A novel hyperbranched zinc phthalocyanine dye, i.e. HBZnPc-COOH, was synthesized, characterized, and applied into
dye-sensitized solar cells (DSSCs) as TiO2 sensitizer. UV-visible absorption, steady-state fluorescence, femtosecond
time-resolved fluorescence, cyclic voltammetry, current–voltage characteristics, and photoelectrical properties of the
active material/device were investigated. The utilization of hyperbranched structure was proved to be able to solve the
aggregation issue of phthalocyanine dyes on TiO2 surface which has been widely considered as one of the key limiting
issues that severely lower the efficiencies of phthalocyanine dye sensitized solar cells. With appropriate highest occupied
molecular orbital and lowest unoccupied molecular orbital energy levels, HBZnPc-COOH exhibited efficient and
ultrafast multi-phasic electron injection from both the Soret band and Q band to the conduction band of TiO2, leading to
a solar cell power conversion efficiency of 1.15% and a high incident photon to current conversion efficiency of 66.7%
at 670 nm.
Third-order nonlinear optical properties of three isomeric tetrapyrrole triads, i.e. mixed (porphyrinato)(phthalocyaninato)
yttrium double-decker complexes appended with one metal free porphyrin chromophore at the para, meta, and orthoposition, respectively, of one meso-phenyl group of the porphyrin ligand in the double-decker unit through ester linkage,
3-5, were comparatively investigated along with the model compounds metal free meso-tetrakis(4-tert-butylphenyl)
porphyrin H2TBPP (1) and mixed [meso-tetrakis(4-tert-butylphenyl)porphyrinato]
[1,4,8,11,15,18,22,25-octakis(butyloxyl)phthalocyaninato] yttrium double-decker complex YIIIH(TBPP)
[Pc(α-OC4H9)8] (2) by using
Z-scan technique with the fundamental (800 nm) laser emission from a Ti:sapphire femtosecond laser system. Strong reverse
saturable absorption (RSA) properties of complexes 2-5 were observed. Interestingly, under highly intense irradiation, an
RSA-SA-RSA-SA-RSA switch behavior was evolved in the tight focal intensity regime on the Z-scan profiles of
complexes 3-5. Under the laser irradiation with focal intensity of 7.48-8.39 GW.cm-2, the triads 3 and 4 with the metal
free porphyrin chromophore appended at the para or meta positions of the meso-phenyl group of the porphyrin ligand in
the double-decker unit retained a characteristic response of RSA. In contrast, the triad 5 with the metal free porphyrin
chromophore appended at the ortho position has already shown a trend of SA peaks at the same intensity range,
revealing the effect of the position of porphyrin-substituent on the nonlinear optical properties of the triads.
Nonlinear optical properties of a series of protonated mixed (porphyrinato)(phthalocyaninato) rare-earth double-decker
complexes [MIIIH(TClPP){Pc(α-OC4H9)8}] (1-6;
M = Sm, Eu, Tb, Y, Ho, Lu; TClPP = meso-tetrakis
(4-chlorophenyl)porphyrinate; Pc(α-OC4H9)8 =
1,4,8,11,15,18,22,25-octakis(1-butyloxy)phthalocyaninate) in
dichloromethane were studied by using Z-scan technique with the fundamental laser emission at 800 nm from a
Ti:sapphire femtosecond laser system under different incident laser intensities. All these complexes showed strong
reverse saturable absorption related to the excited singlet population in a simple three-energy-level model which was
established for the interpretation of the experimental results. Both the linear and effective nonlinear absorption
coefficients of these complexes decreased approximately following the ionic radius contraction sequence of the rareearth(
III) cations within these complexes under the same situations. The effective excited-state absorption cross sections
were determined as well.
Cu2ZnSnS4 (CZTS) was obtained from a sol-gel precursor which consists of copper chloride, zinc chloride, tin chloride, and thiourea. CZTS thin films were prepared by spin-coating the sol-gel precursor followed by annealing in a nitrogen atmosphere. The morphology, composition, and structure of the absorber layer were studied by scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction, and Raman scattering. The optical measurement shows the bandgap of these films is ∼1.51 eV, and the optical absorption coefficient is on the order of 104 cm−1. CZTS solar cells with a structure of low-alkali glass/Mo/CZTS/CdS/i-ZnO/ZnO:Al/Al grid were tentatively fabricated. The best solar cell showed a short-circuit current density of 5.06 mA/cm2, an open-circuit voltage of 358 mV, a fill factor of 34.66%, and an efficiency of 0.63% under AM1.5 (100 mW/cm2) illumination. These results demonstrate the CZTS thin films were successfully deposited by a cheap sol-gel technique.
KEYWORDS: Solar cells, Absorption, Luminescence, Scanning electron microscopy, Energy efficiency, Dye sensitized solar cells, Carbon, Resistance, Picosecond phenomena, Organic semiconductors
Organic-inorganic hybrid solar cells with a cell structure of indium tin oxide/TiO2/TiOx:hyperbranched phthalocyanine/CuSCN/Au (or carbon) have been fabricated by solution based processing using three hyperbranched phthalocyanines (H2PPc, TiOPPc and CuPPc) as light-absorbing materials. These organic-inorganic hybrid solar cells are extremely thin absorber solar cells, which possess p-i-n heterojunctions ("i," an intrinsic absorber layer), as they were confirmed by scanning electron microscopy. With an illuminated area of 1 cm2, a solar cell made from H2PPc achieved conversion efficiency of 0.23% under 1-sun air mass 1.5 global illumination. The lower conversion efficiency for the cell made from CuPPc was likely due to the energy loss in the formation of triplet states with an intersystem crossing time of 0.76 ps.
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