The effect of introducing a buffer layer to polymer solar cells on cell efficiency

The effect of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) as a buffer layer was investigated in polymer solar cells (PSCs). Four different types of PEDOT:PSS were used: PH, PHS00 and their DMSO (dimethylsulfoxide)-doped counterparts. The efficiency of PSCs was independent of the electric conductivity of the buffer layer as a bulk property while it was significantly related to interfacial properties between the buffer layer and a bulk-heterojunction (BHJ) layer. The interfacial properties included charge transfer resistance (R-CT), hole mobility (mu(h)) and contact angle (theta) of the solution of BHJ on the buffer layer. Lower R-C, higher mu(h), and smaller theta led to the higher fill factor (up to 72%), enabling highly efficient PSCs with efficiency (eta)=4.25%. (C) 2010 Elsevier B.V. All rights reserved.