Parameters Influencing the Efficiency of Electron Injection in Dye-Sensitized Solar Cells
Parameters Influencing the Efficiency of Electron Injection in Dye-Sensitized Solar Cells
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DOI：
10.1021/ja8091278
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发表时间：
2009-04-08
影响因子：
15
通讯作者：
Durrant, James R.
中科院分区：
文献类型：
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作者：
Koops, Sara E.;O'Regan, Brian C.;Durrant, James R.
在本文中，我们专注于使用双吡啶基敏化剂染料N719的完全纳米晶钛二氧化二氧化钛染料敏化太阳能电池（DSSC）。通过时间分辨的单光子计数研究了电子注入动力学和量子收率，结果与设备性能相关。在典型的DSSC设备中，发现电子注入动力学从N719三元组状态进行，半场为200 +/- 60 ps，量子产率为84 +/- 5％。我们发现这些注入动力学独立于碘/三碘氧化还原夫妇的存在以及用于合成TiO2纳米颗粒的肽化步骤的pH值。此外，发现它们仅依赖于将电偏置应用于设备上的弱依赖。相反，我们发现这些动力学在很大程度上取决于电解质中丁基吡啶（TBP）和锂阳离子的浓度。该依赖性与TIO2传导带能量的移位相关，这是TBP和LI+浓度的函数，我们得出的结论是，带边缘的100 MEV偏移导致注射动力学的大约2倍延迟。我们发现，从这些瞬态发射数据确定的电子注入量子产率是TBP和LI+浓度的函数，显示了与设备短路密度J（SC）的线性相关性。因此，我们得出的结论是，染料激发态与二氧化钛受体状态的相对能量是DSSC中电子注入动力学的关键决定因素，并且这些能量学的变化以及电子注入的动力学和效率，因此直接在设备光伏效率下。最后，我们从单线与三重态电子注入途径以及动力学冗余性最小化的概念中讨论了这些结果。
In this paper we focus upon the electron injection dynamics in complete nanocrystalline titanium dioxide dye-sensitized solar cells (DSSCs) employing the ruthenium bipyridyl sensitizer dye N719. Electron injection dynamics and quantum yields are studied by time-resolved single photon counting, and the results are correlated with device performance. In typical DSSC devices, electron injection kinetics were found to proceed from the N719 triplet state with a half-time of 200 +/- 60 ps and quantum yield of 84 +/- 5%. We find that these injection dynamics are independent of presence of iodide/triiodide redox couple and of the pH of the peptization step used in the synthesis of the TiO2 nanoparticles. They are furthermore found to be only weakly dependent upon the application of electrical bias to the device. In contrast, we find these dynamics to be strongly dependent upon the concentration of tert-butylpyridine (tBP) and lithium cations in the electrolyte. This dependence is correlated with shifts of the TiO2 conduction band energetics as a function of tBP and Li+ concentration, from which we conclude that a 100 meV shift in band edge results in an approximately 2-fold retardation of injection dynamics. We find that the electron injection quantum yield determined from these transient emission data as a function of tBP and Li+ concentration shows a linear correlation with device short circuit density J(SC). We thus conclude that the relative energetics of the dye excited state versus the titanium dioxide acceptor state is a key determinant of the dynamics of electron injection in DSSC, and that variations in these energetics, and therefore in the kinetics and efficiency of electron injection, impact directly upon device photovoltaic efficiency. Finally, we discuss these results in terms of singlet versus triplet electron injection pathways and the concept of minimization of kinetic redundancy.