Effect of solvent additives on bulk heterojunction morphology of organic photovoltaics and their impact on device performance. Issue 2 (17th August 2015) - Choi, Won Tae
ABSTRACT: Morphology of the active layer in an organic photovoltaic (OPV) device is known to have a significant impact on the device performance. It is, however, difficult to characterize nanoscale morphologies in detail, especially at the ensemble level. Herein, we report the utilization of small angle neutron scattering (SANS) to investigate variations in the nanoscale morphologies of the active layer of poly(3‐hexylthiophene‐2, 5‐diyl):[6, 6]‐phenyl‐C61 ‐butyric acid methyl ester (P3HT:PCBM) bulk heterojunction OPV depending on the composition of casting solvent. Both the power law and the poly hard sphere model were utilized to characterize the state of the donor and acceptor components, respectively, from the obtained SANS data. Furthermore, the relationship between the nanoscale morphology and device performance is outlined. It was found that the use of 2‐chlorophenol, a poor solvent for P3HT and, at the same time, a very good solvent for PCBM, leads to nanomorphology featuring ordered, highly crystalline P3HT and small (15.2 nm) PCBM domains. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 128–134 Abstract : Mixed solvent processing is a promising method for the fabrication of polymer‐based organic photovoltaics. While most analyses of active layers of organic photovoltaics have been conducted using real‐space imaging techniques, small‐angle neutron scattering is used to study the active layers at the ensemble level. The data, processed through two distinct fitting models, reveal a clear correlation between the nature of mixed solvent systems and the nanoscale morphology of the resulting active layer.