In the present study, we have investigated the mechanochemical synthesis method as a versatile tool to study the substitution of iodine for sulfur in the BiCuOS structure. Solid solutions with the composition BiCu1-delta OS1-xIx have been obtained up to x = 0.30. In terms of transport properties, the substitution of sulfur for iodine does not affect the bandgap but decreases the charge carrier concentration by n-type doping, as observed from the increase in the electrical resistivity and Seebeck coefficient. The effect of iodine substitution on the copper vacancy concentration delta is also addressed. This study evidences the effective tuning of the optoelectronic properties of BiCuOS with the aim of further integration into optoelectronic devices. Decrease of the charge carrier density with the iodine content in the BiCu1-delta OS1-xIx series in order to meet solar cell requirements.