Multiple electron injection dynamics in linearly-linked two dye co-sensitized nanocrystalline metal oxide electrodes for dye-sensitized solar cells

Abstract

Understanding the electron transfer dynamics at the interface between dye sensitizer and semiconductor nanoparticle is very important for both a fundamental study and development of dye-sensitized solar cells (DSCs), which are a potential candidate for next generation solar cells. In this study, we have characterized the ultrafast photoexcited electron dynamics in a newly produced linearly-linked two dye co-sensitized solar cell using both a transient absorption (TA) and an improved transient grating (TG) technique, in which tin(IV) 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine (NcSn) and cis-diisothiocyanato-bis(2,2'-bipyridyl-4,4'-dicarboxylato)ruthenium(II) bis(tetrabutylammonium) (N719) are molecularly and linearly linked and are bonded to the surface of a nanocrystalline tin dioxide (SnO(2)) electrode by a metal-O-metal linkage (i.e. SnO(2)-NcSn-N719). By comparing the TA and TG kinetics of NcSn, N719, and hybrid NcSn-N719 molecules adsorbed onto both of the SnO(2) and zirconium dioxide (ZrO(2)) nanocrystalline films, the forward and backward electron transfer dynamics in SnO(2)-NcSn-N719 were clarified. We found that there are two pathways for electron injection from the linearly-linked two dye molecules (NcSn-N719) to SnO(2). The first is a stepwise electron injection, in which photoexcited electrons first transfer from N719 to NcSn with a transfer time of 0.95 ps and then transfer from NcSn to the conduction band (CB) of SnO(2) with two timescales of 1.6 ps and 4.2 ps. The second is direct photoexcited electron transfer from N719 to the CB of SnO(2) with a timescale of 20-30 ps. On the other hand, back electron transfer from SnO(2) to NcSn is on a timescale of about 2 ns, which is about three orders of magnitude slower compared to the forward electron transfer from NcSn to SnO(2). The back electron transfer from NcSn to N719 is on a timescale of about 40 ps, which is about one order slower compared to the forward electron transfer from N719 to NcSn. These results demonstrate that photoexcited electrons can be effectively injected into SnO(2) from both of the N719 and NcSn dyes.

Ultrafast selective extraction of hot holes from cesium lead iodide perovskite films

“…A femtosecond TA setup was used to study the photoexcited carrier dynamics, especially the hot carrier cooling dynamics in CsPbI 3 [42][43][44][45] . The laser source was a titanium/sapphire laser (CPA-2010, Clark-MXR Inc.) with a wavelength of 775 nm, a repetition rate of 1 kHz, and the pulse width is 150 fs.…”

Characterization of hot carrier cooling and multiple exciton generation dynamics in PbS QDs using an improved transient grating technique

“…In the improved TG technique used for studying the ultrafast carrier dynamics of semiconductor QDs, the laser source was a titanium/sapphire laser (CPA-2010, Clark-MXR Inc.) with a wavelength of 775 nm, a repetition rate of 1 kHz, and a pulse width of 150 fs [18][19][20][21][22][23][24][25][26][27][28]. The light was separated into two parts.…”

“…With ＭＥＧ QD sensitive detection [18][19][20][21][22][23][24][25][26][27][28]. The principle of the improved TG technique has been explained in detail in the previous papers [18][19][20][21][22][23][24][25][26][27][28] and is only described briefly here. A pump beam is incident on the transmission grating and the spatial intensity profile of the pump beam has an interference pattern in the vicinity of the other side of the transmission grating.…”

Kelvin probe force microscopy of nanocrystalline TiO2 photoelectrodes

“…However, many details of the hybrid organic/inorganic interface and the influence of subsequent preparation steps on the device properties, e.g., surface topography and potential, are still unclear and have the potential to increase the efficiency and long-term stability of the devices. Investigations of nanoscaled photovoltaic devices require nanometer-scale measuring methods, including time-resolved measurements of the carrier dynamics [15–16]. Although a DSC photoelectrode consists of a nanostructured TiO 2 , there are few microscopic studies [17].…”