The effect of Zn incorporation on the optical band gap of CuGaS2: Ti thin films

A novel intermediate band (IB) material of Zn incorporation in Ti-doped CuGaS2 thin films has been successfully fabricated via a facile non vacuum method including ball milling, spin-coating and annealing. Experimental results have shown that the IB position of Ti-doped CuGaS2 thin films can be adjusted by Zn incorporation. In this study, the optical band gap has a shortening of 0.19 eV when 0.6% Zn is added to the 1.5% Ti-doped CuGaS2. Due to the Zn addition, the grains grow larger, which is observable from the surface morphology of the thin films using scanning electron microscope (SEM). The energy dispersive X-ray analysis (EDAX) spectrum demonstrates that ball milling can effectively make Ti and Zn elements co-coped evenly into CuGaS2 thin films. Moreover, the improved optical property of the Ti-doped CuGaS2 thin films due to the Zn incorporation also sheds lights in developing new material that could be a potential light absorption layers candidate of high efficiency solar cells.