Phosphorous tetrabenzocorrolazine from its metal-free phthalocyanine precursor: Its facile synthesis, high fluorescence emission, efficient singlet oxygen formation, and promising hole transporting material

Article abstract of DOI:10.1016/j.dyepig.2020.108421

We have synthesized tetra(4-tert-butyl phenoxy)-tetrabenzocorrolazine phosphorous POTBC(β-OPB)₄, a functional π-conjugated macrocycle compound derived from corrole or corrolazine, by a one step procedure from its metal free phthalocyanine precu

Full text of DOI:10.1016/j.dyepig.2020.108421

Dyes and Pigments 179 (2020) 108421
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Dyes and Pigments
journal homepage: http://www.elsevier.com/locate/dyepig
Phosphorous tetrabenzocorrolazine from its metal-free phthalocyanine
precursor: Its facile synthesis, high fluorescence emission, efficient singlet
oxygen formation, and promising hole transporting material
Xulin Lua, Xian-Fu Zhangb,*
a Hebei Normal University of Science and Technology, Qinhuangdao, 066004, Hebei Province, China
b MPC Technologies, Hamilton, L8S 3H4, Ontario, Canada
A R T I C L E I N F O
A B S T R A C T
Keywords:
We have synthesized tetra(4-tert-butyl phenoxy)-tetrabenzocorrolazine phosphorous POTBC(β-OPB)4, a func-
Corrole
tional π-conjugated macrocycle compound derived from corrole or corrolazine, by a one step procedure from its
Singlet oxygen
Photosensitizer
Fluorescence
Excited triplet state
metal free phthalocyanine precursor. The product structure is characterized by UV–Vis absorption, MS, NMR and
IR spectral methods. We have also studied their fluorescence properties, excited triplet state formation, photo-
sensitized singlet oxygen production, and their application as undoped hole transporting layer (HTL) in perov-
skite solar cells (PSC). The results show that POTBC(β-OPB)4 is highly emissive (fluorescence quantum yield 0.60
in the red region which is little affected by solvent), it also exhibits significant singlet oxygen formation ability
(quantum yield 0.40 which is little influenced by solvent), and show remarkable power conversion efficiency
(15.8%) as undoped HTL. These facts suggest that POTBC(β-OPB)4 is a promising fluorescence imaging agent and
good singlet oxygen photosensitizer for photodynamic therapy of tumor. It is also a good candidate as undoped
hole transporting material for PSC.
1. Introduction
consideration, we have synthesized soluble phosphorous tetrabenzo-
corrolazine from its metal-free phthalocyanine precursor (Fig. 2), stud-
Functional
π-conjugated macro cycle compounds play key roles in
ied their photophysics, singlet oxygen photosensitizing capability, and
hole transporting material properties for metal halide perovskite solar
cells. The results indicate that the TBC is good singlet oxygen photo-
sensitizer as well as promising undoped photovoltaic hole transporting
material (HTM).
many aspects [1,2], such as chlorophyll in photosynthesis, porphyrins in
the production of hemoglobin responsible for carrying oxygen in the
blood throughout the entire body. Porphyrins, phthalocyanines and
their derivatives are the best known functional macro cycle compounds
which have been the research focus in chemistry, biology and materials
science [3,4]. Tetrabenzocorrolazine (or termed as tetrabenzo-
triazacorrole, abbreviated as TBC, Fig. 1) is a derivative from both
corrole and phthalocyanine, but its synthesis and properties are much
less explored [5–15]. Due to the missing of a nitrogen atom from its
phthalocyanine precursor, TBC is a trivalent ligand with smaller cavity.
TBC compounds show excellent light absorbing capability in the whole
UV–Visible region, in contrast to porphyrins absorbing weakly in the red
region and phthalocyanines absorbing weakly in the UV and green re-
gion, this makes TBC compounds good candidates for photosensitizers.
TBCs usually show lower oxidation potentials than corresponding
phthalocyanine which enable them potentially good electron donors and
hole transporting materials for photovoltaics. Taking these all into
2. Experimental section
2.1. Materials and instruments
4-nitro phthalonitrile, para-tert-butyl phenol, metal lithium, PBr3,
DMF, DMSO, lithium hydroxide, n-pentanol, acetic acid, chloroform,
methanol, pyridine and other solvents were purchased from Aladdin
Reagents. POTBC was home made and reported previously [16,17]. All
solvents for the synthesis were analytic grade. All solvents for the
spectral measurements were redistilled. The UV–Vis absorption spectra
were measured on a UV/vis spectrophotometer (Perkin Elmer Lambda
650). The emission spectra were measured on
a fluorescence
* Corresponding author.
E-mail addresses: zhangxianfu@tsinghua.org.cn, zhangxf111@hotmail.com (X.-F. Zhang).
https://doi.org/10.1016/j.dyepig.2020.108421
Received 19 January 2020; Received in revised form 1 April 2020; Accepted 1 April 2020
Available online 5 April 2020
0143-7208/© 2020 Elsevier Ltd. All rights reserved.

X. Lu and X.-F. Zhang
Dyes and Pigments 179 (2020) 108421
Fig. 1. Chemical structures and relations of corrole, corrolazine, tetrabenzocorrolazine and phthalocyanine.
Fig. 2. Chemical structures, abbreviations, and synthetic routes for the compounds in this study. (i): K2CO3/DMF; (ii): Li/n-pentanol/refluxing; (iii): PBr3/pyridine/
95 �C then CH3OH (1 M HCl).
spectrophotometer (FLS 920 of Edinburgh). NMR spectra were recorded
on a Bruker Ascend TM 500 MHz. Chemical shifts were reported as δ
values (ppm) with tetramethylsilane (TMS) as the internal standard.
purified by column chromatography (silica gel 300 mesh, eluent is
chloroform/methanol: 50/1). Blue solid, yield: 76 mg, 38%; mp: > 350
�C. IR (KBr)
ν
, cmÀ 1: 3432, 3290, 3036, 2958, 2903, 2866, 1601, 1508,
HRMS (high resolution mass spectrometer) was recorded on
a
1474, 1425, 1394, 1321, 1233, 1173, 1108, 1092, 1011, 928, and 827;
UV–Vis (CHCl3) λmax: 346, 610, 643, 669, and 703 nm. 1H NMR: δН
(CDCl3, 400 MHz), 7.57–7.67 (8H, m, Ar-H), 7.37–7.52 (12H, m, Ar-H),
7.27–7.32 (8H, m, Ar-H), 1.47 (36H, s, CH3) ppm. HRMS: C72H66N8O4,
calculated 1107.5241 [MþH]þ, found 1107.5262.
Thermo-Fisher Q-Exactive mass spectrometer. The FT-IR spectrometer
measurements of the devices were carried out by using a Nicolet NEXUS
870 FT-IR spectrometer to collect the FT-IR spectral data in the 700À
3600 cmÀ 1 range.
The details on the photophysics, singlet oxygen formation, and solar
cell device fabrication and characterization are given in electronic
supporting information.
2,6(7),10(11),14(15)-Tetra(p-tert-butyl phenoxy)-tetrabenzocor
rolazine phosphorous POTBC(β-OPB)4. This was prepared by the
procedure in Fig. 2. Pyridine (10 mL) containing H2Pc(β-OPB)4 (2.27 g,
2.05 mmol) was added into a 50 mL three-necked round-bottom flask,
which was equipped with a reflux condenser and a nitrogen gas inlet
tube. After 10 min nitrogen-purging, pyridine (10 mL) containing PBr3
(6.5 mL, 76 mmol) was added, the resulting mixture was heated at 95 �C
understirringandN2 for1h. Aftercoolingdown, 2mLCH3OHcontaining
1 M HCl was added, the mixture was poured into water and filtered, and
the solid was washed thoroughly with deionized water. The crude
product was dissolved in dichloromethane and purified by column
chromatography on silica gel using THF-dichloromethane (5:95) as
eluent. Greensolid, yield:1.05g, 43%. UV/Vis (DMF)λmax 448, 603, 638,
and 657 nm. 31P NMR: δP (CDCl3, 400 MHz), À 188 ppm. 1H NMR: δН
(CDCl3, 400 MHz), 9.54–10.0 (4H, m, Pc-H), 8.90–9.28 (4H, m, Pc-H),
7.89–8.18 (4H, m, Pc-H), 7.48–7.66 (8H, m, phenyl-H), 7.28–7.41 (8H,
m, phenyl-H), 1.41–1.53(36H, m, tert-butyl), 1.25–1.32(6H, s, CH3).
HRMS m/z (ESI) for C74H71N7O6P [MþH]þ calcd. 1184.5203, found
1183.5190.
2.2. Synthesis
4-(para-tert-butyl phenoxy) phthalonitrile. In DMSO (30 ml)
containing para-tert-butylphenol (1.50 g, 10 mmol) and 4-nitro-phthalo-
nitrile (1.73 g, 10 mmol), lithium hydroxide (0.42 g, 10 mmol) was
added and stirred at 50 �C for 12 h. After that, the solution was cooled
down and poured into aqueous solution (10% NaCl, 100 ml), the
precipitated solid was filtered and washed with deionized water, and the
light yellow solid product was dried and recrystallized from ethanol.
White crystals, yield, 2.01 g, 73%, m.p. 113–115 �C. 1H NMR: δН
(CDCl3, 400 MHz), 6.95–7.70 (7H, m, Ar-H), 1.34 (9H, s, CH3). MS:
C
18H16N2O, calculated 276.13 [Mþ], found 276.21.
2,6(7),10(11),14(15)-Tetra(p-tert-butyl phenoxy) metal-free
phthalocyanine H2Pc(β-OPB)4. In n-pentanol (5 mL) containing 40
mg metal lithium, argon was bubbled for 10 min, then the solvent was
refluxed so that all the metal was converted to C5H11OLi. 4-(4-Tert-
butylphenoxy) phthalonitrile (200 mg, 0.72 mmol) was then added
quickly. The reaction was continued under argon, stirred and refluxed
for 8 h. Acetic acid was then added (0.8 mL) to the cooled solution. The
solvent was removed under reduced pressure and then the residue was
2

X. Lu and X.-F. Zhang
Dyes and Pigments 179 (2020) 108421
Fig. 3. Normalized UV–Vis absorption spectra (left) and fluorescence spectra (right), sample concentration ~10 μM. For fluorescence measurements, the excitation
wavelength is 610 nm.
Table 1
The photophysical parameters in different solventsa.
H2Pc(β-OPB)4
POTBC(β-OPB)4
POTBC
CCl4
THF
CCl4
THF
DMF
DMF
λmax, abs [nm]
341,666,705
710
340,665,701
709
449, 605,638,663
440,597,626,653
448,603,638,657
440,627,653
664
λmax, em [nm]
669
135
0.57
3.34
1.14
0.17
ND
665
666
206
0.63
3.83
1.2
Stokeʼs shift [cmÀ 1
]
100
161
276
254
Φf
0.41
0.39
0.62
3.72
1.21
0.17
0.41
0.36
τf [ns]
6.23
5.85
3.55
χ2
1.1
1.11
1.17
kf, 108 sÀ 1
ΦΔ
0.66
0.67
0.16
0.39
0.10
ND
0.13
0.43
a
ND ¼ not determined.Table 2
3. Results
3.1. Synthesis and structural characterization
Fig. 2 shows the three step synthetic path to POTBC(β-OPB)4 from 4-
nitro phthalonitrile. POTBC(β-OPB)4 is formed by insertion of a P5þ into
the cavity of its precursor H2PC(β-OPB)4, in the process a nitrogen atom
is eliminated, so that the cavity size of the macrocycle is reduced to
better coordinate the P(V) ion due to the very small size of P5þ ion (0.38
Å). POTBC(β-OPB)4 shows a much better solubility in organic solvents
than unsubstituted POTBC so that the purification by column chroma-
tography on silica gel is much more friendly and easier.
For the characterization of phthalocyanines and their analogues,
UV–Vis, MS spectral methods are usually considered more informative
[18], because the signal of 1H NMR for aromatic H is overlapped
severely. For H2Pc(β-OPB)4, UV–Vis, HRMS, and 1H NMR spectra are
fully consistent with its chemical structure (Fig. S1 and Fig. S2, sup-
porting information).
The absorption spectra of POTBC(β-OPB)4 are very similar to that of
POTBC except a slight red shift (Fig. 3) which confirms the product
structure. On the other hand, the absorption spectra of POTBC(β-OPB)4
are very different from that of its phthalocyanine precursor, in the sense
that a very strong new band appears at ~ 450 nm. The mass spectrum of
POTBC(β-OPB)4 shows a molecular ion peak at 1183.6 (Fig. S3, sup-
porting information), consistent with the calculated value 1183.5. The
presence of P atom is confirmed by 31P NMR in which a peak at À 188
ppm is observed (Fig. S5, supporting information). 1H NMR spectra of
POTBC(β-OPB)4 is also consistent with its structure (Fig. S4, supporting
information).
Fig. 4. Fluorescence decay (680 nm) with excitation at 672 nm (50 ps diode
laser) in THF, sample concentration ~10 μM. Data fitting to monoexponential
function using deconvolution method, the chi squared value is between 1.00
and 1.15.
3.2. Fluorescence properties
Fig. 3 also shows the fluorescence spectra. The fluorescence emission
spectrum of POTBC(β-OPB)4 is very similar to that of POTBC except a
slight red shift (Fig. 3). The emission spectra of POTBC(β-OPB)4 show
3

X. Lu and X.-F. Zhang
Dyes and Pigments 179 (2020) 108421
Fig. 5. Left: Time resolved excited triplet state (T1-Tn) transient absorption spectra of POTBC(β-OPB)4 in N2-saturated THF with OPO laser excitation at 655 nm (4 ns
and 10 mJ per pulse), sample concentration ~20 M. Middle: The decay of T1 state at 465 nm and the rise of ground state at 650 nm for POTBC(β-OPB)4 in N2-
saturated THF with OPO laser excitation at 655 nm (4 ns and 10 mJ per pulse), sample concentration ~10 M. Right: the decay of T1 state at 465 nm for POTBC
(β-OPB)4 in air-saturated THF with OPO laser excitation at 655 nm (4 ns and 10 mJ per pulse), sample concentration ~5 M.
μ
μ
μ
emission maxima within 665–670 nm in different solvents (Table 1)
which are blue shifted about 40 nm from its Pc precursor. The Stokes
shift are all very small, indicating their chemical structures are very rigid
and little changed by photo excitation even in the liquid solvents.
For POTBC, the measured fluorescence properties are consistent with
the reported values [16,17]. POTBC(β-OPB)4, however, exhibits higher
fluorescence quantum yield (Φf ¼ 0.60 � 0.03) which is little affected by
solvent nature, the Φf value is also significantly higher than that of H2Pc
(β-OPB)4 and POTBC (Table 1). The fluorescence decay is all mono-
exponential (Fig. 4), indicating that only one emitting species exists. The
calculated fluorescence lifetime of POTBC(β-OPB)4 (τf ¼ 3.63 � 0.29 ns)
is also longer than that of POTBC. The calculated fluorescence radiation
constant (kf ¼ Φf/τf) of POTBC(β-OPB)4 is almost not affected by solvent,
but the value 0.17 � 108 sÀ 1 is also significant larger than that of POTBC
(0.10 � 108 sÀ 1). Compared to POTBC, the presence of -OPhC(CH3)3
substituent in POTBC(β-OPB)4 does not cause the intra-molecular fluo-
rescence quenching indicated by larger kf, Φf and τf values than POTBC.
Although -OPhC(CH3)3 is an electron donor, no intra-molecular photo-
induced electron (or energy) transfer occurs from -OPhC(CH3)3 to
POTBC unit. These values indicate that POTBC(β-OPB)4 is a better
fluorescence emitter. Since kf of POTBC(β-OPB)4 is larger than that of
POTBC, its Φf is larger, since Φf ¼ kf⋅τf. H2Pc(β-OPB)4 exhibits lower
values in Φf than POTBC(β-OPB)4, since it is an acid and shows proton
dissociation from S1 state which effectively competes with fluorescence.
photolysis technique. The transient absorption spectra are shown in
Fig. 5. In nitrogen-saturated THF, the time resolved spectra show posi-
tive absorption band with the peak maximum at 465 nm, the spectra are
well consistent with the typical T1-Tn transient absorption of other
POTBCs in literature [16,17]. The negative absorption bands match the
UV–Vis absorption of the ground state (S0) of POTBC(β-OPB)4. With the
decrease of the positive band, the negative absorption rises concomi-
tantly with an isosbestic point, indicating that the decay of T1 re-
generates S0 (T1→S0). The T1 decay at 465 nm (Fig. 5) is
monoexponential and the calculated lifetime is 455
μ
s in N2-saturated
THF, this very long T1 lifetime makes it good singlet oxygen photosen-
sitizer. In air-saturated THF, the triplet lifetime is shortened to 0.31
μ
s,
indicating a very strong oxygen quenching, due to the efficient energy
1
transfer process: T1 þ O2 → S0 þ O2. The oxygen quenching rate con-
stant is then computed to be 1.61 � 109 MÀ 1sÀ 1, suggesting the
quenching is diffusion controlled. These facts suggest that T1 is indeed
formed upon the photo excitation of POTBC(β-OPB)4.
3.4. Singlet oxygen
Singlet oxygen, O2(1Δg) or 1O2, is the lowest excited singlet state of
molecular oxygen (O2), it is a highly reactive oxygen species that is
mainly responsible for killing cancer cells in photodynamic therapy. O2
(1Δg) is formed by energy transfer from T1 of a photosensitizer to mo-
lecular oxygen (T1þO2 → S0þ1O2). The most striking properties of 1O2
are its NIR photoluminescence at 1270 nm and immediate quantitative
reaction with 1,3-diphenylisobenzofuran (DPBF).
3.3. Excited triplet state formation
We then measured the transient absorption spectra of POTBC
Fig. 6 displays the NIR emission from POTBC(β-OPB)4 in air-
saturated solvent (CHCl3 and CCl4) with excitation at 655 nm. The
(β-OPB)4 with laser excitation at 655 nm using nanosecond laser flash
Fig. 6. NIR emission from singlet oxygen using our compounds as photosensitizer (10 μM) in air saturated solution with excitation at 655 nm.
4

X. Lu and X.-F. Zhang
Dyes and Pigments 179 (2020) 108421
Fig. 7. Left: time resolved DPBF (20
μ
M) absorption decrease due to singlet oxygen oxidation using our compounds as photosensitizer (5
μM) in air saturated
solution with LED light irradiation at 660 nm. Right: plot of the absorbance of DPBF (20
μ
M) containing photosensitizer (5 M) in air saturated solution with LED
μ
light irradiation at 660 nm, the zero order kinetics of DPBF concentration change with time.
NIR emission was observed only in the co-presence of the three factors
(photosensitizer, oxygen, and light excitation). The peak maxima (1275
nm) and band shape are all consistent with the emission spectra of
The absorption decrease of DPBF does not occur when the light irradi-
ation or the oxygen is absent.
The absorption decrease of DPBF is linearly dependent on the irra-
diation time (Fig. 7), from which the formation quantum yield of singlet
oxygen (ΦΔ) is obtained (Table 1) using zinc phthalocyanine as the
reference compound. ΦΔ of POTBC(β-OPB)4 is 0.40 � 0.01 which is very
close to that of POTBC, but it is remarkably higher than that of H2Pc
(β-OPB)4 (ΦΔ ¼ 0.13), indicating that they are reasonably good singlet
oxygen photosensitizer. H2Pc(β-OPB)4 exhibits lower values in ΦΔ than
POTBC(β-OPB)4, since it is an acid and shows proton dissociation from
S1 state which effectively competes with fluorescence and T1 formation.
O2(1Δg) [19]. The emission decay lifetime at 1275 nm is 213
μs, which is
also very close to the reported value of singlet oxygen (1Δg) [19]. In
nitrogen-saturated CHCl3 and CCl4, however, the emission spectra of
1275 nm were not observed. All these facts indicate that POTBC(β-OPB)4
and H2Pc(β-OPB)4 photosensitize the production of singlet oxygen (1Δg).
Fig. 7 shows the oxidation of DPBF using POTBC(β-OPB)4 and H2Pc
(β-OPB)4 as photosensitizer in air-saturated THF with photo excitation at
660 nm. The absorption of DPBF is decreased with irradiation time while
the absorption of POTBC(β-OPB)4 and H2Pc(β-OPB)4 show no change.
Fig. 8. The solar cell device architect (left) and SEM image.
5

X. Lu and X.-F. Zhang
Dyes and Pigments 179 (2020) 108421
Fig. 9. Left: JÀ V characteristics of perovskite solar cell devices using H2Pc(β-OPB)4 and POTBC(β-OPB)4 as HTM respectively. Right: incident photon-to-current
conversion efficiency (EQE) spectra of perovskite solar cells assembled with H2Pc(β-OPB)4 and POTBC(β-OPB)4 as HTM respectively. The solar cells were
measured under standard one sun conditions.
Voc is 0.94 V, and the fill factor (FF) is 71%, leading to a higher PCE of
Table 2
15.8% with good stability (Fig. S7 in supporting information). Forward
Photovoltaic parametersa.
scanning shows slightly better performance (Fig. S8 in supporting in-
Undoped HTL
Jsc (mA/cm2)
Voc(V)
Fill Factor (%)
Efficiency (%)
formation). It is clear that POTBC(β-OPB)4 shows remarkable better
performance than undoped spiro-OMeTAD.
H2Pc(β-OPB)4
POTBC(β-OPB)4
Spiro-OMETAD
22.5
23.7
17.8
1.07
0.94
0.97
64.80
70.97
59.00
15.6
15.8
10.8
The high Jsc of the solar cell devices is supported by the EQE spectra
depicted in Fig. 9. For both H2Pc(β-OPB)4 and POTBC(β-OPB)4, the EQE
spectra and Jsc curves show that the effective light absorbing region is
300–800 nm for the perovskite solar cells. For POTBC(β-OPB)4, how-
ever, the EQE values are lying above that of H2Pc(β-OPB)4 in 300–800
nm, so that POTBC(β-OPB)4 absorbs more light and has larger Jsc. The
integrated Jsc values from this plot are consistent with that obtained
from J-V curves. The fill factor of POTBC(β-OPB)4 is also significantly
greater, therefore the power conversion efficiency of POTBC(β-OPB)4 is
higher than that of H2Pc(β-OPB)4 although its Voc is smaller.
a
scan rate is 0.05 V/s, photovoltaic parameters were averaged over 9 devices.
3.5. Solar cell performance as undoped hole transporting material
Metal halide perovskite solar cells (PSC) are attracting high research
interest currently due to its excellent power conversion efficiency (PCE)
over 20%, easy fabrication and low cost [20–22]. Hole transporting
layer (HTL) plays the key role in highly efficient metal halide PSC.
Doped Spiro-OMeTAD is usually the HTL for such PSCs, since
Spiro-OMeTAD is low conductive such that undoped Spiro-OMeTAD as
HTL is not efficient. However, Spiro-OMeTAD is very expensive and the
lithium salt doping causes the remarkable instability of the PSCs,
therefore undoped hole transporting materials are highly desirable.
Phthalocyanines have been recently applied as HTL of PSC and show
good performance [23–26]. Hereby we examine if POTBC(β-OPB)4 and
its phthalocyanine precursor can be good candidate as effective hole
transporting materials.
4. Conclusion
We have synthesized POTBC(β-OPB)4 from its H2Pc(β-OPB)4 pre-
cursor. POTBC(β-OPB)4 shows good red fluorescence properties and
excited triplet state formation capability. POTBC(β-OPB)4 effectively
photosensitizes the formation of singlet oxygen. When POTBC(β-OPB)4
is used as HTM of PSC, PCE reaches 15.8%. These facts suggest that
POTBC(β-OPB)4 is a promising fluorescence imaging agent and singlet
oxygen photosensitizer for photodynamic therapy of tumor. It is also a
good candidate as HTL of undoped PSC.
We determined the hole mobility using a device structure glass/ITO
(~300 nm)/organic layer (~200 nm)/Au(~50 nm) at room tempera-
ture. The value of the hole mobility for POTBC(β-OPB)4 is 1.23 � 10À 3
cm2/(V s), which is much larger than 1.0 � 10À 4 cm2/(V s) of undoped
spiro-OMeTAD, and in the same order as that of LiTFSI doped spiro-
OMeTAD. This indicates it is a good hole transporting material and
can act as good dopant free HTMs.
Declaration of competing interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
The solar cell device architect is shown in Fig. 8. The solar cell de-
vices are fabricated by spin coating method except the Au layer which is
deposited by vacuum thermal vaporization. The JÀ V (current densi-
tyÀ voltage) curves are displayed in Fig. 9. The J-V of the perovskite
solar cells were measured under the same conditions using standard
solar power simulator with 100 mW/cm2 photon flux (AM 1.5G). The
corresponding photovoltaic parameters were averaged over nine devices
(Table 2). In the case of undoped Spiro-OMeTAD as HTM, the short-
circuit current density (Jsc) is 17.8 mA cmÀ 2, open circuit voltage
(Voc) is 0.97 V, the fill factor (FF) is 59.0%, giving a low PCE of 10.80%,
this is due to the low hole mobility and low electrical conductivity of the
undoped spiro-OMeTAD layer. For H2Pc(β-OPB)4, however, Jsc is 22.5
mA cmÀ 2, Voc is 1.07 V, and the fill factor (FF) is 64.8%, leading to a PCE
of 15.6%. For the optimized cell device of POTBC(β-OPB)4, Jsc is 23.7
mA cmÀ 2 with stable power output (Fig. S6 in supporting information),
CRediT authorship contribution statement
Xulin Lu: Investigation. Xian-Fu Zhang: Conceptualization, Super-
vision, Funding acquisition, Writing - original draft.
Acknowledgements
We thank the financial support from Hebei Provincial Hundred
Talents Plan (Contract E2013100005).
Appendix A. Supplementary data
Supplementary data related to this article can be found at https
6

X. Lu and X.-F. Zhang
Dyes and Pigments 179 (2020) 108421
[15] Lu G, Li J, Yan S, He C, Shi M, Zhu W, et al. Self-assembled organic nanostructures
and nonlinear optical properties of heteroleptic corrole-phthalocyanine europium
triple-decker complexes. Dyes Pigments 2015;121:38–45.
://doi.org/10.1016/j.dyepig.2020.108421.
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