Donor-acceptor copolymer based on dioctylporphyrin: Synthesis and application in organic field-effect transistors

Article abstract of DOI:10.1016/j.polymer.2012.03.015

A novel alternating D-A copolymer, PPor-BT, with dioctylporphyrin (Por) as a donor unit and 5,6-bis(octyloxy)benzo-2,1,3-thiadiazole (BT) as an acceptor unit, was designed and synthesized by Pd-catalyzed Sonogashira-coupling reaction. The copolymer showed good solubility and film-forming ability. PPor-BT exhibited a broad absorption band from 350 to 950 nm with two peaks centered at 456 and 818 nm corresponding to the Soret band and Q-bands absorption of porphyrin segments, respectively. The employment of electron deficient BT unit to construct donor-acceptor structure observably broadened the absorption spectrum and enhanced the Q-band absorption of the porphyrin-based polymer. The HOMO and LUMO energy levels of the polymer are -5.06 eV and -3.63 eV, respectively. The solution-processed organic field-effect transistors (OFETs) were fabricated with bottom gate/top-contact geometry. The mobility of PPor-BT based OFEFs reached 4.3 × 10^-5 cm² V^-1 s^-1 with an on/off current ratio of 10⁴. This mobility is among the highest values for porphyrin-based polymers.

Full text of DOI:10.1016/j.polymer.2012.03.015

Polymer 53 (2012) 1864e1869
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Polymer
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Donor-acceptor copolymer based on dioctylporphyrin: Synthesis and application
in organic field-effect transistors
,
a
,
b
,
a,
*
Xiaochen Wang a, Yugeng Wen b, Hao Luo b, Gui Yu b , Xiaoyu Li , Yunqi Liu , Haiqiao Wang
*
*
*
a State Key Laboratory of OrganiceInorganic Composites, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
b Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel alternating DeA copolymer, PPoreBT, with dioctylporphyrin (Por) as a donor unit and 5,6-
bis(octyloxy)benzo-2,1,3-thiadiazole (BT) as an acceptor unit, was designed and synthesized by Pd-
catalyzed Sonogashira-coupling reaction. The copolymer showed good solubility and film-forming
ability. PPoreBT exhibited a broad absorption band from 350 to 950 nm with two peaks centered at
456 and 818 nm corresponding to the Soret band and Q-bands absorption of porphyrin segments,
respectively. The employment of electron deficient BT unit to construct donor-acceptor structure
observably broadened the absorption spectrum and enhanced the Q-band absorption of the porphyrin-
based polymer. The HOMO and LUMO energy levels of the polymer are ꢀ5.06 eV and ꢀ3.63 eV,
respectively. The solution-processed organic field-effect transistors (OFETs) were fabricated with bottom
gate/top-contact geometry. The mobility of PPoreBT based OFEFs reached 4.3 ꢁ 10ꢀ5 cm2 Vꢀ1 sꢀ1 with
an on/off current ratio of 104. This mobility is among the highest values for porphyrin-based polymers.
Ó 2012 Elsevier Ltd. All rights reserved.
Received 16 December 2011
Received in revised form
28 February 2012
Accepted 7 March 2012
Available online 13 March 2012
Keywords:
Porphyrin
Doctor-acceptor copolymer
Organic field-effect transistors
1. Introduction
mobilities up to 0.32 cm2 Vꢀ1 sꢀ1 [11]. However, there have been
only a few reports about porphyrin-containing polymers used in
Porphyrin derivates have been intensively studied over the past
century because of their unique nature. The porphyrin is a hetero-
cyclic macrocycle derived from four pyrroline subunits inter-
OFETs as active layers [10,14]. Performances of porphyrin-based
polymer transistors are quite poor. For example,
porphyrinediacetylene polymer transistors only showed mobilities
connected via their a-carbon atoms via methine bridges [1]. The
of 10ꢀ7 cm2 Vꢀ1 sꢀ1 at room temperature [10].
macrocycle is a highly-conjugated system with deep color. The
name porphyrin comes from a Greek word for purple. In recent
years, porphyrin molecules and relative polymers have attracted
tremendous interest due to their potential applications in opto-
electronic devices, such as organic light emitting diodes [2e9],
organic field-effect transistors (OFETs) [10e14], and organic solar
cells [14e20].
The performances of organic semiconductors rely on the
inherent structural uniqueness, such as planarity, conjugation, and
their packing and intermolecular interactions. In this regard,
porphyrins would be one of the best candidates for organic tran-
sistors because of their multiple inter- and/or intramolecular
Recently, considerable attention has been focused on donor-
acceptor (DeA) conjugated copolymers, where electron-rich and
electron deficient units are polymerized in an alternating fashion
along the polymer backbone, because their electronic and opto-
electronic properties could be efficiently tuned by intramolecular
charge transfer (ICT) [22e31]. The hybridization of the highest
occupied molecular orbital (HOMO) on the donor moiety and the
lowest unoccupied molecular orbital (LUMO) on the acceptor
moiety provides a method to tune the electronic and optoelectronic
properties for various needs. High carrier mobilities were obtained
from the DeA copolymer systems through the manipulation of
intramolecular charge transfer, morphology, or gate dielectric
surface modification [27e29]. Among those well investigated
acceptors, 2,1,3-benzothiadiazole (BT) unit has previously been
interactions, such as
pep stacking, electrostatic interactions, as
well as metal-ligand coordination, in different derivates [21]. OFET
devices based on small porphyrin molecules exhibit carrier
proven to enhance
p-stacking morphologies, leading to high charge
carrier mobility [32].
Here we designed and synthesized a novel alternating DeA
copolymer, PPoreBT, with 5,15-dioctylporphyrin (Por) as donor
unit, and 5,6-bis(octyloxy)benzo-2,1,3-thiadiazole (BT) as acceptor
unit. The structure of PPoreBT is shown in Scheme 1. In this
* Corresponding authors. Tel.: þ86 010 64419631.
E-mail addresses: yug@iccas.ac.cn (G. Yu), lixy@mail.buct.edu.cn (X. Li), liuyq@
iccas.ac.cn (Y. Liu), wanghaiqiao@mail.buct.edu.cn (H. Wang).
0032-3861/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.polymer.2012.03.015

X. Wang et al. / Polymer 53 (2012) 1864e1869
1865
diffraction (XRD) measurements of thin films were performed in
reflection mode at 40 kV and 200 mA with Cu-Ka radiation using
a 2 kW Rigaku X-ray diffractometer. Atomic force microscopy (AFM)
images of the thin films were obtained on a Nanoscope IIIa AFM
(Digital Instruments) operating in tapping mode.
2.2. Fabrication of field-effect transistor
OFETs were fabricated on highly doped silicon substrates with
thermally grown 300-nm-thick silicon oxide (SiO2) insulating layer,
where the substrate served as a common gate electrode. Prior to
polymer semiconductor deposition, the substrates were treated
with the silylating agent octyltrichlorosilane (OTS). Thin semi-
conductor films were then deposited by spin-coating the polymer
solutions in chlorobenzene:THF (1:1) on the substrates. The film
thickness was measured by an XP-2 surface profilometer (Ambios
Technology). The samples were then dried and annealed at 140 ꢂC
under nitrogen. Source-drain gold electrodes were deposited on
the polymer layer by vacuum evaporation under 7 ꢁ 10ꢀ4 Pa to
form top-contact geometry. The electrical characterization of the
transistor devices was performed using a Keithley 4200 semi-
conductor parameter analyzer.
Scheme 1. Molecular structure of PPoreBT.
contribution, the 5,15-dioctylporphyrin unit was used to enhance
both the coplanarity of the molecular backbone and the
pep
3. Synthesis of the monomers
stacking in the solid state of the copolymer, while the electron
deficient BT unit was employed to construct donor-acceptor
structure, which would facilitate high-performance OFETs
[27e29]. In addition, the well-defined alternating DeA structure of
polymer combined with the linear alkyl side chains is expected to
optimize the molecular packing in the solid state. OFETs based on
the polymer were fabricated and characterized. The highest hole
mobility of PPoreBT reached 4.3 ꢁ 10ꢀ5 cm2 Vꢀ1 sꢀ1 with an ON/
OFF current ratio of 104.
3.1. Dipyrromethane (2)
Formaldehyde gas (generated by cracking paraformaldehyde
(35 g,1.16 mol) at 160 ꢂC) passed into an oxygen-free solution of TFA
(13.68 g, 0.12 mol) in pyrrole (2 L, 30 mol) under a slow flow of
nitrogen. After all the paraformaldehyde had been transferred, the
reaction mixture was stirred at room temperature for another
30 min. The resulting yellow solution was washed with 10% NaOH
solution before distilled to remove excess pyrrole. Then the crude
product was purified by column chromatography (petroleum ether:
EtOAc: Et3N 100: 10: 1) to afford the product as a white crystal
2. Experimental section
2.1. Measurements and characterization
(71 g, 42%). 1H NMR (600 MHz, CDCl3):
d 7.90 (br, 2H), 6.69 (s, 2H),
6.17 (d, 2H), 6.06 (s, 2H), 4.00 (s, 2H). ESIeMS: m/z ¼ 147.1 (Mþ þ 1).
The molecular weight of the polymer was measured by gel
permeation chromatography (GPC) method. The GPC measure-
ments were performed on Waters 515-2410 with polystyrenes as
reference standard and tetrahydrofuran (THF) as an eluent. All new
compounds were characterized by nuclear magnetic resonance
spectra (NMRs) and/or Mass spectra (MS). The NMRs were recorded
on a Bruker AV 600 spectrometer in CDCl3 or THF at room
temperature. Chemical shifts of 1H NMR were reported in ppm.
Splitting patterns were designated as s (singlet), d (doublet), t
(triplet), m (multiplet), and br (broaden). Mass spectra were
measured on a GCT-MS micromass (U.K.) spectrometer using the
electron impact (EI) mode or on a Bruker Daltonics BIFLEX III
MALDI-TOF Analyzer using MALDI mode. Elemental analyses were
performed on a Flash EA 1112 analyzer. UVeVis absorption spectra
were recorded on a Shimadzu spectrometer model UV-3150.
Absorption spectrum measurement of the polymer solution was
carried out in THF (analytical reagent) at 25 ꢂC. Absorption spec-
trum measurement of the polymer film was carried out on the
quartz plates with the polymer film spin-coated from the polymer
solution in THF (analytical reagent) at 25 ꢂC. The electrochemical
cyclic voltammetry was conducted on a Zahner IM6e electro-
chemical workstation with a Pt plate, Pt wire, and Ag/Agþ electrode
as the working electrode, counter electrode, and reference elec-
trode, respectively, in a 0.1 mol/L tetrabutylammonium hexa-
fluorophosphate (Bu4NPF6) acetonitrile solution. Polymer thin films
were formed by drop-casting polymer solutions in THF (analytical
reagent) on the working electrode and were then dried in air. X-Ray
3.2. 5,15-Dioctylporphyrin (3)
A solution of 1-decyne (0.684 g, 4.8 mmol) and dipyrromethane
(0.702 g, 4.8 mmol) in CH2Cl2 (1 L) was purged with nitrogen for
30 min, and then trifluoroacetic acid (TFA) (0.3 g, 2.6 mmol) was
added. The mixture was stirred for 3 h at room temperature, and
then DDQ (1.84 g, 8 mmol) was added. After the mixture was stirred
at room temperature for an additional 30 min, the reaction was
quenched by adding triethylamine (2 mL). The solvent was
removed, and the residue was purified by column chromatography
on silica gel using dichloromethane/petroleum ether as the eluent.
Recrystallization from dichloromethane/ethanol gave a purple solid
(0.40 g, 31%). 1H NMR (600 MHz, CDCl3):
d 10.17 (s, 2H), 9.58 (d, 4H),
9.41 (d, 4H), 5.01 (t, 4H), 2.55 (m, 4H),1.81 (m, 4H),1.55 (m, 4H),1.37
(m, 4H), 1.30 (m, 8H), 0.88 (t, 6H), ꢀ2.92 (br, 2H). MALDI-TOF: m/
z ¼ 535.5 (Mþ).
3.3. 5,15-Dibromo-10,20-dioctylporphyrin (4)
Porphyrin 3 (2.86 g, 4.4 mmol) was dissolved in 300 mL chlo-
roform (40 mL), and then NBS (1.60 g, 9 mmol) was added.
After stirring for 3 h, the reaction was quenched by addition of
acetone (10 mL). The solvents were removed, and the residue was
washed with ethanol three times and then recrystallized from
dichloromethane/ethanol to afford a purple solid (3.13 g, 88%). 1H
NMR (600 MHz, CDCl3): d 9.80 (d, 4H), 9.49 (d, 4H), 4.94 (t, 4H), 2.51

1866
X. Wang et al. / Polymer 53 (2012) 1864e1869
(m, 4H), 1.79 (m, 4H), 1.52 (m, 4H), 1.31 (m, 12H), 0.88 (m,
THF-d8): d 10.83 (s, 2H), 9.68 (d, 4H), 9.55 (s, 4H), 5.01 (t, 4H), 2.52
6H), ꢀ2.87 (s, 2 H). MALDI-TOF: m/z ¼ 693.4 (Mþ).
(m, 4H), 1.81 (m, 4H), 1.53 (m, 4H), 1.38 (m, 4H), 1.36 (m, 8H), 0.89
(m, 6H). MALDI-TOF: m/z ¼ 645.1 (Mþ).
3.4. 5,15-Dibromo-10,20-dioctylporphyrin zinc (5)
3.7. Synthesis of the polymer
To a solution of compound 4 (0.81 g, 1 mmol) in dichloro-
methane (500 mL) was added a solution of Zn(OAc)2$H2O (1.1 g,
5 mmol) in methanol (30 mL). The reaction mixture was stirred at
room temperature over night. Evaporation of the solvent and
washing three times with ethanol afforded a purple solid without
further purification.
Por monomer (324 mg, 0.5 mmol) and BT monomer (275 mg,
0.5 mmol) were put into a 100 mL two-neck flask, then 40 mL of
toluene and 20 mL triethylamine were added. The mixture was
stirred and purged with nitrogen for 10 min, and then Pd(PPh3)4
(30 mg, 0.025 mmol), CuI (19 mg, 0.1 mmol) was added. After being
purged for another 15 min, the mixture was heated at 60 ꢂC for
48 h. The terminal bromobenzene and phenylacetylene were added
as end cappers, with the phenylacetylene added first and the bro-
mobenzene added 12 h later. After stirring for another 12 h, the
reaction solution was cooled to room temperature. Then the reac-
tion mixture was added dropwise to 400 mL methanol, then
collected by filtration and washed with methanol. The black solid
was filtered into a Soxhlet funnel and extracted by methanol,
hexane, chloroform and THF successively. The polymer was
recovered from THF fraction and dried under vacuum for 1 day to
afford the target polymer PPoreBT as a black solid. (yield 41%,
Mn ¼ 7.5 kDa, Mw ¼ 16.7 kDa, PDI ¼ 2.2). 1H NMR (CDCl3, 600 MHz):
3.5. 5,15-Bis(trimethylsilylethynyl)-10,20-dioctylporphyrin zinc (6)
Compound 5 (0.87 g,1 mmol) was dissolved in THF (100 mL) and
triethylamine (50 mL) was added. The mixture was purged with
nitrogen for 10 min. Then Pd(PPh3)2Cl2 (35 mg, 0.05 mmol), CuI
(10 mg, 0.05 mmol), and trimethylsilylacetylene (0.4 g, 5 mmol)
were added. Then the mixture was purged with nitrogen for
another 15 min. After stirring at room temperature for 3 days under
nitrogen, the solvent was removed under reduced pressure. The
residue was purified by column chromatography (silica gel, CH2Cl2/
petroleum ether) to afford a purple solid (0.624 g, 79%). 1H NMR
d
10.00 (br, 4H), 9.71 (br, 4H), 5.11 (br, 4H), 4.27 (br, 4H), 2.49 (br,
(600 MHz, CDCl3):
d 9.49 (s, 4H), 9.22 (s, 4H), 4.69 (s, 4H), 2.35 (t,
4H), 2.00e0.91(br, 56H). Anal. Calcd for (C62H76N6O2SZn)n: C, 71.90;
H, 7.34; N, 8.12. Found: C, 71.42; H, 7.48; N, 8.09.
4H), 1. 76 (m, 4H), 1.51 (m, 4H), 1.42 (m, 8H), 1.11 (m, 4H), 0.90 (m,
6H), 0.61 (s,18H).
3.6. 5,15-Diethynyl-10,20-dioctylporphyrin zinc (Por)
4. Results and discussion
Tetrabutylammonium fluoride (0.88 g, 75% in water) was added
to a stirred solution of porphyrin 6 (1.00 g, 1.26 mmol) in THF
(100 mL). After stirring for 30 min, water was added to quench the
reaction. The solution was extracted with chloroform, washed with
water and dried over anhydrous MgSO4. After evaporation of the
solvent, the residue was recrystallized from dichloromethane/
ethanol to afford a purple solid (0.55 g, 67%). 1H NMR (600 MHz,
4.1. Syntheses of monomers and polymer
The synthetic routes of monomers and corresponding polymer
are outlined in Schemes 2 and 3, respectively. Monomer BT was
synthesized according to our previously proposed procedure [33].
Dipyrromethane 2 was synthesized by condensation of pyrrole
with formaldehyde, which was generated by cracking
Scheme 2. Synthetic routes of the monomers.a

X. Wang et al. / Polymer 53 (2012) 1864e1869
1867
Scheme 3. Synthetic route of the polymera.
4.2. Optical properties
Fig. 1 shows the absorption spectra of the polymer in THF
solution and solid thin film on a quartz plate. Table 1 summarizes
the optical data, including the absorption peak wavelengths (labs),
absorption edge wavelengths (lonset), and the optical band gap
ðEgoptÞ. In THF solution, the polymer exhibited two peaks centered at
456 and 818 nm, which is a typical absorption profile of Soret band
and Q-bands for porphyrin compounds. In solid film, the absorption
spectrum was expanded to 950 nm with an enhanced Q-band due
to the aggregation of the porphyrin rings. The optical band gap
determined from onset of the absorption of PPoreBT film was
1.34 eV. Compared with other porphyrin derivates based polymers,
PPoreBT exhibited very broad absorption spectrum and extremely
Fig. 1. Normalized absorption spectra of the PPoreBT in THF solution and film on
a quartz plate.
paraformaldehyde at 160 ꢂC, in the presence of TFA. New inter-
mediate trans-substituted porphyrin 3 was synthesized in 31% yield
by acid-catalyzed condensation of dipyrromethane with 1-decyne,
followed by oxidation with 2, 3-dichloro-5,6-dicyano-1,4-benzo-
quinone (DDQ) at room temperature, similar to Lindsey’s method
[34]. Coordination reaction with zinc acetate after bromination of 3
with NBS was taken to obtain zinc dibromoporphyrin 5 in high
yield. Monomer diethynylporphyrin
6 was synthesized by
Sonogashira-coupling reaction between zinc dibromoporphyrin 5
and trimethylsilylacetylene (TMSA) in high yield. Finally, the pro-
tecting trimethylsilyl groups were removed with tetrabuty-
lammonium fluoride (TBAF) in room temperature to afford Por. All
new compounds have been characterized by NMR and/or MS. The
data are consistent with the proposed structures. The synthesis of
the polymer was carried out using palladium-catalyzed Sonoga-
shira-coupling between monomer Por and BT. All starting mate-
rials, reagents, and solvents were carefully purified, and all
procedures were performed under an air-free environment. The
structure of the polymer was confirmed by 1H NMR spectroscopy
and elemental analysis. PPoreBT has reasonable solubility in
common organic solvents such as THF, chlorobenzene and o-
dichlorobenzene. It can be readily processed to form smooth and
pinhole-free films upon spin-coating.
Fig. 2. Cyclic voltammogram of the polymer film on Pt electrode in 0.1 mol/L Bu4NPF6,
CH3CN solution with a scan rate of 100 mV/s.
Table 1
Optical properties of PPoreBT.
PPoreBT
labs (nm)
lonset (nm)
Egopt (eV)a
In THF
In films
457, 818
454, 790
899
925
e
1.34
a
Band gap estimated from the onset wavelength (lonset) of the optical absorption:
Egopt ¼ 1240/lonset
.
Fig. 3. XRD images of spin-coated films.

1868
X. Wang et al. / Polymer 53 (2012) 1864e1869
Fig. 4. AFM images (2 ꢁ 2
m
m2) of spin-coated films: (a) before and (b) after annealing at 140 ꢂC.
strong Q-band absorption. This is benefit from intramolecular
charge transfer between the Por and BT moieties. These results
demonstrate that the employment of electron deficient BT unit to
construct donor-acceptor structure can observably broaden the
absorption spectrum and enhance the Q-band absorption of
porphyrin-based polymers.
Cyclic voltammogram of the polymer film is shown in Fig. 2. The
onset oxidation potential (Eox) and onset reduction potential (Ered
)
of PPoreBT are 0.35 V vs. Ag/Agþ and ꢀ1.08 V vs. Ag/Agþ respec-
tively. The HOMO and LUMO energy levels of the polymer are
calculated from the onset oxidation potential and the onset
reduction potential according to the equations [36]:
HOMO ¼ ꢀeðEox þ 4:71ÞðeVÞ
LUMO ¼ ꢀeðEred þ 4:71ÞðeVÞ
The calculated HOMO and LUMO energy levels of the polymer
are ꢀ5.06 eV and ꢀ3.63 eV, respectively. The electrochemical band
gap of the polymer ðEgopt ¼ 1:43eVÞ is well matched with its optical
band gap within the experimental error.
4.3. Electrochemical properties
Cyclic voltammetry has been employed and considered as an
effective tool in investigating electrochemical properties of conju-
gated oligomers and polymers [35]. From the onset oxidation and
reduction potentials in the cyclic voltammogram, energy levels of
HOMO and the lowest unoccupied molecular orbital (LUMO) can be
readily estimated, which correspond to ionization potential (IP) and
electron affinity (EA), respectively [9].
4.4. Film morphology and characteristics
The morphology and crystalline characteristics of the spin-
coated films of the polymer with or without annealing were
investigated by X-ray diffraction (XRD) and atomic force micros-
copy (AFM), respectively. Fig. 3 shows the XRD patterns of spin-
coated thin films of PPoreBT. It can be observed that the as-spun
film is amorphous, and the annealed film shows clear peaks,
which is indicative of improved molecular ordering. As shown in
the AFM images (Fig. 4), the morphology of the thin films
undergoes obvious changes with annealing. When annealed at
140 ꢂC for 2 h, the grain size increased and thus the mobility
improved.
4.5. Field-effect transistor properties of the polymer
Fig. 5 shows the typical output and transfer curves of OFET
device with PPoreBT as the active layer. The performances of the
polymer based devices are summarized in Table 2. The output
behavior closely followed the metal-oxide semiconductor FET
gradual-channel model with very good saturation (Fig. 5a). The
transfer characteristics of PPoreBT based devices showed a low
drain current at zero gate voltage (Fig. 5b), which shows its high air
stability due to the low HOMO (ꢀ5.06 eV) energy level. Without
Table 2
FET properties of devices with the polymer films spin-coated on OTS-Modified SiO2/
Si substrates.
PPoreBT
m
(cm2/V$s)
Ion/Ioff
VTH(V)
Without annealing
Annealed at 140 ꢂC
1.3 ꢁ 10ꢀ6
140
104
0
2
4.3 ꢁ 10ꢀ5
Fig. 5. (a) Output and (b) transfer characteristics of top-contact OFET using PPoreBT
as the active layer (annealed at 140 ꢂC).

X. Wang et al. / Polymer 53 (2012) 1864e1869
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annealing, the OFET with PPoreBT as the active layer showed
a mobility of 1.3 ꢁ 10ꢀ6 cm2/V$s in the saturation regime, together
with an on/off ratio of 140 when measured under ambient condi-
tions. Annealing the devices at 140 ꢂC for 30 min led to improved
charge carrier mobility of up to 4.3 ꢁ 10ꢀ5 cm2 Vꢀ1 sꢀ1 with an on/
off current ratio of 104 and a threshold voltage (VTH) of 2 V. The
charge carrier mobility is two orders of magnitude higher than that
of non-DeA porphyrinediacetylene copolymer [10]. These results
demonstrate that carrier mobility of prophyrin-based conjugated
polymers could be efficiently increased by intramolecular charge
transfer. High carrier mobilities could be obtained from prophyrin-
based DeA copolymer systems through the manipulation of
intramolecular charge transfer.
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5. Conclusion
We designed and synthesized a novel porphyrin-based polymer-
DPP (PPoreBT). The polymer demonstrated good solubility in
common organic solvents and broad absorption spectrum with
extremely enhanced Q-band absorption. The HOMO and LUMO
energy levels of the polymer are ꢀ5.06 eV and ꢀ3.63 eV, respectively.
The solution-processed organic field-effect transistors were fabri-
cated with bottom gate/top-contact geometry. The hole mobility of
PPoreBT reached 4.3 ꢁ10ꢀ5 cm2 Vꢀ1 sꢀ1 with an on/off current ratio
of 104. This mobility is one of the highest values for porphyrin-based
polymers. These results demonstrate that electronic and optoelec-
tronic properties of porphyrin-based conjugated copolymers could
be efficiently tuned by intramolecular charge transfer. High FET
carrier mobilities could be obtained from prophyrin-based DeA
copolymer systems through the manipulation of intramolecular
charge transfer. Most importantly, this work opens up a new path to
design high-performance porphyrin-based materials.
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This work was supported by Beijing Natural Science Foundation
(No. 2122047). We thank Professor Yongfang Li for his help with the
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