Influence of selenophene–thiophene phase separation on solar cell performance

Abstract

We compare the morphology and solar cell device performance of selenophene–thiophene copolymers that have the same degree of polymerization and composition, and differ only in their sequence (statistical vs. block copolymers). P3HS-b-P3HT spontaneously undergoes phase separation and P3HS-s-P3HT does not. P3HS-b-P3HT performs best when the intrinsic self-assembled nanostructure is the most perturbed. P3HS-s-P3HT does not undergo intrinsic phase separation, and vapor annealing can be used to optimize the polymer:fullerene morphology, where better nanostructure is well correlated with the best device. While the block structure provides the best stability, the statistical structure is a valuable method to balance the advantage of different monomers while precluding large-scale polymer self-assembly that is a strong intrinsic property of block structure.