Hydroxamate Anchors for Improved Photoconversion in Dye-Sensitized Solar Cells

Abstract

We present the first analysis of performance of hydroxamate linkers as compared to carboxylate and phosphonate groups when anchoring ruthenium-polypyridyl dyes to TiO2 surfaces in dye-sensitized solar cells (DSSCs). The study provides fundamental insight into structure/function relationships that are critical for cell performance. Our DSSCs have been produced by using newly synthesized dye molecules and characterized by combining measurements and simulations of experimental current density-voltage (J-V) characteristic curves. We show that the choice of anchoring group has a direct effect on the overall sunlight-to-electricity conversion efficiency (η), with hydroxamate anchors showing the best performance. Solar cells based on the pyridyl-hydroxamate complex exhibit higher efficiency since they suppress electron transfer from the photoanode to the electrolyte and have superior photoinjection characteristics. These findings suggest that hydroxamate anchoring groups should be particularly valuable in DSSCs and photocatalytic applications based on molecular adsorbates covalently bound to semiconductor surfaces. In contrast, analogous acetylacetonate anchors might undergo decomposition under similar conditions suggesting limited potential in future applications.

Light-driven generation of hydrogen: New chromophore dyads for increased activity based on Bodipy dye and Pt(diimine)(dithiolate) complexes

“…The main objective of the present study was to determine whether photofunctional dyads such as 4 were efficient when attached to TiO 2 for electron photoinjection into the semiconductor. The most common method for attachment of light absorbers to TiO 2 nanoparticles is through various anchoring groups such as carboxylate, phosphonate, sulfonate, salicylate, acetylacetonate, catecholate, and hydroxamate (59)(60)(61)(62)(63)(64). In the present study, with phosphonate esters and carboxylate esters as diimine substituents on PtN 2 S 2 chromphores and dyads, attempts to hydrolyze the esters prior to TiO 2 attachment proved problematic because of poor stability of the PtN 2 S 2 moiety under the hydrolysis conditions.…”

Insights into mesoporous metal phosphonate hybrid materials for catalysis

“…Stability is a key index as well from the practical solar cells point of view. Phosphonic linkers were found to represent a promising alternative due to their higher affinity towards the surfaces of metal oxide semiconductors and stronger binding ability than carboxylic grafting groups, 100,101 and they would thus give better long-term stability of DSSCs.…”

A perspective on using experiment and theory to identify design principles in dye-sensitized solar cells

“…Initially used in DSC devices by McNamara et al [54], hydroxamic acids have proved to be extremely stable in water. A study by Crabtree et al compared hydroxamic acid linkers directly with carboxylic and phosphonic acid [55]. Out of these three anchors, hydroxamic acid proved to be superior due to its higher photo-generated current densities.…”