First Energy Advanced Energy Research Center, Department of Polymer Science, The University of Akron, OH 44325-3909, USA.
Phys Chem Chem Phys. 2018 Jul 25;20(29):19572-19580. doi: 10.1039/c8cp01925h.
Charge transfer between adsorbed dyes and the TiO2 surface plays a key role in controlling the efficiency of dye-sensitized solar cells (DSSCs). The lack of understanding of charge transfer steps has hindered further development of DSSCs and many solar energy conversion devices/processes. In this study, we used in situ infrared spectroscopy to investigate electron transfer and photo-electric energy conversion processes at the interface, i.e., surface hydroxyls, adsorbed species, as well as the dynamics of photo-generated electrons in TiO2 and N-TiO2 in DSSCs. Nitrogen (N-) doping of TiO2 blocked linear OH, giving more hydrophobic surface characteristics than undoped TiO2. N-Doping further increased the electron-hole separation caused by solar light on the working electrode and the current density in the DSSC. In situ infrared (IR) studies revealed that N-doping facilitated the electron transfer from the N719 dye (di-tetrabutylammonium cis-bis(isothiocyanato)bis(2,2-bipyridyl-4,4-dicarboxylato)ruthenium(ii)) to the conduction band in TiO2, reducing the impedance in the DSSC. Probing N-TiO2 with adsorbed ethanol showed that shallow traps in N-TiO2 can be accessed by electrons from adsorbed ethanol. Electron transfer from the N719 dye is significantly faster than that from adsorbed ethanol which involves C-H bond breaking.
吸附染料与 TiO2 表面之间的电荷转移在控制染料敏化太阳能电池 (DSSC) 的效率方面起着关键作用。对电荷转移步骤缺乏了解阻碍了 DSSC 和许多太阳能转换设备/过程的进一步发展。在这项研究中，我们使用原位红外光谱法研究了界面处的电子转移和光电能量转换过程，即表面羟基、吸附物种以及 TiO2 和 N-TiO2 中光生电子的动力学。TiO2 的氮 (N) 掺杂阻止了线性 OH，使其比未掺杂的 TiO2 具有更疏水的表面特性。N 掺杂进一步增加了工作电极上太阳光照引起的电子空穴分离和 DSSC 的电流密度。原位红外 (IR) 研究表明，N 掺杂促进了 N719 染料（二-四丁基铵顺式-双（异硫氰酸根）双（2,2-联吡啶-4,4-二羧酸根）钌 (ii)）到 TiO2 导带的电子转移，从而降低了 DSSC 的阻抗。用吸附的乙醇探测 N-TiO2 表明，N-TiO2 中的浅陷阱可以被吸附的乙醇中的电子访问。N719 染料的电子转移速度明显快于涉及 C-H 键断裂的吸附乙醇的电子转移。
