Fabrication of Cu2ZnSnS4 thin film solar cell using chemical method

We report the growth, characterization and fabrication of the quaternary compound semiconductor Cu₂ZnSnS₄ (CZTS) thin film solar cell using low temperature chemical synthesis. The constituent materials required for this p-type absorber are earth abundant and available at low cost. In addition, CZTS has large absorption coefficient in the order of 104 cm-1 and has optimum band-gap energy of about 1.5 eV required for an efficient photo-energy conversion. We have adopted a low temperature chemical route followed by spin coating to synthesize CZT layers. Essentially, a metal compound solution of CZT is formed by dissolving Copper (II) acetate, zinc (II) acetate and tin (II) chloride in 2-methoxyethanol and monoethanolamine. The CZT layer, which is formed by spin coating and annealing at around 300°C, is then sulphurized by using a safe organic sulphur source called di-tert-butyl-disulfide (TBDS) for a controlled sulphur transfer at temperature around 400°C to form stoichiometric Cu₂ZnSnS₄. The Cu to Zn+Sn and Zn to Sn ratios for an optimally synthesized film were 0.87 and 1.2 respectively. Techniques like EDX, XRD and XPS were used for composition, crystallinity and phase analysis.