The effect of NaCl ink additive on indium oxide nanoparticle thin films is analyzed. NaCl changes the thin film morphology and its chemical structure. NaCl decomposes the nanoparticle shell leading to lower charge transport barriers. Explanation of the increase in field effect mobility from 1 to >12 cm2/Vs. Understanding of the ink drying process and the nanoparticle agglomeration behavior.