Real-Time Adsorption and Desorption Kinetics of Dye Z907 on a Flat Mimic of Dye-Sensitized Solar Cell TiO2 Photoelectrodes
Real-Time Adsorption and Desorption Kinetics of Dye Z907 on a Flat Mimic of Dye-Sensitized Solar Cell TiO2 Photoelectrodes
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DOI：
10.1021/jp5015274
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发表时间：
2014-05
影响因子：
3.7
通讯作者：
V. Gusak;E. Nkurunziza;C. Langhammer;B. Kasemo
中科院分区：
文献类型：
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作者：
V. Gusak;E. Nkurunziza;C. Langhammer;B. Kasemo
在TiO2表面形成的染料分子单层是染料敏化太阳能电池的关键组成部分。它通常是通过从溶液中吸附染料分子形成的。染料层应尽可能多地吸收太阳光，并将其转化为光电子，注入到TiO2导带中。为此，染料分子应以适当的分子取向和紧密的填料吸附在TiO2上。采用间接纳米等离子体传感技术实时测量了染料Z907在TiO2薄膜上的吸附和解吸动力学。从动力学曲线中，我们直接推导出了吸附和解吸速率常数，这是以前没有做过的。然后，我们从动力学（通过吸附和解吸速率常数的比值）和用相同的方法、相同的样品和相同的实验得到的测量的Langmuir等温线中推导出平衡吸附常数。考虑到可能的误差来源，这两个值相当一致；因此，我们的方法构成了确定染料- tio2体系更可靠的平衡常数的有效方法。此外，通过测量一系列间歇吸附-脱附步骤，我们发现在每个冲洗步骤后，在给定的覆盖范围内，脱附逐渐减少，从而得出TiO2表面存在不同的结合状态以及染料分子在相当长的时间尺度上发生重组的结论。间断性的冲洗和松散结合分子的解吸似乎加速了重排过程。结果表明，染料浸渍动力学的详细条件可用于优化染料层。
A dye molecule monolayer formed on a TiO2 surface is a key component in dye-sensitized solar cells. It is usually formed by adsorbing dye molecules from a solution. The dye layer should absorb as much solar light as possible and convert the light to photoelectrons, which are injected into the TiO2 conduction band. For that purpose the dye molecules should adsorb on TiO2 with appropriate molecular orientation and close packing. We measured adsorption and desorption kinetics of dye Z907 on thin compact TiO2 films in real time using indirect nanoplasmonic sensing. From kinetic curves, we derived adsorption and desorption rate constants in a direct way, which has not been done for such systems previously. We then derived the equilibrium adsorption constant from both kinetics (by the ratio of the adsorption and desorption rate constants) and from a measured Langmuir isotherm obtained experimentally using the same method, the same sample, and the same experiment. The two values are in reasonably good agreement considering possible error sources; our approach thus constitutes an effective method of determining more reliable equilibrium constants for dye-TiO2 systems. Furthermore, by measuring a series of intermittent adsorption-desorption steps, we found successively less desorption at a given coverage after each rinsing step and conclude that there are different binding states and that reorganization of the dye molecules on the TiO2 surface occurs over rather long time scales. The rearrangement process seems to accelerate by intermittent rinsing and associated desorption of loosely bound molecules. The results suggest that the detailed conditions for the dye impregnation kinetics can be used to optimize the dye layer.