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The push coating technique was applied to fabricate a bulk heterojunction PTB7:PC 71 BM organic solar cell. A PTB7:PC 71 BM dichlorobenzene solution was dropped and push-coated on the PEDOT:PSS deposited ITO glass surface with a dimension of 13 x 19 mm 2 , and only 5 µl of the solution was enough to cover the entire surface of the substrate. The thickness variation of the active layer ranged between 25 and 55 nm. The acceptable performance of the fabricated solar cell indicates that the push coating technique will be applicable to polymer solar cell fabrication processes with the minimum loss of the organic semiconductor materials.

Bulk heterojunction solar cells were fabricated using poly [[4,8-bis[(2-ethylhexyl) ) buffer layer, and the effect of the buffer layer on the performance of the solar cells was investigated. The Cs 2 CO 3 layer with a thickness of 0.8 nm significantly increased the short circuit current density, open-circuit voltages and fill factors of the solar cells, presumably because of the better contact between the active layer and the cathode and the work function shift of the aluminum cathode. As a result, the power conversion efficiency increased from 1.09 to 2.12%. However, when thickness of the Cs 2 CO 3 exceeded 2 nm, significant degradation was observed. From the results of a stability test, it was suggested that the inserted Cs 2 CO 3 layer had a minimal influence on the lifetime of the unpakcaged devices.

In this paper, novel fabrication processes for flexible, semitransparent, and nano-meshed Au electrodes on polyethylene terephthalate (PET) substrate utilizing transfer printing from selforganized polymer mold are described. A polycarbonate mold with honeycomb meshed structures was fabricated by a solvent casting method to form self-organized arrays of water bubbles and by drying the water bubbles. It was succeeded to transfer Au electrodes on PEDOT:PSS coated PET substrates using the Aucoated mold under the pressure of 1 MPa at 100 o C for 10 min. The transferred Au mesh has a line-width of 350 nm, a period of 1.5 μm, and a depth of 1.75 μm. The measured transmittance of Au mesh electrode was 34%, and it was less than half of that of an ITO electrode on PET substrate (75%) at photon wave length of 500 nm. However, the measured sheet resistance of the Au mesh electrode is 3 Ω/□, and it was 11 times lower than that of the ITO (33 Ω/□).