The effect of twelve different additives on organic solar cells with an active layer based on poly-3-
hexylthiophene (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) has been studied in this work
and tested for suitability in roll-to-roll slot-die coating. Three of the twelve additives increased the solar
cell efficiency while the rest showed no effect or a negative influence on the efficiency and coatability.
In cases where the additive caused an increase in performance the relation to surface topography and
the structure was investigated using Atomic Force Microscopy (AFM), UV-Vis Spectroscopy and Small
Angle X-ray Scattering (SAXS) for cells prepared with 1-chloronaphthalene (CN), N-methyl-2-pyrrolidone
(NMP) and 1,3-dimethyl-barbituric acid (BARB) as processing additives. The studies suggested that the
use of these additives resulted in films with improved morphology and electrical properties of the active
layer. The effect of the CN on structural evolution during different solvent evaporation and annealing
times was further investigated with an in situ roll-to-roll X-ray study. Lifetime studies under continuous
illumination were used to assess the impact of the additives on the stability of the prepared devices that
had an active area of 1 cm2.