A major issue that inhibits large-scale fabrication of organic solar modules is the use of chlorinated solvents considered as toxic and hazardous. In this work, composite particles of poly[N-9’-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2’,1’,3’-benzothiadiazole] (PCDTBT) and [6,6]-Phenyl C71 butyric acid methyl ester (PC71BM) were obtained in water from a versatile and a ready-to-market methodology based on post-polymerization miniemulsification. Depending on experimental conditions, size-controlled particles comprising both the electron-donor and the electron-acceptor were obtained and characterized using transmission electron microscopy (TEM), atomic force microscopic (AFM), small-angle neutron scattering (SANS), UV-visible absorption and fluorescence spectroscopies. Intimate mixing of the two components was definitely asserted through PCDTBT fluorescence quenching in the composite nanoparticles. The water-based inks were used for the preparation of photovoltaic active layers which were subsequently integrated in organic solar cells.