Large area polymer solar cells

摘要

The fabrication of very large area polymer based solar cell modules with a total aperture area of 1000 cm~2 has been accomplished. The substrate was polyethyleneterephthalate (PET) foil with a pre-etched pattern of indium-tin-oxide (ITO) anodes. The module was constructed as a matrix of 91 devices comprising 7 rows connected in parallel with each row having 13 individual cells connected in series. The printing of the organic layer employed screen printing of a chlorobenzene solution of the active material that consisted of either poly-1,4-(2-methoxy-5-ethylhexyloxy)phenylenevinylene (MEH-PPV) on its own or a 1:1 mixture (w/w) of MEH-PPV and [6,6]-phenyl-C_(61)-butanoic acid methyl ester (PCBM). Our first results employed e-beam evaporation of the aluminium cathode directly onto the active layer giving devices with very poor performance that was discouragingly lower than expected by about three orders of magnitude. We found that e-beam radiation leads to a much poorer performance and thermal evaporation of the aluminium using a basket heater improved these values by an order of magnitude in efficiency for the geometry ITO/MEH-PPV/C_(60)/Al. Finally the lifetimes (τ_(1/2)) of the modules were established and were found to improve significantly when a sublimed layer of C_(60) was included between the polymer and the aluminium electrode. Values for the half life of 150 hours were typically obtained. This short lifetime is linked to reaction between the reactive metal electrode (aluminium) and the constituents of the active layer.