5 research outputs found
Tuning the HOMO and LUMO Energy Levels of Organic Dyes with <i>N</i>‑Carboxomethylpyridinium as Acceptor To Optimize the Efficiency of Dye-Sensitized Solar Cells
Different
from traditional D−π–A sensitizers
(the traditional design concept of the organic dyes is the donor−π-linker–acceptor
structure), a series of organic dyes with pyridinium as acceptor have
been synthesized in order to approach the optimal energy level composition
in the TiO<sub>2</sub>–dye–iodide/triiodide system in
the dye-sensitized solar cells. HOMO and LUMO energy level tuning
is achieved by varying the conjugation units and the donating ability
of the donor part. Detailed investigation on the relationship between
the dye structure and photophysical, photoelectrochemical properties
and performance of DSSCs is described. For TPA-based dyes, by substituting
the 3-hexylthiophene group with a carbon–carbon double bond
as π-spacer, the bathochromic shift of absorption spectra and
higher current density (<i>J</i><sub><i>sc</i></sub>) are achieved. When the methoxyl and <i>n</i>-hexoxyl
are introduced into <b>CM301</b> to construct dyes <b>CM302</b> and <b>CM303</b>, the absorption peak is red-shifted compared
with that of <b>CM301</b> due to the increase of the electron-donating
ability. The devices fabricated with sensitizers <b>CM302</b> and <b>CM303</b> show higher <i>J</i><sub><i>sc</i></sub> and open-circuit voltage (<i>V</i><sub><i>oc</i></sub>) than those of the device sensitized by <b>CM301</b>, which can be mainly attributed to the wider incident
photon-to-current conversion efficiency (IPCE) response and the suppression
of electron recombination between TiO<sub>2</sub> film and electrolyte,
respectively. The effects of different electron donors in DSSCs application
are compared, and the results show that sensitizers with a phenothiazine
(PTZ) electron-donating unit give a promising efficiency, which is
even better than the TPA-based dyes. This is because the PTZ unit
displayed a stronger electron-donating ability than the TPA unit (oxidation
potential of 0.82 and 1.08 V vs the normal hydrogen electrode (NHE),
respectively). For sensitizers <b>CM306</b> and <b>CM307</b>, the introduction of 1,3- bisÂ(hexyloxy)Âphenyl increases the donating
ability of the donor part. Furthermore, the presence of long alkyl
chains decreases the dye adsorption amount on the TiO<sub>2</sub> surface,
which diminishes dye aggregation and the electron recombination effectively,
though, with less adsorption amount of dyes on TiO<sub>2</sub>, the
device sensitized by dye <b>CM307</b> obtained the best conversion
efficiency of 7.1% (<i>J</i><sub><i>sc</i></sub> = 13.6 mA·cm<sup>–2</sup>, <i>V</i><sub><i>oc</i></sub> = 710 mV, <i>FF</i> = 73.6%) under AM
1.5G irradiation (100 mW·cm<sup>–2</sup>)
Efficient Panchromatic Organic Sensitizers with Dihydrothiazole Derivative as π‑Bridge for Dye-Sensitized Solar Cells
Novel
organic dyes <b>CC201</b> and <b>CC202</b> with dihydrothiazole
derivative as π-bridge have been synthesizedand applied in the
DSSCs. With the synergy electron-withdrawing of dihydrothiazole and
cyanoacrylic acid, these two novel dyes <b>CC201</b> and <b>CC202</b> show excellent response in the region of 500–800
nm. An efficiency as high as 6.1% was obtained for the device fabricated
by sensitizer <b>CC202</b> together with cobalt electrolyte
under standard light illumination (AM 1.5G, 100 mW cm<sup>–2</sup>). These two novel D-π-A panchromatic organic dyes gave relatively
high efficiencies except common reported squaraine dyes
Structure Engineering of Hole–Conductor Free Perovskite-Based Solar Cells with Low-Temperature-Processed Commercial Carbon Paste As Cathode
Low-temperature-processed (100 °C)
carbon paste was developed as counter electrode material in hole–conductor
free perovskite/TiO<sub>2</sub> heterojunction solar cells to substitute
noble metallic materials. Under optimized conditions, an impressive
PCE value of 8.31% has been achieved with this carbon counter electrode
fabricated by doctor-blading technique. Electrochemical impedance
spectroscopy demonstrates good charge transport characteristics of
low-temperature-processed carbon counter electrode. Moreover, this
carbon counter electrode-based perovskite solar cell exhibits good
stability over 800 h
Novel Small Molecular Materials Based on Phenoxazine Core Unit for Efficient Bulk Heterojunction Organic Solar Cells and Perovskite Solar Cells
Two novel Acceptor-Donor-Acceptor
(A-D-A) structured small molecular
(SM-) materials <b>POZ2</b> and <b>POZ3</b> using an electron-rich
phenoxazine (POZ) unit as a core building block were designed and
synthesized. Their unique characteristics, such as suitable energy
levels, strong optical absorption in the visible region, high hole
mobility, and high conductivity, prompted us to use them both as p-type
donor materials (DMs) in SM-bulk heterojunction organic solar cells
(BHJ OSCs) and as hole transport materials (HTMs) in CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub>-based perovskite solar cells (PSCs).
The <b>POZ2</b>-based devices yielded promising power conversion
efficiencies (PCEs) of 7.44% and 12.8% in BHJ OSCs and PSCs, respectively,
which were higher than the PCEs of 6.73% (BHJ-OSCs) and 11.5% (PSCs)
obtained with the <b>POZ3</b>-based devices. Moreover, our results
demonstrated that the <b>POZ2</b> employing the electron-deficient
benzothiazole (BTZ) as linker exhibited higher hole mobility and conductivity
than that of the <b>POZ3</b> using thiophene as linker, leading
to better device performance both in BHJ-OSCs and PSCs. These results
also provide guidance for the molecular design of high charge carrier
mobility SM-materials for highly efficient BHJ OSCs and PSCs in the
future
Highly Efficient Integrated Perovskite Solar Cells Containing a Small Molecule-PC<sub>70</sub>BM Bulk Heterojunction Layer with an Extended Photovoltaic Response Up to 900 nm
We
demonstrate a high efficiency perovskite solar cell (PSC) integrated
with a bulk heterojunction layer, based on acceptor–donor–acceptor
(A–D–A) type hole transport material (HTM) and PC<sub>70</sub>BM composite, yielding improved photoresponse. Two A–D–A-structured
hole transporting materials termed <b>M3</b> and <b>M4</b> were designed and synthesized. Applied as HTMs in PSCs, power conversion
efficiencies (PCEs) of 14.8% and 12.3% were obtained with <b>M3</b> and <b>M4</b>, respectively. The HTMs <b>M3</b> and <b>M4</b> show competitive absorption, but do not contribute to photocurrent,
resulting in low current density. This issue was solved by mixing
the HTMs with PC<sub>70</sub>BM to form a bulk heterojunction (BHJ)
layer and integrating this layer into the PSC as hole transport layer
(HTL). Through careful interface optimization, the (FAPbI<sub>3</sub>)<sub>0.85</sub>Â(MAPbBr<sub>3</sub>)<sub>0.15</sub>/HTM:PC<sub>70</sub>BM integrated devices showed improved efficiencies of 16.2%
and 15.0%, respectively. More importantly, the incident-photon-to-current
conversion efficiency (IPCE) spectrum shows that the photoresponse
is extended to 900 nm by integrating the <b>M4</b>:PC<sub>70</sub>BM based BHJ and (FAPbI<sub>3</sub>)<sub>0.85</sub>Â(MAPbBr<sub>3</sub>)<sub>0.15</sub> layers