The Influence of the Columnar Structure in the Active Layer (PMMA/P3HT/PCBM) on the Performance of the Bulk Heterojunction Solar Cell

Abstract

As a novel photovoltaic material, Poly (3-hexylthiophene) (P3HT) has been extensively applied in variety areas such as field-effect transistors, chemical sensors, and photovoltaic solar cell. But its conductivity is unstable due to its poor mechanical properties and environment resistantance. In polymer photovoltaic devices, it is often to combine the conductive polymer with the certain kind of commodity polymer to get a semiconducting-insulating multicomponent system. Our research provides the method to produce ordered self-assembly columnar structure within active layer of bulk heterojunction (BHJ) solar cell by introducing Poly (methyl methacrylate) (PMMA), into the active layer. The blend thin film of PMMA, poly (3-hexylthiophene-2,5-diyl) (P3HT) and Phenyl-C61-butyric acid methyl ester (PCBM) at different ratio are spin coated on silicon wafer and annealed in vacuum oven for certain time. Atomic force microscopy (AFM) images show uniform phase segregation on the surface of polymer blend thin film and highly ordered columnar structure is then proven by etching the film with ion sputtering. The influence of the morphological structures on the performance of the BHJ solar cells will be correlated with the IV-curves tested in the BNL.