title: Rapid precipitation: an alternative to solvent casting for organic solar cells.
abstract: Rapid precipitation, immersion of a liquid formulation into a nonsolvent, is compared with drop casting for fabricating organic solar cells. Blends comprising poly-3-hexylthiophene (P3HT), phenyl-C61-butyric acid methyl ester (PCBM), and chlorobenzene were processed into bulk samples by using two distinct routes: rapid precipitation and drop casting. The resulting structure, phases, and crystallinity were analyzed by using small-angle neutron scattering, X-ray diffraction, differential scanning calorimetry, and muon spin resonance. Rapid precipitation was found to induce a finely structured phase separation between PCBM and P3HT, with 65 wt % crystallinity in the P3HT phase. In contrast, solvent casting resulted in a mixed PCBM/P3HT phase with only 43 wt % P3HT crystallinity. The structural advantages conferred by rapid precipitation were shown to persist following intense thermal treatments.
authors: Centre for Plastic Electronics, Imperial College London, London SW7 2AZ (UK); Department of Chemical Engineering, Imperial College London, London SW7 2AZ (UK).
authors: Rajeev
authors: R
authors: Dattani
authors: Mark T F
authors: MT
authors: Telling
authors: Carlos G
authors: CG
authors: Lopez
authors: Siva H
authors: SH
authors: Krishnadasan
authors: James H
authors: JH
authors: Bannock
authors: Anne E
authors: AE
authors: Terry
authors: John C
authors: JC
authors: de Mello
authors: João T
authors: JT
authors: Cabral
authors: Alisyn J
authors: AJ
authors: Nedoma
keywords: crystal growth; organic solar cells; phase transitions; rapid precipitation; small-angle neutron scattering