Polymer-Electrode Interfacial Effect on Photovoltaic Performances in Poly(3-hexylthiophene):Phenyl-C61-butyric Acid Methyl Ester Based Solar Cells

The effect of the polymer-electrode interface on the photovoltaic performance of poly(3-hexylthiophene): phenyl-C61-butyric acid methyl ester based solar cells was investigated. Four forms of cathodes, Ca/Ag, Ca/Al, LiF/Al, and Al, were deposited on photoactive films. The Ca/Al cathode showed the best FF of 0.69, while Al produced the worst one of 0.55. The efficiency-limiting effect, a concavity in the fourth quadrant of the current-voltage characteristics, can be caused by a thermally degraded poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) anode or an oxidized Ca cathode. An inorganic material interlayer of CdSe between the photoactive layer and the cathode can, to some extent, inhibit the negative effect of polymer-metal interface.