Organic solar cells based on CuPc and C 60 B. Delgertsetseg, G. Erdene-Ochir, R. Galbadrakh, D. Dorj and C. Ganzorig Department of Chemical Technology, Faculty of Chemistry, National University of Mongolia, University Street I,Ulaanbaatar , Mongolia Kh. Sarangerel and M. Fujihira Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama , Japan Abstract An organic photovoltaic cell is fabricated in this study, with the configuration of indium-tin-oxide ITO/CuPc/C 60 /Al. C 60 acts as an electron acceptor organic material while CuPc corresponds to a donor. The performance under illumination is examined with different organic layer and electrode structures. A cell incorporating 10-nm-thick organic layer of BCP as an exciton blocking layer shows a short circuit photocurrent density (J sc ) of ~3.5 mA/cm 2, an open circuit photovoltage (V oc ) of ~0.45 V, and a fill factor (FF) of ~0.5 with white Xe light illumination with an intensity of 100 mW cm -2. Introduction Organic thin-film photovoltaic (PV) cells have attracted attention because of their ease of fabrication and potential for low-cost production. While donor-acceptor hetero-junction cell with a power conversion efficiency of 0.95% was first reported in 1986 by Tang, it is only recently that the performances of this type organic solar cell have been significantly improved to reach efficiencies in the 3-4% range. Recently, Xue et al. reported power conversion efficiencies (  p ) as high as 4% under 4 suns simulated AM1.5G illumination in a double-heterostructure CuPc/C 60 thin film cell with Ag as the metal cathode. However, such efficiency is not sufficient for practical use, and further improvement is required. Chemical structures of organic materials used for device fabrication Device configurations of (a) ITO(as-cleaned)/CuPc(20 nm)/C 60 (40 nm)/Al two-layer and (b) ITO(as-cleaned)/CuPc(20 nm)/C 60 (40 nm)/BCP(10 nm)/Al three- layer organic PV cells in cross-section J-V bias characteristics of organic PV cells with and without BCP as an exciton blocking layer under 100 mW cm -2 illumination J-V bias characteristics of the organic PV cells with ITO anodes a) as-cleaned, b) modified with –PO 2 Cl 2, c) modified with –SO 2 Cl, and d) modified with –COCl binding groups of p-chlorobenzene derivatives under 100 mW cm -2 illumination Photovoltaic data for the PV cells using ITO chemically modified with –PO 2 Cl 2, –SO 2 Cl, and –COCl binding groups of p-chlorobenzene derivatives Modified ITO anode J sc (mA cm -2 ) V oc (V) FF  p (%) as-cleaned Cl-C 6 H 4 -PO 2 Cl Cl-C 6 H 4 -SO 2 Cl Cl-C 6 H 4 -COCl Conclusion We studied the PV properties of organic cells using the CuPc/C 60 heterojunction layer under 100 mW cm -2 illumination. The PV cells with BCP have more than twice the FF as compared to typical two-layer devices without BCP, resulting in a more than four times of the power conversion efficiency. This study supports the device performance that change in ITO work function and insertion of BCP thin layer are dominate factors in improving PV characteristics in organic thin-film solar cells.