We report the performance of polythiophene/fullerene solar cells with a hole-collecting buffer layer that was
made using composite films of functionalized multi-walled carbon nanotube (f-MWCNT) and poly(3,4-
ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS). The MWCNT was functionalized with carboxyl groups to
bestow solubility in a weak base solvent for mixing with PEDOT:PSS. Results showed that the optical transmittance of
the PEDOT:PSS/f-MWCNT composite layer coated substrate sample was slightly improved in some parts of visible and
infrared regions. The polymer solar cells with the PEDOT:PSS/f-MWCNT buffer layer exhibited improved short circuit
current density but other parameters became poorer than those of control device.