Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (4): 662-668.doi: 10.3866/PKU.WHXB201401242

• ELECTROCHEMISTRY AND NEW ENERGY • Previous Articles     Next Articles

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

LI Jing-Zhe1, KONG Fan-Tai1, WU Guo-Hua1, CHEN Wang-Chao1, HUANG Yang1, FANG Xia-Qin1, DAI Song-Yuan1,2   

  1. 1 Key Laboratory of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, P. R. China;
    2 State Key Laboratory of Alternate Electrical Power Sywtem with Renewable Energy Sources, North China Electric Power University, Beijing 102206, P. R. China
  • Received:2013-11-14 Revised:2014-01-23 Published:2014-03-31
  • Contact: KONG Fan-Tai, DAI Song-Yuan E-mail:kongfantai@163.com;sydai@ipp.ac.cn
  • Supported by:

    The project was supported by the National Key Basic Research Program of China (2011CBA00700), National Natural Science Foundation of China (21003130, 61204075), External Cooperation Program of the Chinese Academy of Sciences (GJHZ1220), and Function and Application Development of Equipment of the Chinese Academy of Sciences (yg2012067).

Abstract:

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 (Rct) 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 (Voc) improved by 47 mV, and the power conversion efficiency of the DSC improved by 10%.

Key words: Dye-sensitized solar cell, Coadsorbent, Interface modification, Electron recombination, Phosphinic acid

MSC2000: 

  • O646