ИСТИНА

Organic solar cells promise a beneficial combination of efficiency, lifetime, and cost so that they are expected to compete with inorganic solar cells in the nearest future. The most attractive in organic solar cells is that they can be lightweight, flexible, easy compatible with roll-to-roll technologies and, hence, be cheap. The efficiency of organic solar cells has been essentially increased for the last year, and the key milestone in power conversion efficiency of 10% has been reached [1]. Fullerenes are indispensible components of the state-of-the-art organic solar cells, and they are used as an electron acceptor in heterojunction solar cells. Moreover, other nanocarbon materials are promising for organic solar cells, e.g., graphenes can be used as thin-film transparent electrode materials. In this talk, recent achievements in nanocarbon materials for organic solar cells are presented and future trends are discussed. We start with formulation of basic requirements for organic solar cell materials in terms of their electronic, optical and physicochemical properties, and then analyse fullerenes, nanotubes and graphenes. The main focus of the talk is on fullerene derivatives. The drawbacks of pristine fullerenes (C60 and C70) as solution-processed materials for solar cells are their low absorption of solar radiation, too high electron affinity, and low solubility. Because of this C60 and C70 are functionalized to neutralize these drawbacks. Surprisingly, despite active research, the best fullerene derivative for solution-processed organic solar cells is so-called PCBM ([6,6]-phenyl-C61-butyric acid methyl ester or its C70 analog) synthesized 17 years ago [2]. PCBM is appeared to have optimal solubility in organic solvents, but its optical absorption and LUMO energy are too low that limits the photocurrent and the voltage of heterojunction solar cells, respectively. We analyse resent studies on methanofullerenes for solar cells and present our results on the novel type of methanofullerenes, indolinone-substituted methanofullerenes [3]. To decrease the fullerene LUMO energy, fullerenes complexes with metals can be used. Our recent studies on exohedral metal complexes of C60 are presented. The possible ways of fullerene functionalization are discussed. [1] M. A. Green, K. Emery, Y. Hishikawa, W. Warta, and E. D Dunlop, Progress in Photovoltaics: Research and Applications, 20, 12 (2012). [2] J. C. Hummelen, B. W. Knight, F. LePeq, F. Wudl, J. Yao, and C. L. Wilkins, The Journal of Organic Chemistry, 60, 532 (1995). [3] M. I. Valitov, I. P. Romanova, А. A. Gromchenko, G. R. Shaikhutdinova, D. G. Yakhvarov, V. V. Bruevich, V. A. Dyakov, O. G. Sinyashin, and D. Yu. Paraschuk, Solar Energy Materials and Solar Cells (2012) (in press).