Environmentally friendly preparation of nanoparticles for organic photovoltaics
Abstract
Aqueous nanoparticle dispersions were prepared from a conjugated polymer poly(2,5-
thiophene-alt-4,9-bis(2-hexyldecyl)-4,9-dihydrodithieno[3,2-c:3',2'-h][1,5]naphthyridine-
5,10-dione) (PTNT) and fullerene blend utilizing chloroform as well as a non-chlorinated and
environmentally benign solvent, o-xylene, as the miniemulsion dispersed phase solvent. The
nanoparticles (NPs) in the solid-state film were found to coalesce and offered a smooth
surface topography upon thermal annealing. Organic photovoltaics (OPVs) with photoactive
layer processed from the nanoparticle dispersions prepared using chloroform as the
miniemulsion dispersed phase solvent were found to have a power conversion efficiency (PCE) of 1.04%, which increased to 1.65% for devices utilizing NPs prepared from o-xylene.
Physical, thermal and optical properties of NPs prepared using both chloroform and o-xylene
were systematically studied using dynamic mechanical thermal analysis (DMTA) and
photoluminescence (PL) spectroscopy and correlated to their photovoltaic properties. The PL
results indicate different morphology of NPs in the solid state were achieved by varying
miniemulsion dispersed phase solvent.