A Systematic Approach to Solvent Selection Based on Cohesive Energy Densities in a Molecular Bulk Heterojunction System

Abstract

Abstract The solubilities of 3,6‐bis(5‐(benzofuran‐2‐yl)thiophen‐2‐yl)‐2,5‐bis(2‐ethylhexyl)pyrrolo[3,4‐c]pyrrole‐1,4‐dione ( DPP(TBFu) 2 ) and [6,6]‐phenyl‐C 71 ‐butyric acid methyl ester ( PC 71 BM ) in a series of solvents are measured, and this data is used to calculate the Hansen solubility parameters of the two materials. The dispersion, polar, and H‐bonding parameters of DPP(TBFu) 2 and PC 71 BM were found to be (19.3, 4.8, 6.3) and (20.2, 5.4, 4.5) MPa 1/2 , respectively, with an error of ± 0.8 MPa 1/2 . Based on the solubility properties of the two materials, three new solvents (thiophene, trichloroethylene and carbon disulfide) were utilized for the DPP(TBFu) 2 : PC 71 BM system which, after device optimization, led to power conversion efficiencies up to 4.3%.