Influence of Processing Experimental Parameters of PEDOT: PSS on the Photovoltaic Performance on CdTe Solar Cells

Hybrid CdTe solar cells including the organic polymer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) in the typical structure were fabricated. PEDOT:PSS was added as a p+ region in the structure of solar cells after CdTe deposition and before the processing of the Cu-Mo back contact and was compared with a CdTe reference solar cells without polymer. The PEDOT:PSS was deposited at different rotational speeds of 3000 to 6000 rpm for 30 s, by spin coating technique. The obtained thicknesses were around 20-40 nm. Adequate coverage of the CdTe surface and grain morphology was obtained, when the polymer was deposited at 5000 rpm of rotational speed this according to Scanning Electron Microscope measurements. The final structure of the solar cells was SnO₂:F/ZnO+CdS-TT/CdTe+CdCl₂-TT/PEDOT:PSS/Cu-Mo. In our results was clear that the solar cells with PEDOT:PSS processed at different rotational speeds had higher fill factor and thus higher photovoltaic efficiencies. A high photovoltaic efficiency of around 13% was obtained when PEDOT:PSS was deposited at 5000 rpm and the Cu-Mo back contact was processed with a substrate temperature of 200 °C. A particular increment in the photovoltaic efficiency of solar cells close to 8% was achieved, when the Cu-Mo back contact was processed at room temperature.