Abstract
We synthesized a series of Ru(II) metal complexes TFRS-1, -2, -4, -21, -22 and -24 with a single 4,4′-dicarboxylic acid-2,2′-bipyridine together with two functionalized pyridyl azolate ancillary ligands consisting of pyrazolate or triazolate groups. Both photophysical measurements and DFT/TDDFT calculations were conducted to gain insight into their electronic and optical properties. The triazolate series of sensitizers TFRS-21, -22 and -24 showed an enlarged optical band gap with respect to their pyrazolate counterparts TFRS-1, -2 and -4. When employed in dye sensitized solar cells (DSCs), the triazolate sensitizers show slightly inferior JSC values due to the poor incident photon-to-current conversion efficiencies recorded compared to the pyrazolate series. Moreover, the endowed 5-(hexylthio)thiophen-2-yl substituents exert a notable hyperchromic effect and bathochromic shift in the absorption spectra, which then improves the short circuit current JSC to 18.7 and 15.5 mA cm−2 and the overall conversion efficiency to η = 10.2% and 8.25% for TFRS-4 and TFRS-24, respectively. For the evaluation of VOC, transient photocurrent and photovoltage decay measurements were carried out to compare the rates of interfacial recombination of electrons from the TiO2 conduction band to electrolyte.
Highlights
As the situation of global warming continues, it is becoming obvious that mankind must switch to renewable energies, which encourages our societies to place strong emphasis on the development of emerging photovoltaic technologies
The thiocyanate ligands incorporated in typical Ru(II) sensitizers are believed to provide the weakest bonding of the whole molecule, making the sensitizers and, the as-fabricated solar cells somewhat unstable under excessive thermal stress and/or light soaking.[16]
The sensitizer TFRS-4, featuring a hexylthiothiophene appendage on pyrazolate chelates, shows a distinctive red-shi ed metalto-ligand charge transfer bands (MLCT) absorption, which improves the light-capturing ability in the visible and near infrared regions resulting in the best overall conversion efficiency (h 1⁄4 10.2%) among all sensitizers studied
Summary
As the situation of global warming continues, it is becoming obvious that mankind must switch to renewable energies, which encourages our societies to place strong emphasis on the development of emerging photovoltaic technologies. To gain insight into the electronic and optical properties of the investigated series of sensitizers, we performed DFT/TDDFT calculations in DMF solution on both the pyrazolate series TFRS-1, -2 and -4 and the triazolate series TFRS-21, -22 and -24, considering for all systems a number of protons carried by the carboxylic acid anchoring groups of the 4,40-bipyridine ranging from 0 to 2.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
