SubPc/C60 Bulk Heterojunction Interfaces Using Illuminated KPFM

Abstract

Third generation solar cells are the future of energy collection and storage. Organic photovoltaics (OPVs) made of layers of organic semiconductors are what make up these solar cells, but the material interfaces are still not something that is fully understood. By doing Kelvin-probe force microscopy scans on the bulk heterojunction interface, we are able to understand more about energy conversion from photons to electricity and what materials allow for the highest efficiency. Creating an ‘open-faced’ solar cell by depositing a donor material, boron subphthalocyanine chloride (SubPc), and the acceptor material, buckminsterfullerene (C60), where then MoO3 collects holes that go into the ITO substrate, we are able to determine the photovoltage at the heterojunction. Using Kelvin probe force microscopy (KPFM), the interface can be studied to see the energy band offset of the two materials, calculating the potential difference. Our results show that these organic photovoltaics have a difference in potential of 20-30 mV between dark and illuminated scans.