Elaboration of PCBM Coated P3HT Nanoparticles: Understanding the Shell Formation

Abigail Palacio Valera,Christophe Schatz,Hiroshi Segawa,Takaya Kubo,Emmanuel Ibarboure,Sylvain Chambon

doi:10.3389/fenrg.2018.00146

Abstract

Solvent displacement, or nanoprecipitation, is a well-known process to develop colloidal dispersions in water. Using two successive and selective nanoprecipitation steps, we developed a method to generate [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) shell on poly(3-hexylthiophene) (P3HT) core nanoparticles (P3HT@PCBM). We report herein on the understanding of the shell formation during this process. Using several techniques (dynamic light scattering, zeta-potential, photoluminescence), we evidenced that after the first solvent displacement with dimethyl sulfoxide (DMSO), the PCBM molecules still dissolved in the medium are already in close interaction with the P3HT nanoparticles (NP). Such proximity of the P3HT core with PCBM molecules in the DMSO dispersion explains why PCBM aggregates around the nanoparticles during the second solvent displacement with water. A fast electron transfer from P3HT to PCBM was identified by transient absorption spectroscopy, confirming the core-shell morphology even for low PCBM concentration. This study opens the route for the development of well-defined nano-objects dispersed in water for fabrication of organic photovoltaic devices with eco-friendly processes.

Highlights

Organic photovoltaic devices present numerous advantages which make them useful for specific markets: flexibility and light weight for portable applications; semi-transparency and shape tuning for integration in building and aesthetic feature (Berny et al, 2015)
When phenyl-C61-butyric acid methyl ester (PCBM) is absent from the initial THF solution (A), we observe that the nanoparticle dispersion is not very stable after the first solvent displacement (SD) with dimethyl sulfoxide (DMSO)
We studied the mechanism of formation of PCBM shell during the two successive solvent displacements

Summary

Introduction

Organic photovoltaic devices present numerous advantages which make them useful for specific markets: flexibility and light weight for portable applications; semi-transparency and shape tuning for integration in building and aesthetic feature (Berny et al, 2015). Organic photovoltaic modules present interesting properties in terms of impact on the eco-systems such as a short energy pay-back time (Espinosa et al, 2011) and low carbon footprint (Lizin et al, 2013). This technology still requires aromatic and/or chlorinated solvents in the organic semi-conductors ink formulations to get high performances. An improvement on the environmental impact is achieved by the substitution of chlorinated solvents by xylene (SchmidtHansberg et al, 2012; Czolk et al, 2016) the use of such aromatic solvents still present a non-negligible impact on the working conditions and the environment.

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