

λabsa (nm) 359, 359, 359, 359, 357, 358, 361, 359, 359, 359,

389 389 390 391 389 389, 389, 387 387, 387,

423 426 520 520

λPLa (nm) 415 419 423 425 414, 413, 512 412, 413, 413,

510 510 610 610 613

λPLb (nm)

ΦPLc

HOMO/LUMOd (eV)

422 457 465 467 513 518 528 420, 614 420, 624 420, 646

0.60 0.48 0.49 0.40 0.85 0.90 0.89 0.69 0.73 0.52

−5.74/−2.32 −5.74/−2.32 −5.74/−2.41 −5.74/−2.84 −5.74/−2.35 −5.74/−2.35 −5.74/−2.94 −5.74/−2.36 −5.74/−2.38 −5.74/−2.38

a Measured in toluene solutions of 10−5 M at 298 K. bMeasured in films at 298 K. cSolid state fluorescence quantum yields measured by integrating sphere and excited at 356 nm. dHOMO = −e(Eox + 4.8 V) and LUMO = −e(Ered + 4.8 V), where Eox and Ered are the onset values of the first oxidation and reduction waves, respectively.

Figure 4. Selected best device performance for blue-, green-, and red-emitting PSFs: (a) device configuration; (b) EL spectra at 6 V; (c) current density−voltage−luminance characteristics; (d) luminance efficiency and EQE as a function of luminance. Inset: CIE chromaticity diagram.

with a turn-on voltage of 4.2 V, a maximum brightness of 3250 cd m−2, and a peak luminous efficiency of 4.4 cd A−1. The obtained efficiencies are among the highest ever reported for RGB PSFs (Table S1) and comparable to those of RGB PFs.

As discussed above, the introduced 3,7SO can reduce the LUMO levels to favor the electron injection and transporting while not affecting the HOMO levels for blue-emitting PSFs. With regard to the homopolymer PCzSF (3.6 V, 1750 cd m−2), therefore the 3,7SO-containing polymer PCzSF-3,7SO15 realizes a reduced turn-on voltage of 3.2 V and an increased brightness of 6820 cd m−2 (Figure 4c). Correspondingly, the maximum luminous efficiency is improved from 1.7 cd A−1 of PCzSF to 5.6 cd A−1 of PCzSF-3,7SO15 (Figure 4d). In addition, after the introduction of DPBT and DTBT, PCzSFDPBT15 emits a green EL with a turn-on voltage of 3.4 V, a maximum brightness of 27 400 cd m−2, and a peak luminous efficiency of 21.6 cd A−1, and PCzSF-DTBT03 emits a red EL

3. CONCLUSIONS In summary, a series of RGB PSFs have been developed by incoporating 3,7SO, DPBT, and DTBT into the backbone of a carbazole-functionalized homopolymer PCzSF that possesses deep-blue emission and high PLQY. Because of the intra- and intermolecular CT or energy transfer, the color tuning toward blue, green, and red emissions is successfully realized in these developed polymers. Their corresponding PLEDs show the 6949


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Macromolecules Table 3. Device Performance for Blue-, Green-, and Red-Emitting PSFs classification

polymer

Vona (V)

Lmax (cd m−2)

ηl,max (cd A−1)

ηl,max (lm W−1)

ηext,max (%)

blue

PCzSF-3,7SO05 PCzSF-3,7SO15 PCzSF-3,7SO30 PCzSF-DPBT05 PCzSF-DPBT15 PCzSF-DPBT30 PCzSF-DTBT01 PCzSF-DTBT03 PCzSF-DTBT05

3.8 3.2 3.4 4.0 3.4 3.2 4.0 4.2 4.0

3620 6820 5600 17000 27400 37000 5040 3250 2250

3.1 5.6 4.1 19.0 21.6 18.3 5.3 4.4 1.9

2.3 4.8 3.4 12.8 17.5 14.1 3.8 3.5 1.6

2.8 3.8 2.5 5.6 6.0 5.0 4.4 4.2 2.6

green

red

CIEb (x, y) 0.16, 0.16, 0.16, 0.30, 0.32, 0.35, 0.44, 0.61, 0.63,

0.11 0.16 0.19 0.57 0.60 0.60 0.25 0.34 0.33

Turn-on voltage at a brightness of 1 cd m−2. bCIE coordinates at 6 V are listed for comparison with the s-RGB standard (R = 0.64, 0.33; G = 0.30, 0.60; B = 0.15, 0.06). Lmax: maximum brightness; ηl, max: maximum luminous efficiency; ηp, max: maximum power efficiency; ηext, max: maximum EQE. a

maximum luminous efficiencies of 5.6, 21.6, and 4.4 cd A−1 with CIE coordinates of (0.16, 0.16), (0.32, 0.60), and (0.61, 0.34), respectively. This work, we believe that represents an important progress on PSF-based RGB polymers and will shed light on their further applications in full-color displays.

PCzSF-3,7SO30. 2BrCzSF (125.3 mg, 0.100 mmol), 2BCzSF (353.9 mg, 0.250 mmol), and 2Br3,7SO (56.1 mg, 0.150 mmol) were used. 1H NMR (400 MHz, CDCl3), δ (ppm): 8.06 (d, J = 6.5 Hz, 0.7 H), 7.93 (d, J = 7.7 Hz, 1.3 H), 7.80 (s, 1.6 H), 7.73 (d, J = 14.8 Hz, 5.3 H), 7.58 (s, 0.9 H), 7.50 (s, 1.3 H), 7.33 (s, 0.9 H), 7.13 (s, 1.4 H), 7.09−6.99 (m, 3.7 H), 6.99−6.87 (m, 4.8 H), 6.77 (d, J = 6.7 Hz, 2.0 H), 2.91−2.32 (m, 8.0 H), 1.52 (s, 9.1 H), 1.22 (s, 45.6 H), 0.84 (s, 15.1 H). 13C NMR (101 MHz, CDCl3), δ (ppm): 150.84, 148.63, 141.38, 139.01, 137.84, 134.55, 132.66, 128.01, 125.93, 123.36, 122.29, 120.81, 119.20, 109.11, 65.75, 35.93, 32.26, 31.91, 29.54, 29.44, 29.29, 22.68, 14.12. Anal. Calcd for [(C81H92N2)70(C12H6O2S)30]n: C 87.17; H 8.17; N 2.36; S 1.16. Found: C 87.15; H 8.59; N 2.18; S 0.84. PCzSF-DPBT05. 2BrCzSF (282.0 mg, 0.225 mmol), 2BCzSF (353.9 mg, 0.250 mmol), and 2BrDPBT (11.1 mg, 0.025 mmol) were used. 1H NMR (400 MHz, CDCl3), δ (ppm): 8.12 (s, 0.1 H), 7.94 (s, 1.9 H), 7.81 (s, 0.3 H), 7.72 (s, 4.8 H), 7.57 (s, 0.2 H), 7.48 (s, 1.8 H), 7.35 (s, 1.3 H), 7.18 (s, 0.2 H), 6.98 (s, 3.3 H), 6.92 (s, 5.1 H), 6.77 (s, 3.8 H), 2.57 (s, 8.0 H), 1.53 (s, 8.9 H), 1.24 (s, 44.6 H), 0.85 (s, 13.5 H). 13C NMR (101 MHz, CDCl3), δ (ppm): 150.73, 148.60, 141.66, 138.95, 137.60, 134.25, 127.86, 125.94, 123.35, 122.15, 120.68, 119.60, 109.12, 65.94, 35.93, 32.24, 31.92, 29.55, 29.32, 22.68, 13.93. Anal. Calcd for [(C81H92N2)95(C18H10N2S)5]n: C 88.60; H 8.60; N 2.66; S 0.15. Found: C 88.68; H 8.60; N 2.60; S 0.18. PCzSF-DPBT15. 2BrCzSF (219.3 mg, 0.175 mmol), 2BCzSF (353.9 mg, 0.250 mmol), and 2BrDPBT (33.5 mg, 0.075 mmol) were used. 1H NMR (400 MHz, CDCl3), δ (ppm): 8.11 (s, 0.3 H), 8.06− 7.85 (m, 2.6 H), 7.80 (s, 0.8 H), 7.73 (d, J = 20.0 Hz, 5.4 H), 7.55 (s, 0.9 H), 7.49 (d, J = 9.8 Hz, 1.4 H), 7.32 (s, 1.2 H), 7.16 (s, 0.5 H), 7.09−6.96 (m, 4.1 H), 6.91 (s, 4.4 H), 6.76 (s, 2.9 H), 2.56 (s, 8.0 H), 1.53 (d, J = 12.5 Hz, 9.4 H), 1.21 (s, 42.5 H), 0.83 (s, 12.9 H). 13C NMR (101 MHz, CDCl3), δ (ppm): 150.73, 148.60, 141.66, 138.95, 137.60, 134.25, 129.68, 127.86, 125.94, 123.35, 122.15, 120.68, 119.60, 109.12, 65.94, 35.93, 32.24, 31.92, 29.55, 29.44, 29.32, 22.68, 13.93. Anal. Calcd for [(C81H92N2)85(C18H10N2S)15]n: C 88.17; H 8.47; N 2.88; S 0.49. Found: C 88.02; H 8.36; N 2.80; S 0.51. PCzSF-DPBT30. 2BrCzSF (125.3 mg, 0.100 mmol), 2BCzSF (353.9 mg, 0.250 mmol), and 2BrDPBT (66.9 mg, 0.150 mmol) were used. 1H NMR (400 MHz, CDCl3), δ (ppm): 8.11 (d, J = 16.7 Hz, 0.7 H), 7.97 (s, 2.4 H), 7.83 (s, 1.4 H), 7.76 (d, J = 15.7 Hz, 4.9 H), 7.59 (d, J = 5.7 Hz, 1.1 H), 7.51 (d, J = 4.7 Hz, 1.3 H), 7.36 (s, 1.4 H), 7.19 (d, J = 7.7 Hz, 1.0 H), 7.14−6.99 (m, 4.9 H), 6.94 (s, 4.0 H), 6.80 (d, J = 8.9 Hz, 2.4 H), 2.83−2.31 (m, 8.0 H), 1.58 (s, 10.6 H), 1.24 (s, 49.3 H), 0.86 (s, 15.1 H). 13C NMR (101 MHz, CDCl3), δ (ppm): 151.09, 148.82, 141.18, 139.16, 137.60, 134.55, 129.92, 127.93, 126.54, 123.41, 122.51, 121.40, 119.53, 109.69, 65.93, 36.13, 32.45, 32.09, 29.73, 29.64, 29.48, 22.87, 14.30. Anal. Calcd for [(C81H92N2)70(C18H10N2S)30]n: C 87.39; H 8.21 N 3.28; S 1.13. Found: C 86.23; H 8.15; N 3.18; S 1.10. PCzSF-DTBT01. 2BrCzSF (307.1 mg, 0.245 mmol), 2BCzSF (353.9 mg, 0.250 mmol), and 2BrDTBT (2.1 mg, 0.005 mmol) were used. 1H NMR (400 MHz, CDCl3), δ (ppm): 7.98 (s, 0.3 H), 7.93 (d, J = 7.1 Hz, 1.8 H), 7.77 (s, 0.9 H), 7.71 (s, 4.5 H), 7.55 (d, J = 7.3 Hz, 0.1 H), 7.47 (d, J = 3.3 Hz, 1.7 H), 7.33 (s, 1.5 H), 7.08 (s, 0.3 H),

4. EXPERIMENTAL SECTION Materials. All chemicals were purchased from the Beijing Chemical Plant, Aldrich, or Alfa and used without further purification unless otherwise stated. Toluene was freshly distilled before usage. 2,7Dibromo-2′,7′-bis(3,6-dioctylcarbazo-9-yl)-9,9′-spirofluorene (2BrCzSF),35 2,7-bis(5-phenyl-1,3,2-dioxaborinan-2-yl)-2′,7′-bis(3,6dioctylcarbazo-9-yl)-9,9′-spiroifluorene (2BCzSF),35 2Br3,7SO,46 4,7bis(4-bromophenyl)-2,1,3-benzothiadiazole (2BrDPBT),41 and 4,7bis(5-bromothiophen-2-yl)benzo-2,1,3-thiadiazole (2BrDTBT)47 were prepared according to the literature. General Procedure of Suzuki Polycondensation. Taking PCzSF-3,7SO05 as an example, the procedure is as follows: Under carefully degassing with argon, a mixture of 2BrCzSF (282.0 mg, 0.225 mmol), 2BCzSF (353.9 mg, 0.250 mmol), 2Br3,7SO (9.4 mg, 0.025 mmol), Pd2(dba)3 (0.9 mg), Aliquat 336 (20.0 mg), and SPhos (3.2 mg) was dissolved in toluene and heated to 80 °C. Then, aqueous 2 M K2CO3 was added. After vigorous stirring for 1.5 h in 96 °C, benzene boronic acid (15.0 mg) in toluene (4 mL) was added. The mixture was reacted for 5 h, followed by addition of 1 mL of bromobenzene for another 5 h. Finally, the sodium diethyldithiocarbamate trihydrate (1.0 g) dissolved in deionized water (15 mL) was added into the mixture under argon for 24 h. After cooling, the mixture was diluted with dichloromethane and washed with deionized water. The organic phase was dried over anhydrous Na2SO4, filtered, concentrated, and poured into methanol to get the polymer. The final purification was carried out by Soxhlet extraction with acetone for about 24 h and then precipitated in methanol. 1H NMR (400 MHz, CDCl3), δ (ppm): 8.06 (s, 0.3 H), 7.93 (s, 1.4 H), 7.72 (s, 4.5 H), 7.48 (s, 1.5 H), 7.34 (s, 1.1 H), 7.13 (s, 0.3 H), 6.98 (s, 2.8 H), 6.91 (s, 4.8 H), 6.77 (s, 3.8 H), 2.57 (s, 8.0 H), 1.52 (s, 9.2 H), 1.23 (s, 44.9 H), 0.85 (s, 13.5 H). 13C NMR (101 MHz, CDCl3), δ (ppm): 150.36, 148.85, 141.47, 140.15, 138.95, 137.79, 134.25, 127.74, 126.26, 123.35, 120.39, 119.06, 109.33, 66.04, 35.92, 32.23, 31.92, 29.55, 29.43, 29.32, 22.68, 14.11. Anal. Calcd for [(C81H92N2)95(C12H6O2S)5]n: C 88.67; H 8.53; N 2.53; S 0.15. Found: C 88.50; H 8.59; N 2.43; S 0.35. PCzSF-3,7SO15. 2BrCzSF (219.3 mg, 0.175 mmol), 2BCzSF (353.9 mg, 0.250 mmol), and 2Br3,7SO (28.1 mg, 0.075 mmol) were used. 1H NMR (400 MHz, CDCl3), δ (ppm): 8.08 (s, 0.5 H), 7.95 (s, 1.3 H), 7.82 (s, 0.5 H), 7.74 (s, 4.7 H), 7.61 (s, 0.5 H), 7.50 (s, 1.4 H), 7.36 (s, 0.9 H), 7.16 (s, 0.8 H), 7.00 (s, 3.2 H), 6.93 (s, 4.9 H), 6.79 (s, 3.0 H), 2.59 (s, 8.0 H), 1.54 (s, 8.7 H), 1.25 (s, 44.3 H), 0.87 (s, 13.3 H). 13C NMR (101 MHz, CDCl3), δ (ppm): 150.42, 148.76, 141.61, 140.41, 138.95, 137.56, 134.13, 128.01, 126.16, 123.37, 122.33, 120.60, 119.31, 108.96, 66.10, 35.93, 32.24, 31.92, 29.55, 29.44, 29.29, 22.68, 14.12. Anal. Calcd for [(C81H92N2)85(C12H6O2S)15]n: C 88.13; H 8.40; N 2.47; S 0.50. Found: C 87.94; H 8.55; N 2.38; S 0.56. 6950


Article

Macromolecules 6.98 (d, J = 2.9 Hz, 2.2 H), 6.94−6.82 (m, 5.5 H), 6.77 (s, 4.5 H), 2.56 (s, 8.0 H), 1.51 (s, 9.4 H), 1.22 (s, 46.0 H), 0.84 (t, J = 6.4 Hz, 13.8 H). 13C NMR (101 MHz, CDCl3), δ (ppm): 150.46, 148.93, 141.96, 140.49, 140.38, 139.37, 138.95, 137.09, 134.12, 127.47, 126.35, 123.35, 122.28, 120.95, 120.39, 119.12, 108.83, 65.96, 35.92, 32.23, 31.91, 29.55, 29.43, 29.32, 22.68, 14.11. Anal. Calcd for [(C81H92N2)99(C14H6N2S3)1]n: C 88.70; H 8.65; N 2.58; S 0.09. Found: C 88.77; H 8.58; N 2.38; S 0.10. PCzSF-DTBT03. 2BrCzSF (294.6 mg, 0.235 mmol), 2BCzSF (353.9 mg, 0.250 mmol), and 2BrDTBT (6.3 mg, 0.015 mmol) were used. 1H NMR (400 MHz, CDCl3), δ (ppm): 8.05 (d, J = 16.2 Hz, 0.4 H), 7.95 (s, 1.6 H), 7.86 (s, 0.6 H), 7.74 (d, J = 9.5 Hz, 4.6 H), 7.59 (d, J = 9.9 Hz, 0.1 H), 7.50 (s, 1.9 H), 7.37 (s, 1.5 H), 7.12 (s, 0.3 H), 6.99 (s, 2.8 H), 6.93 (s, 5.0 H), 6.78 (s, 3.4 H), 2.58 (s, 8.0 H), 1.54 (s, 8.6 H), 1.25 (s, 42.9 H), 0.89−0.85 (t, J = 6.4 Hz 12.8H). 13C NMR (101 MHz, CDCl3), δ (ppm): 150.56, 148.75, 141.52, 140.30, 139.59, 139.05, 137.61, 134.25, 127.82, 126.34, 123.35, 122.44, 121.17, 120.20, 119.35, 109.12, 66.05, 35.93, 32.24, 31.92, 29.55, 29.43, 29.32, 22.68, 14.12. Anal. Calcd for [(C81H92N2)97(C14H6N2S3)3]n: C 88.51; H 8.61; N 2.61; S 0.27. Found: C 88.48; H 8.64; N 2.48; S 0.26. PCzSF-DTBT05. 2BrCzSF (282.0 mg, 0.225 mmol), 2BCzSF (353.9 mg, 0.250 mmol), and 2BrDTBT (10.6 mg, 0.025 mmol) were used. 1H NMR (400 MHz, CDCl3), δ (ppm): 8.03 (d, J = 9.8 Hz, 0.2 H), 7.95 (d, J = 7.7 Hz, 1.6 H), 7.78 (s, 0.8 H), 7.73 (s, 4.3 H), 7.57 (d, J = 9.0 Hz, 0.2 H), 7.49 (d, J = 5.9 Hz, 1.7 H), 7.36 (s, 1.6 H), 7.11 (s, 0.2 H), 7.00 (s, 2.5 H), 6.98−6.85 (m, 5.4 H), 6.77 (d, J = 7.1 Hz, 3.8 H), 2.58 (s, 8.0 H), 1.53 (s, 9.0 H), 1.24 (s, 44.4 H), 0.86 (t, J = 6.7 Hz, 13.3 H). 13C NMR (101 MHz, CDCl3), δ (ppm): 150.99, 148.94, 141.59, 140.07, 139.51, 138.78, 137.58, 134.25, 127.77, 126.36, 123.36, 122.32, 121.23, 120.28, 119.37, 109.13, 66.47, 35.93, 32.24, 31.92, 29.55, 29.44, 29.33, 22.68, 14.12. Anal. Calcd for [(C81H92N2)95(C14H6N2S3)5]n: C 88.32; H 8.58; N 2.65; S 0.46. Found: C 88.33; H 8.61; N 2.56; S 0.39. Measurements and Characterization. 1H and 13C NMR spectra were recorded with a Bruker Avance 400 NMR spectrometer. Using the polystyrene as a standard, gel permeation chromatography (GPC) measurements were performed to determine molecular weight in tetrahydrofuran with a Waters 410 instrument. Elemental analysis was performed using a Bio-Rad elemental analysis system. UV−vis and PL spectra were measured with a PerkinElmer Lambda 35 UV−vis spectrometer and a PerkinElmer LS 50B spectrofluorometer, respectively. The film PLQYs were measured using an integrating sphere on a quantum yield measurement system (C10027, Hamamatsu Photonics). Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed under a flow of nitrogen with PerkinElmer-TGA 7 and PerkinElmer-DSC 7 system, respectively. Cyclic voltammetry (CV) of the polymer films coated on the working electrode was conducted on a CHI660a electrochemical analyzer with Bu4NClO4 as the electrolyte. Acetonitrile and N,Ndimethylformamide were used as the solvents for the anodic and cathodic scanning, respectively. Device Fabrication and Testing. The ITO glass substrates with a sheet resistance of 15 ohm/square were cleaned with acetone, detergent, and distilled water and baked at 120 °C for 2 h. After treating with violet-ozone (UVO) for 0.5 h, a dispersion of PEDOT:PSS (Batron-P4083, Bayer AG) in water was spin-coated onto ITO substrates and baked at 120 °C for another 40 min. Subsequently, the RGB PSFs at a concentration of 6 mg mL−1 in toluene were spin-coated on PEDOT:PSS as the emitting layer (EML) and annealed at 80 °C for 0.5 h inside a nitrogen-filled glovebox. On top of the EML, a 50 nm thickness of SPPO13 was thermally deposited at a pressure of 4.0 × 10−4 Pa as the hole-blocking and electron-transporting layer. Finally, 1 nm of LiF followed by 100 nm of Al was deposited in sequence as the cathode. The active area of the device was 14 mm2. The EL spectra and CIE coordinates were measured using a CS2000 spectra colorimeter. The current−voltage and luminance−voltage curves were measured using a Keithley 2400/ 2000 source meter calibrated by a silicon photodiode. All the measurements were carried out at room temperature under ambient

conditions. The EQE was calculated from the luminance, current density, and EL spectrum assuming a Lambertian distribution.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.macromol.7b01393. 1 H NMR spectra , 13C NMR spectra, and CV curves of the green- and red-emitting PSFs compared with PCzSF; TGA and DSC curves and device performance of the polymers; device performance comparison among PSFbased multicolor polymers (PDF)

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (J.D.). *E-mail: [email protected] (L.W.). ORCID

Junqiao Ding: 0000-0001-7719-6599 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors acknowledge the financial support from the 973 Project (2015CB655001) and the National Natural Science Foundation of China (Nos. 51573183, 91333205, 21474106, and 51322308).

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REFERENCES

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