Adapting Ruthenium Sensitizers to Cobalt Electrolyte Systems

Abstract

In this work, we report the use of bulky substitutions in a new heteroleptic ruthenium(II) bipyridine complex, Ru(NCS)2LL', coded TT-230 to obtain high open-circuit potential in a dye-sensitized solar cell (where L is a bipyridine ligand appended with two cyclopenta(2,1-b;3,4-bA)dithiophene moieties, and L' = 4,4,'-dicarboxylic acid 2,2'-bipyridine). The electrolytes based on cobalt complexes have shown significant advantages in terms of attainable open-circuit potential compared to the standard iodide/tri-iodide redox mediators. These merits of the cobalt complexes were previously realized with a porphyrin sensitizer, achieving a VOC greater than 1 V in DSC. However, with conventional Ru(II)-polypyridyl complexes such as the C101 dye, similar increase in the VOC could not be attained due to the enhanced recombination. In this work, we have shown that the use of bulky substituents can prevent the back reaction of photogenerated electron and subsequently increase the open-circuit potential of the device. The recombination processes were investigated by transient photovoltage decay measurements.

Synthesis of Amphiphilic RuII Heteroleptic Complexes Based on Benzo[1,2‐b:4,5‐b′]dithiophene: Relevance of the Half‐Sandwich Complex Intermediate and Solvent Compatibility

“…When using the cobalt‐based electrolyte, an impressive 92 mV improvement in the V OC was observed for the TT222 +CHENO device in comparison with the iodine‐based electrolyte A. However, as reported in other cases for Ru II heteroleptic complex dyes,52 the J SC concurrently dropped drastically to 4.7 mA cm −2 , resulting in a lower overall PCE of 2.7 %. Next, we focused on the optimization of LiI concentration for the iodine‐based electrolyte.…”

Rational Design of High-Efficiency Organic Dyes in Dye-Sensitized Solar Cells by Multiscale Simulations

“…However, the measured V OC rarely reaches half of the maximum theoretical attainable values. The main reason for the drop in V OC comes from the charge recombination in the TiO 2 film, which determines the final Fermi level position . However, V OC has attracted even less attention in previous literature. , In other words, it is simply equal to the energy difference between the LUMO of the dye and the CB of TiO 2 .…”

Designing All‐Inorganic EuO‐Sensitized TiO2 Solar Cell from 4f‐3d Composite Bandgap Structure

“…Even so, most high‐performance photosensitizers are π‐conjugated organometallic compounds represented by Ru(II) complexes. [ 11 ] Noble‐metal‐free organic dyes have also been explored, [ 12–14 ] but are not ubiquitously applied in DSSCs compared to noble metal complexes. Nevertheless, molecular photosensitizers inevitably form heterogeneous interfaces with TiO 2 matrix and electrolyte, and usually require complicated organic synthesis from expensive reagents.…”