Two Anthracene-Based Copolymers as the Hole-Transporting Materials for High-Performance Inverted (p-i-n) Perovskite Solar Cells

Article abstract of DOI:10.1021/acs.macromol.8b00919

Two anthracene-based copolymers, the thiophene-bridged carbazole-anthracene copolymer (abbreviated as PCBZANT) and the thiophene-bridged triphenylamine-anthracene copolymer (abbreviated as PTPAANT), have been developed as the hole-transporting materials (HTMs) for the inverted perovskite solar cells. They were thermally stable with decomposition temperatures of 435 and 420 °C. The High Occupied Molecular Orbitals (HOMO) of -5.15 and -5.24 eV of two copolymers facilitated the hole carriers transfer from the perovskite layer (CH₃NH₃PbI₃, HOMO: -5.4 eV) in contrast to poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS, HOMO: -4.9 eV). The solar cell with PCBZANT (abbreviated as the PCBZANT device) showed the highest power conversion efficiency (PCE) of 15.50%, while the cell with PTPAANT (abbreviated as the PTPAANT device) showed the highest PCE of 14.52%, with increases of 36.2% and 27.6%, respectively, relative to the PEDOT:PSS device. The thorough analysis disclosed that the high performance was mainly ascribed to the enhanced open-circuit voltage (V_OC) and short-circuit current density (J_SC), being contributed from the efficient hole-carrier extraction, the high hole mobility of two copolymers, and the high-quality perovskite film with large crystal size and less defect. With strong absorption in the range of 350-500 nm, the polymers decreased the destruction of UV-radiation on the perovskite layer as UV-filters and improved the stability of the inverted cells.

Full text of DOI:10.1021/acs.macromol.8b00919

Article
pubs.acs.org/Macromolecules
Cite This: Macromolecules XXXX, XXX, XXX−XXX
Two Anthracene-Based Copolymers as the Hole-Transporting
Materials for High-Performance Inverted (p-i-n) Perovskite Solar
Cells
Tong Tong,† Chao Tan,† Tina Keller,‡ Bobo Li,† Chaoyue Zheng,† Ullrich Scherf,‡ Deqing Gao,*,†
and Wei Huang*,†
†Jiangsu National Synergistic Innovation Centre for Advanced Materials (SICAM), Key Laboratory of Flexible Electronics (KLOFE)
& Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing 211816,
People’s Republic of China
‡
̈
Macromolecular Chemistry Group, Bergische Universitat Wuppertal, Gaußstraße 20, Wuppertal D-42119, Germany
S
* Supporting Information
ABSTRACT: Two anthracene-based copolymers, the thiophene-bridged
carbazole-anthracene copolymer (abbreviated as PCBZANT) and the
thiophene-bridged triphenylamine-anthracene copolymer (abbreviated as
PTPAANT), have been developed as the hole-transporting materials
(HTMs) for the inverted perovskite solar cells. They were thermally stable
with decomposition temperatures of 435 and 420 °C. The High Occupied
Molecular Orbitals (HOMO) of −5.15 and −5.24 eV of two copolymers
facilitated the hole carriers transfer from the perovskite layer (CH3NH3PbI3,
HOMO: −5.4 eV) in contrast to poly(3,4-ethylenedioxythiophene):polys-
tyrenesulfonate (PEDOT:PSS, HOMO: −4.9 eV). The solar cell with
PCBZANT (abbreviated as the PCBZANT device) showed the highest
power conversion efficiency (PCE) of 15.50%, while the cell with
PTPAANT (abbreviated as the PTPAANT device) showed the highest
PCE of 14.52%, with increases of 36.2% and 27.6%, respectively, relative to the PEDOT:PSS device. The thorough analysis
disclosed that the high performance was mainly ascribed to the enhanced open-circuit voltage (VOC) and short-circuit current
density (JSC), being contributed from the efficient hole-carrier extraction, the high hole mobility of two copolymers, and the
high-quality perovskite film with large crystal size and less defect. With strong absorption in the range of 350−500 nm, the
polymers decreased the destruction of UV-radiation on the perovskite layer as UV-filters and improved the stability of the
inverted cells.
on hole-transporting materials utilized in PSC have been
reported.9−11
INTRODUCTION
■
To meet the energy requirement of industrial development,
people turn their focus to the efficient utilization of sustainable
energy such as solar energy. Since the first report in 2009,1
perovskite solar cells (PSCs) have attracted much attention in
the scientific and industrial communities because of the rapid
advance, outstanding performance, and low production
costs.2−4 With the development of the traditional cell structure
(n-i-p), the inverted cell structure (p-i-n) is attractive because
of the convenient production process, many commercial
possibilities, and the chance of having improved efficiency
and structural diversification. PEDOT:PSS, a commonly used
HTM in inverted PSCs, is highly conducting, transparent, and
stable.5,6 However, the HOMO level (−4.9) of PEDOT:PSS
does not well match with that (−5.4 eV) of perovskite
Carbazole possesses a strong electron-donating ability and is
a desired building block for effective HTMs,12−15 for example,
poly(9-vinylcarbazole) (PVK),16 copolymers poly-[[9-(1-oc-
tylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-ben-
zothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT),17 and
poly[N-9-hepta-decanyl-2,7-carbazole-alt-3,6-bis(thiophen-5-
yl)-2,5-dioctyl-2,5-dihydropyrrolo[3,4-]pyrrole-1,4-dione]
(PCBTDPP).18 Triphenylamine and its derivatives are highly
hole-transporting and have a well-matching energy level with
perovskite.19−21 Polytriaylamine (PTAA) has the hole mobility
between 10−2 and 10−3 cm2 V−1 s−1. The solar cell with the
photoactive formamidinium lead iodide (FAPbI3) and the
hole-transporting PTAA presented a PCE of 20.2%.21
Anthracene has an electron-donating ability and a large
(CH3NH3PbI3), and the solar cell exhibits relatively lower VOC
.
In addition, acid PEDOT:PSS may destroy the adjacent
materials.7,8 So the researchers have put effort into developing
hole-transporting candidates as a top priority. Review papers
Received: April 30, 2018
Revised: August 28, 2018
© XXXX American Chemical Society
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Scheme 1. Reaction Routes of Two Copolymers PCBZANT and PTPAANT
planarity, which can improve the structural ordering benefiting
charge transport.22,23 Its derivatives have been reported in bulk
heterojunction organic solar cells.24−26 A series of narrow band
gap conjugated copolymers with 2,6-linked anthracene donor
units and benzo[c][1,2,5]thiadiazole acceptor units were
utilized in polymer solar cells.27 A 9,10-linked anthracene-
based small molecule was utilized as a hole-transporting
material for perovskite solar cell.28 To our knowledge, there is
no report on anthracene-based polymers as HTMs for PSCs.
In our work, by making use of the favorite features, high
mobility and energy matching from carbazole and triphenyl-
amine units and well-ordered packing from anthracene units,
we elaborately designed two hole-transporting 2,6-linked
anthracene-based copolymers, a thiophene-linked carbazole
and anthracene copolymer PCBZANT and a thiophene-linked
triphenylamine and anthracene copolymer PTPAANT
(Scheme 1). Triphenylamine or carbazole component offers
a suitable HOMO energy-level matching to perovskite and
benefits the hole-carrier transporting between the hole-
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Figure 1. (a) Normalized UV−vis absorption spectra and (b) fluorescence spectra of PCBZANT and PTPAANT in CB solution and in film state.
transporting layer (HTL) and the perovskite layer. Anthracene
component is supposed to order the chain packing and
improve the carrier transporting. The long alkyl side chains
were introduced on the carbazole N atom and thiophene units
to increase the solubility and crystallinity. The structure and
photophysical properties of PCBZANT and PTPAANT have
been characterized by nuclear magnetic resonance (NMR), gel
permeation chromatography (GPC), UV−vis, fluorescence
spectroscopy, thermogravimetric analysis (TGA), differential
scanning calorimetry (DSC), and ultraviolet photoelectron
spectroscopy (UPS). The film morphology was studied by X-
ray diffraction (XRD), atomic force microscopy (AFM), and
scanning electron microscopy (SEM) measurements. The
wetting property was determined by a microscopic contact
angle meter. The photovoltaic properties were determined
under 100 mW cm−2 illumination of simulated AM 1.5G
sunlight.
KOH to give 4-(2-octyloxy phenyl) diphenylamine (8) in a
yield of 60%. Following the same method for the synthesis of
4, the bromination product, 4-bromo-N-(4-bromophenyl)-N-
(4-(octyloxy)-phenyl)benzenamine (9), was subjected to a
Still coupling reaction to give 4-(octyloxy)-N,N-bis(4-(thio-
phen-2-yl)phenyl)aniline (10). 10 was brominated with NBS,
and 4-(5-bromothiophen-2-yl)-N-(4-(5-bromothiophen-2-yl)-
phenyl)-N-(4-(octyloxy)phenyl)aniline (M3) was achieved in
a yield of 85%. The copolymer PCBZANT was synthesized
from Suzuki coupling reaction between M1 and M2 in a
microwave reactor in a yield of 56%. The number-average
molecular weight (Mn) of PCBZANT was found to be 30 400
g/mol with a PDI of 2.04. The copolymer PTPAANT was
obtained via the same reaction method as the preparation of
PCBZANT from two monomers M2 and M3 in a yield of 84%.
The number-average molecular weight (Mn) of PTPAANT
was found to be 13 400 g/mol with a PDI of 1.87.
Optical Absorption and Fluorescence Properties.
UV−vis spectroscopic property was characterized in chlor-
obenzene (CB) solution and in film. As demonstrated in
Figure 1a, in solution PCBZANT had the absorption at 397,
457, and 485 nm, and PTPAANT had the absorption at 359,
405, 465, and 487 nm. The three absorption peaks from 397 to
487 nm of PCBZANT or PTPAANT originated from
anthracene units, and the absorption of 359 nm originated
from triphenyl-thiophene moieties. As is well-known, the
perovskite solar cell degrades under UV radiation.7 Two hole-
transporting polymers had strong absorption in the range of
350−500 nm. Being located at the front side of the inverted
device, they can decrease the destruction of UV-radiation on
the perovskite layer as UV-filters and improve the cell stability,
as reported in the literature.29
In solution, PTPAANT had the onset at 531 nm and
PCBZANT had the onset at 517 nm. In films, both polymers
presented bathochromic absorption; especially PCBZANT had
a large onset shift of 33 nm. It can be deduced that PCBZANT
was prone to orderly interchain arrangement in the solid state,
facilitating the charge mobility. This conclusion was confirmed
by the fluorescence characterization of two polymers (Figure
1b). PCBZANT presented an emission maximum at 512 nm,
and PTPAANT presented an emission maximum at 551 nm.
However, PCBZANT showed a larger Stokes shift in film than
in solution in contrast to PTPAANT.
RESULTS AND DISCUSSION
■
Synthesis and Characterization. Scheme 1 demonstrates
the synthetic routes for three monomers (M1, M2, and M3)
and two copolymers (PCBZAAN and PTPAANT). The
monomer M1 has a carbazole backbone. The starting material
4,4′-dibromo-1,1′-biphenyl was first nitrified. The obtained
4,4′-dibromo-2-nitro-1,1′-biphenyl (1) was reacted with
triethylphosphate to deliver 2,7-dibromo-9H-carbazole (2) in
a yield of 87%. The alkylation of 2 with 1-bromooctane gave
2,7-dibromo-9-octyl-9H-carbazole (3), which was subjected to
a Still coupling reaction with 2-tributylstannythiophene to
prepare 9-octyl-2,7-di(thiophen-2-yl)-9H-carbazole (4) in a
yield of 70%. 4 was brominated with NBS to generate 2,7-
bis(5-bromothiophen-2-yl)-9-octyl-9H-carbazole (M1). The
monomer M2 has an anthracene backbone. 2,6-Diaminoan-
thracene-9,10-dione was brominated to give 2,6-dibromoan-
thracene-9,10-dione (5), which reacted with 2-dodecylthio-
phene in the presence of n-BuLi to give 5,5′-(2,6-
dibromoanthracene-9,10-diyl)bis(2-dodecylthiphene) (6) in a
yield of 58%. 2,2′-(9,10-Bis(5-dodecylthiophen-2-yl)-
anthracene-2,6-diyl)-bis(4,4,5,5-tetramethyl-1,3,2-dioxaboro-
lane) (M2) was obtained from the reaction between 6 and
bis(pinacolato)diboron using Pd(pddf)Cl2 catalyst in a yield of
70%. The monomer M3 has a triphenylamine backbone. The
starting material 4-iodophenol and octyl bromide reacted to
generate 1-iodo-4-octyloxybenzene (7), which reacted with
diphenylamine in the presence of CuCl, phenathroline, and
Thermal Analysis. The thermal property was analyzed
with thermogravimetric analysis (TGA) and differential
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Figure 2. AFM topographic images and water contact angles of pristine PCBZANT (a), PCBZANT with the additive m-MTDATA (b), pristine
PTPAANT (c), and PTPAANT with m-MTDATA (d) and PEDOT:PSS (e) films (RMS unit: nm). Inset: Chemical structure of the additive m-
MTDATA. The films were prepared by spin coating each dichlorobenzene solution and thermally annealing at 100 °C for 20 min on ITO
substrates.
scanning calorimetry (DSC) at 10 K min−1 under flowing
argon. As shown in Figure S19, corresponding to initial 5% of
weight loss, PCBZANT and PTPAANT exhibited superior
thermal stability with decomposition temperatures (Td) of 435
and 420 °C, respectively, much stable than 2,6-linked donor−
acceptor anthracene-benzo[c][1,2,5]thiadiazole copolymer.27
In Figure S20, DSC measurement showed a similar glass
transition temperature (Tg) at 77 and 80 °C, for PCBZANT
and PTPAANT, respectively, in the first heating scan. They
presented a similar Tg, being in agreement with the report in
the case of the carbazole-based copolymer and the triphenyl-
based copolymer.30
Film Characterization. The morphology and quality of
the films were analyzed with atomic force microscopy (AFM)
measurement. As shown in Figure 2a and c, the pristine
PCBZANT and PTPAANT films both had a high root-mean-
square (RMS) roughness of 2.04 and 2.66 nm, respectively.
4,4′,4″-Tris[phenyl(m-tolyl)amino]triphenylamine (m-
MTDATA), as an additive for PTAA,31 was utilized as an
additive as well in the study. After various blending
concentrations of m-MTDATA were tested, the PCBZANT
with 30 wt % m-MTDATA presented the roughness 1.21 nm,
even smaller than 1.45 nm of PEDOT:PSS film (Figure 2b
versus e). PTPAANT film with 20% m-MTDATA became
homogeneous as well with a roughness of 1.72 nm (Figure 2d).
The wetting property changed correspondingly. As shown in
Figure 2, from the pristine film to the m-MTDATA-blending
film, the contact angle was decreased from 108.0° to 96.4° for
the PCBZANT film, and from 105.6° to 95.5° for the
PTPAANT film, respectively, being more hydrophobic than
the PEDOT:PSS film with a contact angle of 48.4°.
Charge Transport Properties. On the basis of the Mott−
Gurney space-charge limited current (SCLC) method,32 the
hole mobility was evaluated by using the device with the
structure of ITO/PEDOT:PSS/PCBZANT or PTPAANT/
MoO3/Ag (seen in Figure 3). According to the Mott−Gurney
law calculation, PCBZANT and PTPAANT presented the
hole mobility of 1.31 × 10−4 and 5.89 × 10−5 cm2 V−1 s−1,
respectively (Figure 3a and b). After 30 and 20 wt % m-
MTDATA were blended, the hole mobilities were increased to
7.15 × 10−3 and 5.86 × 10−3 cm2 V−1 s−1 for PCBZANT and
PTPAANT, respectively (Figure 3c and d), being higher than
the well-known spiro-OMeTAD with dopants.33 It indicated
that blending the additive m-MTDATA distinctively enhanced
the film quality of two copolymers and increased the hole
mobility by 1−2 orders of magnitude.
Photovoltaic Properties of Perovskite Solar Cells. The
framework of the inverted perovskite solar cell was illustrated
in Figure 4d. Phenyl-C61-butyric acid methyl ester (PC61BM)
and fullerene (C60) worked as the electron transporting
materials (ETMs). Bathocuproine (BCP) functioned as the
buffer layer. As indicated above, blending m-MTDATA much
improved the morphology and carrier mobility of the
PCBZANT and PTPAANT films, so PCBZANT and
PTPAANT with m-MTDATA additive composed the hole-
transporting layers, and the corresponding devices were
abbreviated to PCBZANT device and PCBZANT device
relative to the PEDOT:PSS-based control device (abbreviated
as PEDOT:PSS device). The fabrication of the cell with the
structure of ITO/HTM/CH3NH3PbI3/PC61BM/C60/BCP/Al
was carried out according to the method we reported.34 The
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Figure 3. Hole mobility curves of pristine PCBZANT (a), pristine PTPAANT (b), PCBZANT with 30 wt % m-MTDATA (c), and PTPAANT
with 20 wt % m-MTDATA (d).
detailed device fabrication is available in the Supporting
Information.
performances between the PCBZANT device and PTPAANT
device, photogenerated carrier’s extraction, perovskite’s crys-
tallinity, and the front orbitals of two copolymers were
investigated.
The photovoltaic performances of the devices were
measured under AM 1.5G simulated sunlight irradiation
(100 mW cm−2). The cells were tested with different polymer’s
concentrations and with different blending ratios of m-
MTDATA. The photovoltaic parameters are compiled in
Tables S1−S4. Figure 4a presented the photocurrent density−
voltage (J−V) curves of the best-performance PCBZANT
device, PTPAANT device, and PEDOT:PSS device. In the
corresponding devices, PCBZANT film and PTPAANT film
had thicknesses of 16 and 12 nm, respectively. The device’s
cross-section image was presented in Figure S25. The data
were collected in Table 1. As compared to the PEDOT:PSS
device, which had a PCE of 11.38%, VOC of 0.92 V, JSC of 16.85
mA cm−2, and fill factor (FF) of 73.32%, the PCBZANT
device and the PTPAANT device had better performance.
When the concentration of PCBZANT was 3 mg/mL with 30
wt % m-MTDATA, the PCBZANT device presented an
optimal PCE of 15.50%, VOC of 0.95 V, JSC of 21.03 mA cm−2,
and FF of 77.50%. The best performance of the PTPAANT
device was observed when the concentration of PTPAANT
was 3 mg/mL with 20 wt % m-MTDATA. It possessed a PCE
of 14.52%, VOC of 1.0 V, JSC of 18.66 mA cm−2, and FF of
77.84%. It is worth noting that the photovoltaic parameters of
the PCBZANT device and PTPAANT device were improved
in contrast to those of the PEDOT:PSS device. Figure 4c
illustrated the incident photon-to-current conversion efficiency
(IPCE). The increasing order of IPCE of these devices was in
agreement with J−V results. To explore the different
Perovskite Crystallinity. A smooth and hydrophobic
surface is beneficial for the formation of high-quality perovskite
film.20,32 X-ray diffraction (XRD) measurement was used to
investigate the crystallinity of the perovskite film on the
different hole-transporting layers. As seen in Figure 5a and b,
as compared to three typical diffraction peaks of perovskite
crystal at around 14° (110), 28° (220), and 32° (310)35 on
PEDOT:PSS film, the crystals grown on PCBZANT and
PTPAANT films exhibited high-intensity and sharp peaks.
SEM measurement (Figure 5c−e) showed that the perovskite
crystals on PCBZANT and PTPAANT films were much larger
and more homogeneous as compared to those on PEDOT:PSS
film. The crystal dimension and quality are highly dependent
on the wetting property of the underlying layer according to
Huang’s report.36 The perovskite film on hydrophobic
PCBZANT and PTPAANT films with the additive m-
MTDATA possessed a larger crystal size and less defect,
which benefit the efficient photogenerated exciton’s trans-
porting and high-quality interface.36−38 It is to be noted that
the needle-like grains were observed in the SEM. These grains
were formed by an unbalanced DMF-involved complex system
in the preparation process of the perovskite film.39,40 Excess
PbI2 remaining in the film was proved by the 12.8° peak in
XRD. The needle-covered morphology was the main factor for
the obvious hysteresis of J−V curves presented in Figure 4a
and b.41
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Figure 4. (a) Current density−voltage (J−V) curves of PCBZANT device with reverse and forward scan directions; (b) J−V curves of PTPAANT
device with reverse and forward scan directions; (c) IPCE curves of PCBZANT device, PTPAANT device, and PEDOT:PSS device; and (d) cell
architecture of the inverted PSCs, where HTM is PCBZANT, PTPAANT, or PEDOT:PSS, and ETM is PC61BM/C60.
Table 1. Photovoltaic Parameters of the PCBZANT Device,
PTPAANT Device, and PEDOT:PSS Device
Energy-Level Analysis. From ultraviolet photoelectron
spectroscopy (UPS) measurement, the high occupied molec-
ular orbitals (HOMOs) of PCBZANT and PTPAANT were
found to be −5.15 and −5.24 eV, which is close to −5.26 eV of
9,10-linked anthracene-arylamine material28 (Figure S21). As
seen in Figure 6b, as compared to PEDOT:PSS (HOMO:
−4.9 eV), PCBZANT and PTPAANT had well-matching
HOMO levels with perovskite CH3NH3PbI3 (HOMO: −5.4
eV), benefiting the hole extraction from the perovskite layer
and overcoming the disadvantage of a relatively lower VOC in
the PEDOT:PSS-based inverted perovskite solar cells.
sweep
direction
VOC
(V)
JSC
PCE
(%)
HTM
(mA cm−2
)
FF (%)
PCBZANT
forward
reverse
forward
reverse
forward
reverse
0.91
0.95
0.95
1.00
0.92
0.92
21.40
21.03
19.22
18.66
16.89
16.85
58.22
77.50
56.60
77.84
60.99
73.32
11.36
15.50
10.48
14.52
9.47
PTPAANT
PEDOT:PSS
11.38
From the above-stated thorough studies, the high photo-
voltaic performance was attributed to three factors. First, the
two copolymers had deep HOMO levels, which contributed to
a high VOC value. Second, the HOMO levels of two
copolymers well matched with the perovskite layer and
facilitated effective hole extraction from the perovskite
layer.42,43 Third, blending with the additive m-MTDATA
both PCBZANT and PTPAANT layers had a high hole
mobility in the order of 10−3. Besides, the perovskite layer
above each PCBZANT and PTPAANT layer had high
crystallinity. In comparison, the PCBZANT device had higher
PCE than did the PTPAANT device, mainly being ascribed to
the fact that the PCBZANT device had a higher Jsc by 12.7%
relative to that of the PTPAANT device.
Photoluminescence of HTM/Perovskite Films. To
study the charge transfer property, we investigated the
photogenerated carrier’s extraction out of the perovskite film
above each HTL with photoluminescence (PL) and time-
correlated single-photon counting (TCSPC). Figure 6a
demonstrated the steady-state PL spectra of the perovskite
film. As compared to the perovskite/PEDOT:PSS system, the
perovskite film above PCBZANT or PTPAANT layer,
especially the film above PCBZANT layer, experienced clear
fluorescence quenching. As shown in Figure S23, excited by a
465 nm laser and fitted by two exponential decay functions,
TCSPC curves revealed the average PL lifetime of the
perovskite film of 15.35 ns for the PCBZANT system and
14.15 ns for the PTPAA system, much lower than 24.7 nm for
the PEDOT:PSS system. The results of the steady-state PL and
PL lifetime indicated that PCBZANT and PTPAANT as
HTMs can effectively extract hole carriers out of the perovskite
layer and decrease the carrier recombination.
Reproducibility and Longevity Stability of the Cells.
The reproducibility was tested with 10 individual devices (seen
in Figures 7 and S22). All of the devices based on these two
copolymers presented high reproducibility with an average
PCE of more than 13%. The device stability was studied by
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Figure 5. XRD patterns of the perovskite films above the layer of PCBZANT with the additive m-MTDATA versus above PEDOT:PSS layer (a)
and those above the layer of PTPAANT with m-MTDATA versus above PEDOT:PSS layer (b); SEM images of the perovskite films above the
layer of PCBZANT with m-MTDATA (c), PTPAANT with m-MTDATA (d), and PEDOT:PSS (e).
Figure 6. (a) Steady-state PL curves of the perovskite films above PCBZANT, PTPAANT, and PEDOT:PSS layers; and (b) energy-level diagram
of the functional materials.
recording PCE of the solar cells, which were stored in a
glovebox with time (Figure S24). After 30 days, the
PCBZANT device had PCE of 13.11% by decrease of 11.4%
relative to the initial 14.79%. In contrast, the PTPAANT
device lost 15.5%, and the control device lost 17.8%. Obviously
the PSCs based on PCBZANT and PTPAANT were more
stable than the PDOT:PSS-based solar cell. The high stability
could be attributed to the above-stated UV-blocking ability of
the two polymers.
each copolymer film became homogeneous and hydrophobic.
The hole mobility was enhanced to 10−3 cm2 V−1 s−1 in
increase of 1−2 orders of magnitude from the pristine film.
The cells presented high PCE, reproducibility, and long
lifetime. With the structure of ITO/HTM/CH3NH3PbI3/
PC61BM/C60/BCP/Al, the PCBZANT-based device achieved
a PCE of 15.50%, and the PTPAANT-based device obtained a
PCE of 14.52%, relative to 11.38% from the PEDOT:PSS-
based device. The improved performance was ascribed to the
more suitable work function and high hole mobility. The
perovskite film prepared on the top of each copolymer layer
had a large crystal size and less defects. It indicates that
PCBZANT and PTPAANT are two suitable hole-transporting
materials for the inverted perovskite solar cells.
CONCLUSIONS
■
In this study, we demonstrate two anthracene-based
copolymers as the hole-transporting materials for inverted
perovskite solar cells. By blending the additive m-MTDATA,
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Figure 7. Histogram of photovoltaic parameters of the PSCs based on PCBZANT and PEDOT:PSS.
employing organic charge-transport layers. Nat. Photonics 2014, 8,
128−132.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.macro-
mol.8b00919.
■
S
(3) You, J. B.; Hong, Z. R.; Yang, Y.; Chen, Q.; Cai, M.; Song, T. B.;
Chen, C. C.; Lu, S. R.; Liu, Y. S.; Zhou, H. P.; Yang, Y. Low-
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Experimental details, synthesis and NMR, device
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AUTHOR INFORMATION
Corresponding Authors
*E-mail: iamdqgao@njtech.edu.cn.
*E-mail: iamwhuang@njupt.edu.cn.
ORCID
Deqing Gao: 0000-0002-9920-3427
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS
■
This work was supported by the National Key Basic Research
Program of China under Grant 2015CB932200 (D.G. and
W.H.).
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