New Paradigm in Molecular Engineering of Sensitizers for Solar Cell Applications

Abstract

A novel thiocyanate-free cyclometalleted ruthenium sensitizer for solar cells is designed and developed. Upon anchoring to nanocrystalline TiO(2) films, it exhibits a remarkable incident monochromatic photon-to-current conversion efficiency of 83%. The solar cell employing a liquid-based electrolyte exhibits a short circuit photocurrent density of 17 mA/cm(2), an open circuit voltage of 800 mV, and a fill factor of 0.74, corresponding to an overall conversion efficiency of 10.1% at standard AM 1.5 sunlight. To understand the structural, electronic, and optical properties of the cyclometalleted ruthenium sensitizer, we have investigated using density functional theory (DFT) and time-dependent DFT (TDDFT). Our results show the HOMO is located mostly on ruthenium and cyclometalated ligand, while the LUMO is on 4-carboxylic acid-4'-carboxylate-2,2'-bipyridine. Molecular orbitals analysis confirmed the experimental assignment of redox potentials, and TDDFT calculations allowed assignment of the visible absorption bands. The present findings provide new design criteria for the next generation of ruthenium sensitizers and help foster widespread interest in the engineering of new sensitizers that interact effectively with the I(-)/I(3)(-) redox couple.

Examining architectures of photoanode–photovoltaic tandem cells for solar water splitting

“…A squaraine dye coded as SQ1 13 and the black dye (N749) 11 were chosen based on their complementary properties over their absorption spectra. The electrolyte A6141 14 was selected for its electrochemical properties allowing a high current density with low concentration and therefore high light transmission. The N749 dye and A6141 electrolyte were synthesized in our labs, and the SQ1 dye is the courtesy of Pr.…”

Organometallic Materials for Electroluminescent and Photovoltaic Devices

“…However, no obvious bathochromic shift of the absorption spectrum was observed. Grätzel and coworkers developed a novel thiocyanate-free cyclometalleted ruthenium sensitizer (Ru-F, Scheme 3) with electron acceptor fluorine atoms substituted on one ligand (Bessho et al 2009). Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations show that the HOMO is located mostly on ruthenium and the cyclometalated ligands.…”

Sticking and patching: tuning and anchoring cyclometallated ruthenium(ii) complexes

“…In 2009, Grätzel and coworkers reported a 10.1% global efficiency for a DSC containing [Ru(dcbpy) 2 (F 2 ppy)] + (dcbpy = 2,2'-bipyridine-4,4'-dicarboxylic acid, H(F 2 ppy) = 2-(2,4-difluorophenyl)pyridine). 7 Replacing thiocyanate by an anionic C^N ligand provides a means of tuning the HOMO-LUMO properties of the dyes. The HOMO of a [Ru(N^N) 2 (C^N)] + complex is localized on the metal and C^N ligand, 8 and therefore the energy of the HOMO can be altered by introducing electron-withdrawing or electrondonating substituents into the phenyl ring.…”