Photoinduced Interfacial Electron Injection Dynamics in Dye-Sensitized Solar Cells under Photovoltaic Operating Conditions

Abstract

We report a pump−probe spectroscopy study of electron injection rates in dye-sensitized solar cell (DSSC) devices. We examine the case of working devices employing an N719 ruthenium sensitizer and an iodide electrolyte. Electron injection is found to occur mainly on a sub-100 fs time scale, followed by a slower component with a lifetime of 26.9 ps, in accordance with previous reports on model samples. The amplitude of this latter component varies with electrolyte composition from 25 to 9%. The appearance of slower components in the electron injection dynamics may be attributed to an aggregated or weakly bound state of the surface-adsorbed N719 sensitizer. Further measurements are reported varying the cell light bias and load conditions, revealing no influence on electron injection dynamics. No other electron injection event is found to occur up to 1 ns. These results show no evidence for a slowdown of electron injection under working conditions compared to model systems for the electrolytes examined in this study. SECTION: Kinetics and Dynamics D ye-sensitized solar cells (DSSCs) can efficiently convert solar radiation into electricity by means of a molecular or quantum dot light harvester anchored on a wide-band-gap mesoporous semiconductor film. Electron injection from the photoexcited light harvester into the conduction band of the semiconductor, typically TiO 2 , is the first reaction in the photoconversion process.

The Impact of the Electrical Nature of the Metal Oxide on the Performance in Dye-Sensitized Solar Cells: New Look at Old Paradigms

“…20,22,62 Such supposition was recently questioned in NIR studies of complete cells and a significant contribution of the triplet state absorption at this wavelength was postulated. 20,22,62 Such supposition was recently questioned in NIR studies of complete cells and a significant contribution of the triplet state absorption at this wavelength was postulated.…”

“…This issue is very important, especially in the view of recent discussions and controversies between the leading groups in DSSC field discussing whether the electron injection in real Ru-based DSSC is mainly ultrafast (femtoseconds) 20,52 or mainly slow (hundreds of picoseconds). However, we can estimate the probable contribution of this process based on the comparison between the transient absorption spectra of the TiO 2 and ZnO solar cells with those of non-injecting Al 2 O 3 cells.…”

“…[8][9][10][11][12] Recent reports point out the importance of the measurements of complete devices rather than the isolated systems to obtain the information relevant for cells under working conditions. [13][14][15][19][20][21][22] The second one is the recently proposed coordinated shifts of interfacial energy levels of the semiconductor as well as those of the dye in DSSC in the presence of typical additives. The primary aim of our studies was to compare the effect of different electrolyte additives on the properties of DSSCs prepared with the standard ruthenium dye N719 (cis-diisothiocyanato-bis(2,2ʼ-bipyridyl-4,4ʼdicarboxylato) ruthenium(II) bis (tetrabutylammonium).…”

Dye aggregation identified by vibrational coupling using 2D IR spectroscopy

“…[1][2][3][4] In these systems, charge is either ejected from the molecule into the semiconductor or the other way around. The efficiency of charge transfer depends on many factors, including the photosensitizer electronic orbitals, conjugation of the linker, and the anchoring groups.…”

More stable and more efficient alternatives of Z-907: carbazole-based amphiphilic Ru(ii) sensitizers for dye-sensitized solar cells

“…The spectra for all three dyes ( Figure 11) show ground state bleaching (GSB) spectral features at wavelength less than 600 nm ( > 2 eV), which has increased transmission, as well as a photo-induced absorption (PIA) band greater than 600 nm, which has decreased transmission. The PIA band is responsive to the charge separation dynamics as it probes the oxidized dye (dye + ), excited state dye (dye*), and the injected electrons in the conduction band of the TiO 2 (eTiO 2 ), as reported previously [51][52][53][54][55][56][57][58] . We compared the charge injection by monitoring the amplitude of the TA signal at 760 nm which corresponds to the absorption for oxidized dye (dye + ) after excitation at 530 nm.…”