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Updated: Jun 5, 2026

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
Published on: September 26, 2016
Surface-directed spinodal decomposition in poly[3-hexylthiophene] and C₆₁-butyric acid methyl ester blends
Yana Vaynzof1, Dinesh Kabra, Lihong Zhao
1Cavendish Laboratory, JJ Thomson Avenue, Cambridge-CB3 0HE, U.K.
Abstract:
Demixed blends of poly[3-hexylthiophene] (P3HT) and C₆₁-butyric acid methyl ester (PCBM) are widely used in photovoltaic diodes (PV) and show excellent quantum efficiency and charge collection properties. We find the empirically optimized literature process conditions give rise to demixing during solvent (chlorobenzene) evaporation by spinodal decomposition. Ultraviolet photoemission spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS) results are consistent with the formation of 1-2 nm thick surface layers on both interfaces, which trigger the formation of surface-directed waves emanating from both film surfaces. This observation is evidence that spinodal demixing (leading to a bicontinuous phase morphology) precedes the crystallization of the two components. We propose a model for the interplay of demixing and crystallization which explains the broadly similar PV performance for devices made with the bottom electrodes either as hole or electron collector. The process regime of temporal separation of demixing and crystallization is attractive because it provides a way to control the morphology and thereby the efficiency of PV devices.
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