In order to solve the problem of energy and environmental pollution, solar cells, one kind of efficient utilization of solar energy, have become especially important. Dye-sensitized solar cells (DSCs) have attracted significant attention as a low-cost alternative to commercial solar cells. However, the volatilization feature of traditional high-efficient liquid electrolytes results in decreased efficiency and unsatisfactory stability performance. This limits further practical application. Therefore, it’s necessary to develop alternative electrolytes.

Solvent-free room temperature ionic liquid-based electrolytes have exhibited attractive photovoltaic performance due to their excellent physicochemical properties. However, their present efficiency is restricted and unsatisfactory compared with liquid ones due to the limited types of traditional ILs, low conductivity and high viscosity. In addition, the complex procedures and expensive starting materials of some ILs hinder their further development and application. As a consequence, there remains a great challenge to develop new families of IL-based electrolytes with high conductivity and superior photovoltaic performance.

Recently, researchers developed a new series of soft materials based on ionic liquid-metal complexes (ILMCs) with different metal centers by a simple coordination synthetic method. The obtained complexes are efficient electrolytes of DSCs and exhibite superior photovoltaic performance and remarkable increased conversion efficiencies with a multiple of 1.46-2.63 compared with an IL electrolyte without a metal center. Conversion efficiencies up to 6.38% were achieved based on ILMC electrolytes without any purification, which is comparable to the value of traditional liquid electrolytes. The mechanism investigations clarified the influences of different metal centers on the conversion efficiencies of corresponding devices. The high conductivity and diffusion coefficient of I3− suppressed electron recombination, while low charge transfer impedance contributed to the superior photovoltaic performance of the devices. The advantages of simple composition, high conductivity, superior conversion efficiency along with an easy fabrication method qualify the developed ILMC-based soft materials as promising high-efficient alternative electrolytes of DSCs. The findings presented in this work will provide an effective way for designing new types of electrolytes towards high-efficiency DSCs.

The research team was led by Prof. Zhang Suojiang from the State Key Laboratory of Multiphase Complex Systems of the Institute of Process Engineering (IPE), Chinese Academy of Sciences (CAS).

The research was supported by the National Natural Science Foundation of China (Grant No. 51203161), the State Key Program of the National Natural Science Foundation of China (Grant No. 21436010), the Major Research plan of the the National Natural Science Foundation of China (Grant No. 91434203) and the Key Laboratory of Green Process and Engineering, Chinese Academy of Sciences.

The related previous work was published in Chem. Commun.(2013, 49, 6980-6982). The following work entitled “New series of soft materials based on ionic liquid–metal complexes for high-efficient electrolytes of dye-sensitized solar cells” was published in J. Mater. Chem. A, 2017, 5, 14630–14638 (IF=8.87).

Contact:

Prof. Zhang Suojiang, Director General of IPE, CAS

State Key Laboratory of Multiphase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China.

E-mail: sjzhang@ipe.ac.cn

Source: Institute of Process Engineering, CAS