A method to crystallize organic semiconductor blends in organic photovoltaic cells is reviewed. This method utilizes a liquid as a non-sticking co-evaporant of small molecular organic semiconductors and crystallizes their single and blend films. Blend films based on H_2Pc and C_<60> with much improved crystallinity have been produced by this method and confirmed by analysis using UV-Vis, XRD and FESEM. Used in organic photovoltaic cells, a variety of blend films, such as blends of fullerene (acceptor) and H_2Pc, PbPc, AlPcCl, and rubrene (donors), have been produced by this method and have achieved striking enhancement of short-circuit current density. In this review, I also present the principle of this new method, co-evaporant induced crystallization. Since it drastically improve the principle of vacuum deposition of organic semiconductors, this method would not be limited for organic photovoltaic cells but also useful for other organic devices.
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