Low-Cost Fabrication of Organic Photovoltaics and Polymer LEDs - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 247

Fig. 23 The coating quality images of the blade-coated layers versus spin-coated layer. Defects
can be seen in the latter

Table 7 The relationship between the blade speed and thickness of the P3HT:PCBM solution
Blade speed (mm/s) 8 12 16 20 24

Thickness (nm) 174.0 247.1 281.8 351.0 368.9

resistance and the fill factor, the overall power conversion efficiency will depend
on the surface morphology. The film thickness can be controlled by modifying the
coating speed. As discussed in the previous section, the film thickness is well
matched by the theoretical relationship between the blade-coating speed and the
film thickness as shown in Table 7 . Higher speed leads to thicker film as shown in
Fig. 24 .

2.5.2 Device Performance in the Roll-to-Roll Processed Conventional
Structure in Solar Cells

Conventional OPVs with the structure of ITO-glass/PEDOT:PSS/P3HT:PC 61 BM/
LiF/Al was fabricated as a control device. Among the functional layers, inorganic
layers such as ITO, LiF, and Al cannot be coated by roll-to-roll process. However,
the ITO can be replaced by polymer anode on PET substrate. The polymer anode
was coated by roll-to-roll coating method. Low conductive PEDOT:PSS (AI4083)
as a hole extraction layer and P3HT:PC 61 BM donor-acceptor blend as polymer
active layer were then roll-to-roll coated at air atmosphere. The layer thicknesses
were 50 and 200 nm respectively. The LiF (1 nm) and Al (80 nm) were thermally
evaporated in the vacuum chamber at a base pressure of 10 -6 mbar.