Covalent Modification of Photoanodes for Stable Dye-Sensitized Solar Cells

Abstract

This paper describes the surface modification of TiO 2 with 3-aminopropyltriethoxysilane (APTES) followed by covalent attachment of Ru-based N719 dye molecules to TiO 2 through an amide linkage for use as photoanodes (PAs) in dyesensitized solar cells (DSSCs). Attenuated total reflectance− Fourier transform infrared spectroscopy (ATR-FTIR) confirms the surface chemistry between the TiO 2 and dye. The photovoltaic efficiency of DSSCs with covalently linked dye is very similar (6−7%) to that of traditionally prepared DSSCs prepared by direct immersion when both have similar dye coverage. Importantly, the efficiency of PAs with covalently linked dye did not change after storage for more than 60 days in air, whereas the traditionally prepared PAs decreased dramatically after 1 day and lost most of their efficiency after a week. FTIR and UV−vis characterization of the dye suggests that covalent linkage improves stability by preventing the loss of the thiocyanato ligands and/or tetrabutylammonium cations on the dye. PAs with covalently linked dye are also more stable toward water, acid, heat, and UV light compared to traditionally prepared PAs and are more stable compared to other modified PAs with dye attached through electrostatic or hydrogen-bonding interactions.

Desorption retarded optically complemented multiple dye-sensitized photoelectrochemical water splitting system with enhanced performance

“…Further, FTIR spectra (Figs. S6 and S7) clearly shows that the peak at~2160 cm À1 corresponding to SCN peaks is absent in the case of physisorbed dye in contrast to clicked dyes photoanode [15,16]. This further supports the improvement in photo-stability.…”

“…Retarded desorption of dye is attributed to the presence of triazole linkage between dye and P25- TiO 2 as a result of click reaction. Another major challenge associated with the dye-sensitized semiconductor photoanode is self degradation or photo-stability of dye under light [15]. We have chosen RITC and FITC dye to test the photostability because they possess poor photo-stability as compared to N749, N719 and N3.…”

“…organic and ruthenium-based dyes) act as a light harvesting sensitizer and play a key role in photoelectron generation and transfer them to semiconductor [8e12]. However, there are some fundamental challenges associated with DSPEC which limits their long term performance such as: 1) desorption of dye from semiconductor due to hydrolysis of ester linkage between dye and semiconductor in different pH conditions [3,4,13,14], 2) poor binding of dye and increased back electron transfer as a result of dye aggregation/multilayer [15], and 3) limited photo-stability of dyes upon exposure to air/water/electrolyte/heat/light/bias conditions [15,16]. Recently, desorption of dye has been reduced to some extent by anchoring the dyes through phosphonic and silatrane linkages in which later shows better performance [17].…”

In-situ evaluation of dye adsorption on TiO2using QCM

“…The molecular mass of MP13 is only 1.11 times higher than the molecular mass of TPA-C, and we conclude that MP13 forms a considerably denser layer than TPA-C, in line with the smaller equilibrium constant for TPA-C than for MP13. Rinsing removes physisorbed dye and has proven to increase film quality and stability [25], since charge transfer from physisorbed dye to TiO 2 will not be as efficient as when the dye is chemisorbed [7,26,27]. The amount of physisorbed MP13 increases smoothly with solution concentration, whereas for TPA-C the washed-off mass varies less predictably.…”

Increased efficiency of dye-sensitized solar cells by addition of rare earth oxide microparticles into a titania acceptor

“…Interfacial engineering [4] and surface modification of the oxide material are major strategies used to improve the efficiency of DSSCs [5]. This includes depositing a scattering layer of large size TiO 2 particles on top of the active layer [6], controlling the haze of the film by incorporating larger TiO 2 nanoparticles into the film [7,8], chemically modifying the surface of the active layer with molecular linkers [9][10][11], coating the active layer with another metal oxide to form core/shell structures [12,13], and doping the photoanodes with metal ions [14], metal nanoparticles [15,16] or other dopants [17] or metal oxides [18].…”