A method which enables the investigation ofthe buried interfaces without altering the properties ofthe polymer films is used to study vertical phase separation of spin-coated poly(3-hexylthiophene) (P3HT):fullerene derivative blends. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analysis reveals the P3HTenrichment atthefree (air) surfaces and abundance offullerene derivatives at the organic/substrate interfaces. The vertical phase separation is attributed to the surface energy difference ofthe components and their interactions with the substrates. This inhomogeneous distribution ofthe donor and acceptor components significantly affects photovoltaic device performance and makes the inverted device structure a promising choice. KGaA, Weinheim.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics