Dye Molecular Structure Device Open-Circuit Voltage Correlation in Ru(II) Sensitizers with Heteroleptic Tridentate Chelates for Dye-Sensitized Solar Cells

Abstract

Dicarboxyterpyridine chelates with π-conjugated pendant groups attached at the 5- or 6-position of the terminal pyridyl unit were synthesized. Together with 2,6-bis(5-pyrazolyl)pyridine, these were used successfully to prepare a series of novel heteroleptic, bis-tridentate Ru(II) sensitizers, denoted as TF-11-14. These dyes show excellent performance in dye-sensitized solar cells (DSCs) under AM1.5G simulated sunlight at a light intensity of 100 mW cm(-2) in comparison with a reference device containing [Ru(Htctpy)(NCS)(3)][TBA](3) (N749), where H(3)tctpy and TBA are 4,4',4"-tricarboxy-2,2':6',2"-terpyridine and tetra-n-butylammonium cation, respectively. In particular, the sensitizer TF-12 gave a short-circuit photocurrent of 19.0 mA cm(-2), an open-circuit voltage (V(OC)) of 0.71 V, and a fill factor of 0.68, affording an overall conversion efficiency of 9.21%. The increased conjugation conferred to the TF dyes by the addition of the π-conjugated pendant groups increases both their light-harvesting and photovoltaic energy conversion capability in comparison with N749. Detailed recombination processes in these devices were probed by various spectroscopic and dynamics measurements, and a clear correlation between the device V(OC) and the cell electron lifetime was established. In agreement with several other recent studies, the results demonstrate that high efficiencies can also be achieved with Ru(II) sensitizers that do not contain thiocyanate ancillaries. This bis-tridentate, dual-carboxy anchor configuration thus serves as a prototype for future omnibearing design of highly efficient Ru(II) sensitizers suited for use in DSCs.

Recent advances in the synthesis and applications of 2,6-dipyrazolylpyridine derivatives and their complexes

“…34 Finally, a 1-bpp/fluorene copolymer that was assembled through multiple Sonogashira couplings 55 ( The most success has been achieved with complexes related to I, bearing thienyl substituents at either the 3-bpp ligand (R 1 ) or the terpy derivative (R 2 ). 53,121 Conjugation of the acceptor ligand to the thienyl group red-shifts the complexes' absorption across the full visible spectrum. Using I, DSCs with photoconversion 85 efficiencies of up to 10.7 % have been prepared, comparable to those using [Ru(NCS) 3 performance to an analogue with the carboxy groups on the bipy co-ligand.…”

Linker effect of ethylenedioxythiophenes in platinum acetylide sensitizers with hybrid starburst donors for dye-sensitized solar cells

“…Up to date, DSSCs have achieved excellent light-to-electrical energy conversion efficiency (g > 12%). With the aim to improving the power-conversion efficiency (PCE), some typical sensitizers, including both pure organic (i.e., metal-free) (Kuang et al, 2008;Qin et al, 2008;Yum et al, 2009;Dentani et al, 2009;Zeng et al, 2010;Zhu et al, 2011;Li et al, 2011;Wu et al, 2012a) and organometallic (i.e., metal-containing) ones (Wu et al, 2012b;Yella et al, 2011b;Daeneke et al, 2012;Kuang et al, 2006;Sauvage et al, 2011), have been successfully designed and characterized. Generally, for those organometallic sensitizers, considerable work has been done to optimize the ligand structure (Kamat et al, 2004;Bai et al, 2008;Wang et al, 2003).…”

New ruthenium complexes (Ru[3+2+1]) bearing π-extended 4-methylstyryl terpyridine and unsymmetrical bipyridine ligands for DSSC applications

“…Recently, p-extended black dye derivatives as well as Ru-bipyridine (bpy) sensitizers have been reported with conversion efficiencies up to $10% [15][16][17][18]. Substitution on tpy ligand with electron donating groups is expected to impart increased electron density on the pyridyl ring, which may decrease the electron accepting character.…”

“…Substitution on tpy ligand with electron donating groups is expected to impart increased electron density on the pyridyl ring, which may decrease the electron accepting character. Theoretical calculations also indicate that the LUMO levels of the Ru-tpy complexes with highly electron rich p-spacer are mainly localized on the carboxyl bipyridine part and not on the pyridyl ring substituted with the electron donating groups [14,15]. On the other hand the electron withdrawing groups on Ru-tpy sensitizers decrease the LUMO level, resulting in more difficult electron injection [15,16].…”

“…Theoretical calculations also indicate that the LUMO levels of the Ru-tpy complexes with highly electron rich p-spacer are mainly localized on the carboxyl bipyridine part and not on the pyridyl ring substituted with the electron donating groups [14,15]. On the other hand the electron withdrawing groups on Ru-tpy sensitizers decrease the LUMO level, resulting in more difficult electron injection [15,16]. Recently, we have achieved a reasonable conversion efficiency (11.1%) using a new p-extended dicarboxylterpyridyl ligand with an electron donating 4-methyl styryl group (HIS-2) [19].…”