Effect of molecular weight on the photovoltaic performance of a low band gap copolymer blended with ICBA

Abstract

In this work we fabricated solar cells by combining ICBA as electron acceptor material with various weight fractions of a low band gap electron donor copolymer based on 2,1,3-benzothiadiazole, thiophene and thieno[3,2-b]thiophene units (labeled PPBzT2-CEHb), whose structure is given in Fig. 1 [1]. We investigated the influence of the polymer molecular weight and post-deposition annealing temperature on the solar device performances. Charge transport in pristine polymer films was also studied by measuring the field-effect hole mobility in bottom contact field-effect transistors (OFET).