Eur. Phys. J. Appl. Phys. 37, 287-290 (2007)
https://doi.org/10.1051/epjap:2007002

Optimization of morphology of P3HT/PCBM films for organic solar cells: effects of thermal treatments and spin coating solvents^*

¹ University of Antwerp, Physics Department-CDE, Universiteitsplein 1, 2610 Antwerp, Belgium
² IMEC vzw, Kapeldreef 75, 3001 Leuven, Belgium
³ IMEC, Division IMOMEC, Wetenschapspark 1, 3590 Diepenbeek, Belgium

Corresponding author: Etienne.Goovaerts@ua.ac.be

Received: 29 September 2006
Accepted: 7 November 2006
Published online: 17 January 2007

Abstract

We demonstrate, by means of light-induced EPR and optical spectroscopy, that thermal treatment of P3HT/PCBM films prepared from CB solution results in a decrease of the charge transfer yields. The improved performance of solar cells is therefore attributed to optimization of the morphology, in particular molecular order in the P3HT regions, which could be monitored by optical absorption and resonant Raman scattering (RRS). We further found that spin coating from slowly evaporating solvents leads directly (i.e., without thermal treatment) to optimal morphologies of the P3HT/PCBM films, with similar results for charge transfer, morphology and solar cell efficiencies.