长链双烷基次膦酸作为共吸附剂修饰TiO_2光阳极

对TiO2/染料/电解质界面进行修饰是提高染料敏化太阳电池(DSC)性能的有效手段,其中引入共吸附剂有机小分子和染料共同吸附在TiO2表面是一种简单有效提高DSC性能的方法.本文合成了长链的双正十二烷基次膦酸(DDdPA)作为染料的共吸附剂应用于染料敏化太阳电池.通过红外光谱(FT-IR)表征DDdPA在TiO2表面的吸附;借助电化学阻抗谱(EIS)及强度调制光电流谱(IMPS)/强度调制光电压谱(IMVS)等技术表征了电子的传输与复合动力学过程.研究发现,DDdPA可以很好地与染料共同吸附在TiO2表面;与二(3,3-二甲基丁基)次膦酸(DINHOP)相比,DDdPA的引入可以更好地抑制TiO2/染料/电解质界面处的电子复合;在优化浓度配比下,DDdPA的引入有效提高了器件的电子寿命,使TiO2导带边负移约30 mV,最终使器件的开路电压提高了47 mV,光电转换效率提升约10%.

Di-n-alkylphosphinic Acid with a Long Alkyl Chain as a Coadsorbent for Modifying TiO2 Photoanodes

The modification of a TiO₂/dye/electrolyte interface can effectively improve the performance of dyesensitized solar cells (DSCs). A variety of methods has been reported for the modification of this interface, among which the introduction of a small organic molecule co-adsorbed with the dye on the surface of TiO₂, which is simple and effective. In this paper, di-n-dodecylphosphinic acid (DDdPA) was synthesized and used as a coadsorbent in a Z907 based dye-sensitized solar cell. Its good adsorption property on the surface of TiO₂ film containing Z907 was confirmed by Fourier transform infrared (FT-IR) spectroscopy. The dynamic processes of electron transport and recombination were investigated by electrochemical impedance spectroscopy (EIS) and intensity-modulated photocurrent spectroscopy (IMPS)/intensity-modulated photovoltage spectroscopy (IMVS). Compared with the widely used bis-(3,3-dimethyl-butyl)-phosphinic acid (DINHOP) coadsorbent, the DSC based on DDdPA is more effective in reducing electron recombination as shown by the EIS measurement, and this is mainly owed to the longer alkyl chain and the more pronounced steric hindrance effects. With an optimized concentration ratio of Z907 to DDdPA of 2:1, the charge transfer resistance (R_ct) is larger than that of the device with only Z907 and an optimized Z907-to-DINHOP ratio of 1:1. IMPS/IMVS measurements indicate that the introduction of DDdPA effectively enhances the electronic lifetime and leads to a negative shift of about 30 mV for the conduction band edge. With the optimized DDdPA concentration, the open-circuit photovoltage (V_oc) improved by 47 mV, and the power conversion efficiency of the DSC improved by 10%.