Department of Engineering Science, Faculty of Informatics and Engineering, The University of Electro-Communications, Chofu, Tokyo, Japan.
Phys Chem Chem Phys. 2012 Apr 7;14(13):4605-13. doi: 10.1039/c2cp23522f. Epub 2012 Feb 22.
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.
了解染料敏化剂和半导体纳米粒子界面的电子转移动力学对于染料敏化太阳能电池（DSC）的基础研究和发展非常重要，DSC 是下一代太阳能电池的潜在候选者。在这项研究中，我们使用瞬态吸收（TA）和改进的瞬态光栅（TG）技术，对新制备的线性连接的双染料共敏化太阳能电池中的超快光激发电子动力学进行了表征，其中锡（IV）2,11,20,29-四-叔丁基-2,3-萘酞菁（NcSn）和顺式-二异硫氰酸根合-双（2,2'-联吡啶-4,4'-二羧酸根）钌（II）双（四丁基铵）（N719）通过金属-O-金属键（即 SnO2-NcSn-N719）连接到纳米晶二氧化锡（SnO2）电极的表面。通过比较 NcSn、N719 和吸附在 SnO2 和二氧化锆（ZrO2）纳米晶薄膜上的混合 NcSn-N719 分子的 TA 和 TG 动力学，阐明了 SnO2-NcSn-N719 中的正向和反向电子转移动力学。我们发现，电子从线性连接的两个染料分子（NcSn-N719）注入 SnO2 有两种途径。第一种是分步电子注入，其中光激发电子首先从 N719 转移到 NcSn，转移时间为 0.95 ps，然后从 NcSn 转移到 SnO2 的导带（CB），有两个时间尺度为 1.6 ps 和 4.2 ps。第二种是从 N719 直接光激发电子转移到 SnO2 的 CB，时间尺度为 20-30 ps。另一方面，从 SnO2 到 NcSn 的反向电子转移时间尺度约为 2 ns，与从 NcSn 到 SnO2 的正向电子转移相比，慢了约三个数量级。从 NcSn 到 N719 的反向电子转移时间尺度约为 40 ps，与从 N719 到 NcSn 的正向电子转移相比，慢了约一个数量级。这些结果表明，光激发电子可以有效地从 N719 和 NcSn 染料注入 SnO2。
