Key points are not available for this paper at this time.
Conventional wisdom dictates that the band gap and energy levels of a conjugated polymer are primarily determined by the molecular structure of the conjugated backbone, while the solubilizing alkyl chains should have a negligible impact on these properties. Hence the side chains should have minimal impact on the short circuit current ( J sc ) and open circuit voltage ( V oc ) of corresponding polymer based bulk heterojunction (BHJ) solar cells. Contrary to the “conventional wisdom”, we demonstrate that the side chain of a low band gap polymer ( PNDT-DTBT ) significantly impacts the observed V oc and J sc of the corresponding BHJ solar cell with variations as much as 100%, depending upon the length and shape of these alkyl chains. The observed difference in V oc and J sc is quantitatively correlated with a pre-exponential dark current term, J so, which accounts for the intermolecular interactions in the polymer/PCBM blends.
Yang et al. (2010) studied this question.