Ultra-fast co-sensitization and tri-sensitization of dye-sensitized solar cells with N719, SQ1 and triarylamine dyes

Abstract

This paper describes the synthesis of a new, yellow triphenylamine dye, 4-[2-(4-diphenylaminophenyl) vinyl]benzoic acid] (6), with a sorption maximum at 380 nm in solution for which EQE data show shifts to 420 nm on sorption to TiO 2 . The performance of this dye has been measured in dye-sensitized solar cell (DSC) devices, showing h ¼ 2.6% for 1 cm 2 devices. Light soaking of (6) shows excellent long-term stability with <10% variation in device performance over 1800 h. Full characterization data are reported for ( 6) and the intermediates used in its synthesis including single-crystal X-ray structural analysis of all compounds. The paper also describes the ultra-fast dye sensitization and co-sensitization of TiO 2 photo-electrodes in 5 minutes using one or two dyes and the first example of ultra-fast tri-sensitization. The dyes tested include the ruthenium dye N719, the squaraine dye SQ1, the red triphenylamine dye 2-cyano-3-{4-[2-(4-diphenylaminophenyl)vinyl]phenyl}acrylic acid ( 5) and ( 6). DSC efficiencies of 7.5% have been achieved for 1 cm 2 devices co-sensitized using (6) and N719. These efficiencies exceed those recorded for single dye devices and EQE measurements confirm efficient photon capture from two or more dyes in a single photo-electrode. Photo-acoustic calorimetry (PAC) has also been used to measure the energy of the charge separation states formed for (6) and N719, showing a larger value (1.47 eV) for (6) compared to N719 (1.08 eV), whilst a TiO 2 film co-sensitized with both (6) and N719 gave an intermediate value (1.28 eV). These data have been used to calculate dye HOMO, LUMO and l max levels for (6) and N719 leading to important insights for future successful co-sensitization.

Enhanced performance of ruthenium dye-sensitized solar cell by employing an organic co-adsorbent of N , N ’-bis((pyridin-2-yl)(methyl) methylene)- o -phenylenediamine

“…Dehghani co-sensitized N719 dye with a porphyrin dye ZnTCPP, resulting in the efficiency of 6.35%, which was higher than that of 4.75% based on N719 alone [14]. Holliman co-sensitized N719 dye with triarylamine dyes, achieving efficiency of 7.5% which exceeds those records for individual dye devices [15]. Yang reported a co-sensitized system using N719 dye with metal-free organic dye FL.…”

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

“…This inevitably impacts on dye loading with ≈ ⅓ of the dye molecules possible in the thinner films. This limits short circuit current for Ru-bipyridyl dyes such as N719 (ε ≈ 13,500 M −1 cm −1 ) [17] so it is necessary to use sensitizers with ≥ 3 times higher molar extinction coefficient which means organic dyes (e.g. half-squaraine with ε ≥ 100,000 M −1 cm −1 ) [7].…”

“…The process needed to be sped up considerably in order to reduce costs, to make DSC devices a more scaleable PV technology and to improve the reproducibility of the co-sensitization process. In 2010, Holliman et al reported the first ultrafast co-sensitization, with the process taking < 5 min [17] with ultra-fast tri-sensitization reported in 2012 [17]. As NIR sensitizers, squaraines could be used in conjunction with Ru-bipy dyes to harvest more light and therefore improve device efficiency [66].…”

“…Having two dyes absorbing the same wavelengths effectively means the dyes are competing for the same photons, leading to low efficiencies and low J sc . However, two dyes absorbing in different areas of the AM 1.5 solar spectrum can act like a single panchromatic dye, absorbing more photons and producing a higher J sc and therefore a higher η [7,8,17,67]. However, the HOMO/LUMO energy levels (of the different dyes) need to differ sufficiently (> 0.2 eV) from one another to inhibit any electronic interactions between them.…”

Cosensitization of Ruthenium–Polypyridyl Dyes with Organic Dyes in Dye-sensitized Solar Cells

“…Subsequent cosensitizations of rutheniumpolypyridyl dye with SQ1 have been attempted. 32 Recently, we developed a new cis configured squaraine dye, HSQ1, which possesses a dicyanomethylene group on the central squarate unit. 33 This dicyano group forcibly constrained the dye structure as the cis configuration.…”