optically transparent semiconducting polymer nanonetwork for … · 2016. 11. 21. · optically...
TRANSCRIPT
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Optically transparent semiconducting polymer
nanonetwork for flexible and transparent electronics
Kilho Yua,b,c,1, Byoungwook Parka,b,c,1, Geunjin Kimb,c, Chang-Hyun Kima,c,
Sungjun Parka, Jehan Kimd, Suhyun Junga,b,c, Soyeong Jeonga,b,c, Sooncheol
Kwonb,c, Hongkyu Kangb,c, Junghwan Kimb,c, Myung-Han Yoona, Kwanghee
Leea,b,c,2
aDepartment of Nanobio Materials and Electronics, School of Materials Science and Engineering,
Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea; bHeeger Center
for Advanced Materials, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of
Korea; cResearch Institute for Solar and Sustainable Energies, Gwangju Institute of Science and
Technology, Gwangju 61005, Republic of Korea; dPohang Accelerator Laboratory, Pohang University
of Science and Technology, Pohang 37673, Republic of Korea
1These authors contributed equally to this work.
2E-mail: [email protected]
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I. Supplementary Methods
PLED solutions for emissive layers. PDY-132 (Super Yellow, Merck) and MEH-PPV (Mr
425,000, Sigma-Aldrich) were dissolved in chlorobenzene at concentrations of 7 mg ml1 and
8 mg ml1, respectively. SPW-111 (Merck) and F8BT (Mr 35,000, American Dye Source)
were separately dissolved in toluene at a concentration of 9 mg ml1.
Large-area FT-FET device fabrication. A solution of polydimethylsiloxane (PDMS,
Sylgard 184 silicone elastomer, Dow Corning) mixed with a hardener (10:1 weight ratio) was
spin cast onto a cleaned glass slide (10 cm 10 cm) at 5000 rpm for 20 s, and the film was
subsequently annealed at 70 ºC for 1 h. A PEN (t 125 m) substrate was then adhered to the
PDMS surface for the subsequent fabrication processes. The PEN substrate was cleaned via
sequential ultrasonication in water, acetone, and isopropyl alcohol and treated with UV/ozone
exposure for 3 min. For the bottom electrodes, PEDOT:PSS (CleviosTM P Jet 700, Heraeus)
was directly patterned via an inkjet-printing method using a Dimatix Materials Printer (DMP-
2800 Series, Fujifilm USA). A DPP2T/PS (15/85 wt % ratio) solution was spin cast onto the
substrate in an inert nitrogen atmosphere, and the film was annealed at room temperature for
3 minutes under low-vacuum conditions (102 Torr). To fabricate the gate insulating layer,
we used poly(methyl methacrylate) (PMMA, Mr 120,000, Sigma-Aldrich). Note that we
could not use CYTOP for the insulator because the subsequent inkjet patterning of the
PEDOT:PSS for the gate electrode onto CYTOP would be impossible because of the very
low surface energy of CYTOP. The PMMA (80 mg ml1) dissolved in n-butyl acetate was
spin cast onto the semiconducting layer to a thickness of 500 nm, and the film was annealed
at 80 ºC for 1 h. The measured capacitance of the PMMA was 6.0 nF cm2. Finally, the top-
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gate electrode was also fabricated through inkjet printing the PEDOT:PSS. No annealing
process was used for the bottom and top PEDOT:PSS contacts. The resulting device could be
easily detached from the supporting substrate because of the PDMS.
FT-FET-LED integrated device fabrication. PDMS supports on glass substrates (10 cm
10 cm) were prepared as described for large-area FT-FET device fabrication. We attached a
PEN/indium-tin-oxide (ITO) substrate to the PDMS surface for the subsequent fabrication
processes. The PEN/ITO substrate was cleaned via sequential ultrasonication in water,
acetone, and isopropyl alcohol and treated with UV/ozone exposure for 20 min. Then, a zinc
oxide (ZnO) precursor solution (2.5 wt % zinc acetate dehydrate and 0.7 wt % ethanolamine
in 2-propanol) was spin cast at 4000 rpm onto the ITO surface, and the film was then
annealed at 130 ºC for 10 min. Subsequently, a polyethyleneimine (PEI) solution (0.05 wt %
in 2-propanol) was spin cast at 5000 rpm onto the ZnO surface. The various light-emitting
layers were spin coated from solution, and the films were subsequently thermally annealed at
70 ºC for 10 min under an inert nitrogen atmosphere. Then, 20-nm-thick MoOx was thermally
deposited, and PEDOT:PSS (CleviosTM P AI4083, Heraeus) with 1 wt % fluorosurfactant
(Capstone FS-31, DuPont) was spin coated at 1000 rpm and subsequently thermally annealed
at 100 ºC for 10 min to improve hole injection and for FET fabrication there on. Thin Au (15
nm) semi-transparent source/drain electrodes were thermally deposited and patterned using
shadow masks. Finally, charge-transport layers, gate insulators, and gate electrodes were
fabricated identically to those of the TGBC FETs.
FET characterization. The I-V characteristics of the FETs were measured using a Keithley
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4200 source meter. The saturation was calculated from the equation
μsat = (𝜕√𝐼DS
𝜕𝑉GS)
2
(2𝐿/𝑊𝐶i),
and the linear was calculated as
μlin = 𝜕𝐼DS
𝜕𝑉GS ∙
1
𝑉DS (𝐿/𝑊𝐶i),
where IDS is the drain-source current, VGS is the gate voltage, VDS is the drain-source voltage,
Ci is the capacitance per unit area, and L and W are the channel length and width, respectively.
The FETs were also characterized at various temperatures in a cryostat.
PLED characterization. The I-V-L characteristics of the FT-FET-PLEDs were measured
using a PR650 spectrophotometer with two Keithley 2400 source meters.
TEM characterization. The samples were obtained by peeling the spin-cast films on glass
substrates and transferring them onto 200-mesh copper grids (Electron Microscopy Sciences,
USA). The TEM images were acquired using a Tecnai G2 F30 S-Twin microscope (FEI USA)
operated at an acceleration voltage of 300 kV.
X-ray characterization. 2D GIWAXS images were acquired at the 3C-SAXSl beam line at
the Pohang Accelerator Laboratory (PAL) using a monochromatic X-ray radiation source of
10.22 keV ( 1.213 Å ) and a 2D X-ray detector (Mar165 CCD). The samples were placed
on a z-axis goniometer and were maintained under vacuum conditions (10-3 Torr) during
irradiation.
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AFM characterization. The AFM instrument (XE-100, Park Systems) was operated in
tapping mode for samples on glass substrates. To remove PS, we thoroughly rinsed the
DPP2T/PS film with propylene glycol monomethyl ether acetate (PGMEA, Sigma-Aldrich)
and dried it for several minutes under a nitrogen flow and low-vacuum conditions (102 Torr)
before testing.
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II. Supplementary Notes
Note S1. Structural analysis of DPP2T and DPP2T/PS based on optical absorption
spectra. Optical absorption spectra can provide crucial information about chain aggregation
(Fig. 1B). The absorption spectrum of the DPP2T solution, which shows spectral features
characteristic of a polymer chain (1), is identical to that of the DPP2T/PS solution; thus, the
conformation of DPP2T is not affected by the PS in the solution phase. Meanwhile, the
DPP2T film presents a broadened absorption spectrum and an increased intensity ratio of the
0-1 transition (0-1 754 nm) over the 0-0 transition (0-0 832 nm), indicating dominant
intermolecular stacking in the solid phase (2). By contrast, the spectral features of the
DPP2T/PS film are similar to those of the solution phase, with only a slightly increased 0-1
transition, indicating that the interchain order is considerably suppressed compared with that
of the pure DPP2T film.
Note S2. FET characteristics of the pure DPP2T films. DPP2T devices without PS but
with DPP2T contents equal to those of the DPP2T/PS devices were also investigated to
exclude the dependence on the DPP2T concentration and isolate the effect of PS blending at
each blending condition (Fig. S11). The pure DPP2T devices show a moderate monotonically
increase and saturation of as the concentration increases (because even the 100% DPP2T
layer is very thin [t 10 nm], thinner films may exhibit morphological discontinuity and
defects) (3).
Note S3. Measurements and modeling of T-dependent device characteristics. We referred
to the theoretical framework utilized by Sirringhaus and colleagues (4, 5), which accounts for
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the T- and gate voltage (VGS)-dependent drain-source current (IDS), and we modeled our data
accordingly to describe the charge-transport mechanisms of the two systems (Fig. S16A). The
transport theories dictate the saturation-regime IDS as a power-law function of VGS VT
(where VT is the threshold voltage), with its characteristic exponent being converted into the
energetic width of the density of states (DOS) (6-9) for localized states. In turn, IDS obeys a
power law defined by the exponent , as follows: IDS VGS VT. The log-log representation
of the data in Fig. S16B shows good linearity over a wide T range, enabling the unambiguous
extraction of and reliable reproducibility of the measured device performances. In Fig.
S16C, surprisingly low values approaching 2 with very low T dependence indicate that both
systems are exceptionally resilient to pervasive disorder, which is consistent with the results
obtained for other high- near-amorphous copolymer materials (5). Most importantly, the
slope of versus 1/T reflects the degree of thermal accessibility of the localized sites, and the
lower dependence observed in DPP2T/PS indicates a considerably reduced energetic disorder
compared with that in pure DPP2T (see Fig. S17).
Note S4. Structural analysis of DPP2T/PS. According to the TEM images of DPP2T and
DPP2T/PS films, the flexible PS matrix seems to prevent the entanglement of the rigid
DPP2T chains by providing a more flexible surrounding environment. An additional
structural analysis using atomic force microscopy (AFM) was performed, revealing a large
difference in the nano-morphology of the polymer chains between DPP2T and DPP2T/PS
films. To directly investigate the morphology of the DPP2T nanonetwork in DPP2T/PS, we
first thoroughly rinsed the film with propylene glycol monomethyl ether acetate (PGMEA),
which effectively dissolves PS but not DPP2T. Figure S19 presents 2D AFM images of the
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PS-removed DPP2T/PS film. In the PS-removed DPP2T/PS film, we could observe a
nanonetwork structure of DPP2T, which exhibited an extensively connected fibrillar structure
with significantly reduced chain entanglement compared with a film of pure DPP2T (Fig.
S18A) that was cast from a diluted DPP2T solution (15%) for a direct comparison of the
morphological differences at the same DPP2T concentration, with and without PS. The
critical role of PS in determining the structural characteristics of DPP2T is clearly evident.
Additionally, these findings support our conclusion that the DPP2T forms a network structure
at the bottom of a DPP2T/PS film, which remains even after the film has been thoroughly
rinsed with PGMEA.
Note S5. Effective of the DPP2T/PS films. Given the smaller effective channel area in the
DPP2T/PS films, the effective (eff) normalized to the effective channel coverage is
expected to be higher than the normally measured device ; thus, eff will be a more relevant,
intrinsic value, and its correlation with the charge-pathway structure created in the PS matrix
will be more useful. The resultant eff values of the DPP2T/PS devices as a function of the
effective channel coverage are shown in Fig. S20. The effective channel area was extracted
via image thresholding of the TEM images (Fig. S21). Note that although this image analysis
may not provide the exact value of the effective channel area, it enables us to qualitatively
investigate the approximate channel coverage of the DPP2T/PS. The channel coverage and
the corresponding eff were estimated in a range of DPP2T contents from 15% to 100%,
where percolation is sufficient for reliable analysis. We find that eff exponentially decreases
as the channel coverage broadens. However, GIWAXS analysis of the blend films reveals that
the interchain stacking order gradually increases as the channel coverage increases (Fig. S22).
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Therefore, the formation of a fibrillar network structure and its nanoscopic morphological
features might be crucial factors that greatly improve the transport property despite the
reduced interchain stacking order (see Figs. S23 and S24). Consequently, the eff of
DPP2T/PS with the lowest interchain stacking order can be as high as 27 cm2 V1 s1, and
the transport property approaches its intrinsic limit in a semiconducting polymer, despite the
decreasing interchain stacking order. Note that the value of 27 cm2 V1 s1 that was
obtained based on the approximate channel coverage extracted from the TEM images may
not represent the exact of the DPP2T network in DPP2T/PS (15/85 wt %). However, this
analysis clearly indicates that the intrinsic charge-transport properties of the DPP2T
nanonetwork in DPP2T/PS can be significantly improved compared with those of neat
DPP2T domains.
Note S6. Correlation between intermolecular structure and charge transport in
DPP2T/PS. Although, no long-range interchain stacking order is observed, partial -
ordering may exist at small length scales in DPP2T/PS. This short-range intermolecular
aggregation is sufficient to promote efficient intramolecular charge transport along the
polymer backbone (10, 11). Clearly, the interchain crystalline order is much higher in pure
DPP2T than in DPP2T/PS. However, the structural and energetic disorder induced by chain
entanglement and phase boundaries should also be much more prevalent in a pure DPP2T
film, hindering charge transport. Furthermore, intramolecular charge delocalization is
expected to be significantly hindered in the entangled DPP2T chains and fibrils of such a film.
As a result, efficient intrachain charge transport should be suppressed; charges should be
forced to undergo much more interchain hopping through localized states. These hypotheses
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are consistent with our transport analyses. Extended, closely packed interchain - coupling
should promote more efficient transport along both interchain and intrachain paths (12).
However, our results demonstrate that reducing interchain interactions may improve the
charge transport in solution-processable polymeric semiconductors and that reducing the
interchain-aggregation-related structural disorder may be more important than altering the
interchain ordering.
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III. Supplementary Figures
Fig. S1. Optical characteristics of PS. Transmittance spectrum of a PS thin film (40 nm).
The inset shows the absorption spectrum of the PS film, indicating an optical band gap of 4
eV.
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Fig. S2. Optical characteristics of DPP2T and P3HT. Normalized absorption spectra of
DPP2T and P3HT films. Inset shows the chemical structure of P3HT.
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Fig. S3. Optical spectroscopy of DPP2T and DPP2T/PS. Tr spectra of DPP2T/PS blend films
at various concentration ratios. The inset shows the Ta values of DPP2T/PS blend films at
various DPP2T concentrations. The curved line indicates the trend in Ta with the variation in
the DPP2T concentration.
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Fig. S4. Structural analysis of DPP2T/PS. The elemental mapping of S (shown in green) in
the DPP2T/PS film was obtained via energy-dispersive X-ray spectroscopy line-scan analysis.
The scale bar represents 300 nm.
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Fig. S5. Structural analysis of PS. Normalized 2D GIWAXS image of a PS film. The wide
arc-pattern around q 1.32 Å1 indicates that the PS is amorphous.
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Fig. S6. Structural analysis based on GIWAXS measurements. (A,B) Normalized 1D profiles
of DPP2T, DPP2T/PS, and PS films along the (A) out-of-plane and (B) in-plane directions.
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Fig. S7. Cross-sectional diagram of a TGBC FET. The Au and Al serve as the bottom
source/drain and top gate electrodes, respectively. Pure DPP2T or DPP2T/PS acts as the
charge-transport layer. For the gate insulating layer, CYTOP (t 550 nm) is used. The
measured capacitance of the CYTOP layer is 3.5 nF cm2.The channel length and width are
40 µm and 1000 µm, respectively.
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Fig. S8. Output characteristics of TGBC FETs at room temperature. (A) DPP2T. (B)
DPP2T/PS. VGS varies from 0 V to 60 V. Both devices show clear FET characteristics with a
low zero-VDS current, good IDS linearity in the linear regime, and the modulation of IDS with
VGS.
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Fig. S9. Representative linear regime transfer characteristics of pure DPP2T and DPP2T/PS
FETs under a VDS of 5 V.
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Fig. S10. Saturation distribution for DPP2T/PS (15/85 wt % ratio) FETs.
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Fig. S11. Hole values of DPP2T FETs at various DPP2T concentrations. The curved line
indicates the trend in the hole value as the DPP2T concentration is varied. The vertical lines
(whiskers) indicate the 10th-to-90th percentile ranges. The minimum and maximum values
are indicated by asterisks.
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Fig. S12. T-dependent transfer characteristics of DPP2T FETs in the linear regime under
various VDS. (A) 2 V. (B) 4 V. (C) 6 V. (D) 8 V. T was varied from 100 K to 310 K.
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Fig. S13. T-dependent transfer characteristics of DPP2T/PS FETs in the linear regime under
various VDS. (A) 2 V. (B) 4 V. (C) 6 V. (D) 8 V. T was varied from 100 K to 310 K.
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Fig. S14. Schematic diagram of the local energy difference between aggregated and
amorphous DPP2T regions.
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Fig. S15. Schematic illustration of the dominant charge-transport direction in pure DPP2T
and DPP2T/PS films.
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Fig. S16. Measurements and modeling of T-dependent device characteristics. (A) Rendering
of the measured transfer curves by means of the power-law current-voltage model on a semi-
logarithmic scale. The measured characteristics (symbols) for each T were fitted to the
power-law relationship (solid lines). The channel length and width are 40 m and 1 mm,
respectively, and VDS is fixed at 60 V. (B) Log-log plot of the IDS as a function of the
effective gate overdrive voltage. VT is 0 V for a DPP2T FET and 8 V for a DPP2T/PS FET.
(C) Extracted exponents as a function of 1/T for DPP2T and DPP2T/PS.
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Fig. S17. T-dependent transfer characteristics of DPP2T and DPP2T/PS devices. (A,B)
Normalized IDS1/2-VGS curves of (A) DPP2T and (B) DPP2T/PS. These curves present the
VGS dependence of IDS1/2 at varying temperatures, showing T-dependent behaviors that can
be correlated with localized energy states. The lower T dependence of the DPP2T/PS curve
indicates that DPP2T/PS exhibits reduced disorder compared with DPP2T. VDS is fixed at 60
V.
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Fig. S18. Structural analysis of pure DPP2T and DPP2T/PS. 2D top-surface images of diluted
pure DPP2T (15%) and DPP2T/PS films measured using atomic force microscopy (AFM).
(A,B) Topographic images of (A) pure DPP2T and (B) DPP2T/PS. (C,D) Phase images of (C)
pure DPP2T and (D) DPP2T/PS. The scale bars represent 500 nm. (E,F) Corresponding
surface 1D profiles for (E) pure DPP2T and (F) DPP2T/PS. Notably, the pure DPP2T film
was deposited from a dilute DPP2T solution (15%) with the same DPP2T concentration as
that of the DPP2T/PS solution but without PS. Despite dilution, pure DPP2T forms entangled
fibrillar structures and, inevitably, abundant phase boundaries (phase image). We could not
determine the exact DPP2T/PS structure from the AFM images, but a separated phase
structure is evident in the phase image of the DPP2T/PS; the structure appears to show a
DPP2T nanonetwork partially embedded in an amorphous PS matrix.
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Fig. S19. 2D AFM images of PS-removed DPP2T/PS. (A) Topographic image. (B) Phase
image. The scale bars represent 500 nm. (C) Corresponding 1D surface profile. Notably, the
nanonetwork structure of DPP2T can be clearly observed in the PS-removed DPP2T/PS film.
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Fig. S20. Effective-channel-area-normalized eff versus channel-coverage percentile plot for
PS-blend FETs. The effective channel area was extracted from various TEM images via
image thresholding.
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Fig. S21. Estimation of the effective channel areas of DPP2T/PS films at various
concentration ratios. (A–F) Transformed TEM images obtained via an image thresholding
method for DPP2T/PS films with concentration ratios (wt % ratios) of (A) 15/85, (B) 30/70,
(C) 50/50, (D) 70/30, (E) 80/20, and (F) 90/10. (G) Estimated channel area as a function of
DPP2T content.
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Fig. S22. Structural analysis of DPP2T/PS. Normalized 2D GIWAXS patterns of DPP2T/PS
films at various concentration ratios (wt % ratios): (A) 30/70, (B) 50/50, (C) 70/30, and (D)
100/0.
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Fig. S23. T-dependent characteristics of DPP2T/PS devices. (AD) T-dependent transfer
characteristics of DPP2T/PS FETs in the linear regime at various concentration ratios of (A)
, (B) (C) , and (D) under a VDS of 2 V. T was varied from 100 K to
310 K.
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Fig. S24. T-dependent characteristics of DPP2T/PS devices. (A) Arrhenius plots of the T-
dependent linear values for DPP2T/PS FETs at various concentration ratios under a VDS of
2 V. (B) EA as a function of the DPP2T content in the high-T ( 190 K) and low-T ( 190 K)
regimes for DPP2T/PS FETs.
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Fig. S25. Inkjet-printed PEDOT:PSS source/drain electrodes on a PEN substrate. The contact
and channel regions are clearly defined by the inkjet-printing method. The estimated channel
length is 100 µm. The scale bar represents 200 µm.
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Fig. S26. Large-area FT-FET device. A photograph of our all-solution-processed, all-polymer
FT-FET device (10 cm 10 cm) containing an array of 1650 FETs. Because of its high
transparency (Ta 86%) and colorless nature, we can see through the device without color
distortion. It is even difficult to locate the individual FT-FETs with the naked eye.
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Fig. S27. Output characteristics of FT-FETs. VGS is modulated from 0 V to 60 V. The
lateral-F dependence and waviness of the curves are attributable to the low conductivity (
700 S/cm) of the polymeric metal (PEDOT:PSS) electrodes, in which quasi-free charge
carriers are subject to substantial energetic disorder and trap-sites upon charge injection and
transport, resulting in a F-dependent charge flow (i.e., conductivity) in PEDOT:PSS
electrodes.
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Fig. S28. Transfer characteristics of FT-FETs before and after 1000 bending cycles at a
bending radius of R 5 mm. We detect no performance degradation in the transfer
characteristics even after 1000 bending cycles.
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Fig. S29. Schematic diagrams of FT-FET-PLED devices. (A) Cross-sectional device structure.
(B) Energy band diagram for each layer.
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Fig. S30. Optical transmittance spectra of FT-FET-PLED devices. (A) Tr spectra of normal
yellow PLED and integrated yellow FT-FET-PLED devices. (B) Tr spectra of the layers
through which the emitted light passes in the normal yellow PLED and integrated yellow FT-
FET-PLED devices.
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Fig. S31. Optical characteristics of the light emitted from FT-FET-PLED devices. (A) CIE
(1931) x-y color coordinates of the light emitted from normal PLED and integrated FT-FET-
PLED devices. (B–D) EL spectra of normal PLED and integrated FT-FET-PLED devices
fabricated with (B) SPW-111, (C) MEH-PPV, and (D) F8BT.
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Fig. S32. Chemical structures of the semiconducting polymers used for the emissive layers.
(A) PDY-132, (B) MEH-PPV, and (C) F8BT. The chemical structure of SPW-111 is not
known.
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IV. Supplementary Tables
Table S1. Mobility values of DPP2T and DPP2T/PS FETs with various concentration ratios.
DPP2T DPP2T/PS
DPP2T
contents (%)
a ()
(cm2 V
-1 s
-1)
max
(cm2 V
-1 s
-1)
min
(cm2 V
-1 s
-1)
a ()
(cm2 V
-1 s
-1)
max
(cm2 V
-1 s
-1)
min
(cm2 V
-1 s
-1)
1 - - - 0.0800
(0.0537) 0.163 0.0124
2 0.0787
(0.0630) 0.237 0.00693
0.153
(0.151) 0.399 0.00183
3 0.199
(0.120) 0.421 0.00762
0.516
(0.275) 1.079 0.217
5 0.323
(0.101) 0.499 0.139
0.888
(0.228) 1.29 0.601
8 0.490
(0.111) 0.747 0.355
0.964
(0.286) 1.48 0.598
10 0.440
(0.0952) 0.601 0.277
1.13
(0.277) 1.78 0.738
15 0.435
(0.0611) 0.518 0.321
1.56
(0.524) 3.07 0.872
20 0.523
(0.110) 0.785 0.418
1.16
(0.257) 1.60 0.715
25 0.591
(0.0951) 0.773 0.438
1.17841
(0.141) 1.41 1.01
30 0.594
(0.0937) 0.814 0.481
1.08359
(0.228) 1.47 0.618
50 0.660
(0.0897) 0.792 0.535
1.06
(0.219) 1.49 0.778
70 0.678
(0.105) 0.821 0.531
1.06
(0.175) 1.46 0.828
80 0.618
(0.0729) 0.748 0.484
0.853
(0.0824) 0.983 0.726
90 0.634
(0.102) 0.800 0.483
0.841
(0.0775) 0.977 0.701
100 0.679
(0.0809) 0.801 0.548 - - -
a is the average mobility. is the standard deviation.
max and
min are the maximum and the minimum
mobilities, respectively.
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Table S2. Transmittance values of FT-FET devices with different layering conditions.
Condition Ta (%) Tmax (%) Tmin (%) T550 (%)
1 85.9 89.1 76.0 87.5
2 85.5 88.3 76.2 87.8
3 85.7 87.8 76.2 87.6
4 87.7 90.7 78.5 88.9
All-layer 85.8 89.1 77.2 88.1
Ta is the average transmittance. Tmax and Tmin are the maximum and the minimum transmittances, respectively.
T550 is the transmittance at 550 nm. These values were estimated in the visible range (from 400 nm to 700
nm).
Condition 1 denotes a PEN substrate. Condition 2 denotes condition 1 + PEDOT:PSS (S/D) layer. Condition 3
denotes condition 2 + DPP2T/PS. Condition 4 denotes condition 3 + PMMA layer. All-layer denotes condition
4 + PEDOT:PSS (G) layer. These layering conditions are identical to the device-fabrication conditions.
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