5 research outputs found
Unsymmetrical Squaraines Incorporating Quinoline for Near Infrared Responsive Dye-Sensitized Solar Cells
Two new unsymmetrical squaraines (<b>WCH-SQ10</b> and <b>WCH-SQ11</b>), wherein the electron-rich 3,4-ethylenedioxy-thiophene conjugated fragment was linked unconventionally to the squaraine core and triphenyl amine donor, and carboxylic acid substituted quinoline was used as an acceptor, were prepared. <b>WCH-SQ10</b> and <b>WCH-SQ11</b> dyes in ethanol have the λ<sub>max</sub> of 686 and 673 nm, respectively. The corresponding photovoltaic devices exhibit an attractively panchromatic response over 1000 nm, suggesting that quinoline benefits the low energetic electron injection
Diastereoisomers of Ruthenium Dyes with Unsymmetric Ligands for DSC: Fundamental Chemistry and Photovoltaic Performance
A new
thiocyanic acid-free ruthenium sensitizer, CYC-B29, containing
two unsymmetrical ancillary ligands, was synthesized, and its three
diastereoisomers CYC-B29-CC, CYC-B29-TT, and CYC-B29-CT with significantly
different optical, electronic, and electrochemical properties were
carefully separated. CYC-B29-TT with the smallest size has the strongest
absorption coefficient of the MLCT band, the shortest λ<sub>max</sub>, the lowest highest occupied molecular orbital level and
the highest dye loading. Therefore, dye-sensitized solar cell based
on CYC-B29-TT has the highest efficiency, which is two times higher
than that of CYC-B29-CC-sensitized device and 10% higher than that
of N719-based cell. Time-dependent density functional theory-calculated
transition bands for the three isomers are not identical, and only
CYC-B29-TT has the calculated transition bands close to the experimental
absorption profile. Although the calculated transition
bands for CYC-B29-CC and CYC-B29-CT are not consistent with the experimental
data, the ground-state vertical excitation energy with oscillator
strength and electron-density difference map data combining with the
dye loading predict correctly the order of the photocurrent for the
three isomers sensitized devices
<i>S</i>,<i>N</i>‑Heteroacene-Based Copolymers for Highly Efficient Organic Field Effect Transistors and Organic Solar Cells: Critical Impact of Aromatic Subunits in the Ladder π‑System
Three novel donor–acceptor
alternating polymers containing ladder-type pentacyclic heteroacenes
(<b>PBo</b>, <b>PBi</b>, and <b>PT</b>) are synthesized,
characterized, and further applied to organic field effect transistors
(OFETs) and polymer solar cells. Significant aspects of quinoidal
characters, electrochemical properties, optical absorption, frontier
orbitals, backbone coplanarity, molecular orientation, charge carrier
mobilities, morphology discrepancies, and the corresponding device
performances are notably different with various heteroarenes. <b>PT</b> exhibits a stronger quinoidal mesomeric structure, linear
and coplanar conformation, smooth surface morphology, and better bimodal
crystalline structures, which is beneficial to extend the π-conjugation
and promotes charge transport via 3-D transport pathways and in consequence
improves overall device performances. Organic photovoltaics based
on the <b>PT</b> polymer achieve a power conversion efficiency
of 6.04% along with a high short-circuit current density (<i>J</i><sub>SC</sub>) of 14.68 mA cm<sup>–2</sup>, and
a high hole mobility of 0.1 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> is fulfilled in an OFET, which is superior to those
of its counterparts, <b>PBi</b> and <b>PBo</b>
Metal-Free Tetrathienoacene Sensitizers for High-Performance Dye-Sensitized Solar Cells
A new series of metal-free organic
chromophores (TPA-TTAR-A (<b>1</b>), TPA-T-TTAR-A (<b>2</b>), TPA-TTAR-T-A (<b>3</b>), and TPA-T-TTAR-T-A (<b>4</b>)) are synthesized for application
in dye-sensitized solar cells (DSSC) based on a donor-Ï€-bridge-acceptor
(D−π–A) design. Here a simple triphenylamine (TPA)
moiety serves as the electron donor, a cyanoacrylic acid as the electron
acceptor and anchoring group, and a novel tetrathienoacene (TTA) as
the π-bridge unit. Because of the extensively conjugated TTA
π-bridge, these dyes exhibit high extinction coefficients (4.5–5.2
× 10<sup>4</sup> M<sup>–1</sup> cm<sup>–1</sup>). By strategically inserting a thiophene spacer on the donor or
acceptor side of the molecules, the electronic structures of these
TTA-based dyes can be readily tuned. Furthermore, addition of a thiophene
spacer has a significant influence on the dye orientation and self-assembly
modality on TiO<sub>2</sub> surfaces. The insertion of a thiophene
between the π-bridge and the cyanoacrylic acid anchoring group
in TPA-TTAR-T-A (dye <b>3</b>) promotes more vertical dye orientation
and denser packing on TiO<sub>2</sub> (molecular footprint = 79 Ã…<sup>2</sup>), thus enabling optimal dye loading. Using dye <b>3</b>, a DSSC power conversion efficiency (PCE) of 10.1% with <i>V</i><sub>oc</sub> = 0.833 V, <i>J</i><sub>sc</sub> = 16.5 mA/cm<sup>2</sup>, and FF = 70.0% is achieved, among the
highest reported to date for metal-free organic DSSC sensitizers using
an I<sup>–</sup>/I<sub>3</sub><sup>–</sup> redox shuttle.
Photophysical measurements on dye-grafted TiO<sub>2</sub> films reveal
that the additional thiophene unit in dye <b>3</b> enhances
the electron injection efficiency, in agreement with the high quantum
efficiency
Performance Characterization of Dye-Sensitized Photovoltaics under Indoor Lighting
Indoor
utilization of emerging photovoltaics is promising; however,
efficiency characterization under room lighting is challenging. We
report the first round-robin interlaboratory study of performance
measurement for dye-sensitized photovoltaics (cells and mini-modules)
and one silicon solar cell under a fluorescent dim light. Among 15
research groups, the relative deviation in power conversion efficiency
(PCE) of the samples reaches an unprecedented 152%. On the basis of
the comprehensive results, the gap between photometry and radiometry
measurements and the response of devices to the dim illumination are
identified as critical obstacles to the correct PCE. Therefore, we
use an illuminometer as a prime standard with a spectroradiometer
to quantify the intensity of indoor lighting and adopt the reverse-biased
current–voltage (<i>I</i>–<i>V</i>) characteristics as an indicator to qualify the <i>I</i>–<i>V</i> sampling time for dye-sensitized photovoltaics.
The recommendations can brighten the prospects of emerging photovoltaics
for indoor applications