2 research outputs found
Benzimidazole-Branched Isomeric Dyes: Effect of Molecular Constitution on Photophysical, Electrochemical, and Photovoltaic Properties
Three
benzimidazole-based isomeric organic dyes possessing two triphenylamine
donors and a cyanoacrylic acid acceptor are prepared by stoichiometrically
controlled Stille or Suzuki–Miyaura coupling reaction which
predominantly occurs on the <i>N</i>-butyl side of benzimidazole
due to electronic preferences. Combined with the steric effect of
the <i>N</i>-butyl substituent, placement of the acceptor
segment at various nuclear positions of benzimidazole such as C2,
C4, and C7 led to remarkable variations in intramolecular charge transfer
absorption, electron injection efficiency, and charge recombination
kinetics. The substitution of acceptor on the C4 led to red-shifted
absorption, while that on C7 retarded the charge transfer due to twisting
in the structure caused by the butyl group. Because of the cross-conjugation
nature and poor electronic interaction between the donor and acceptor,
the dye containing triphenylamine units on C4 and C7 and the acceptor
unit on C2 showed the low oxidation potential. Thus, this dye possesses
favorable HOMO and LUMO energy levels to render efficient sensitizing
action in solar cells. Consequently, it results in high power conversion
efficiency (5.01%) in the series with high photocurrent density and
open circuit voltage. The high photocurrent generation by this dye
is reasoned to it exceptional charge collection efficiency as determined
from the electron impedance spectroscopy
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