Kesterite Cu2ZnSnS4 thin films by drop-on-demand inkjet printing from molecular ink

Inkjet printing of kesterite Cu2ZnSnS4 (CZTS) thin films on glass from molecular ink is described. CZTS ink consists of copper acetate, zinc acetate, tin chloride and thiourea dissolved in a mixture of ethylene glycol and isopropyl alcohol. The printed precursor films are vacuum dried and thermolysed at 200 °C in air to obtain CZTS films. X-ray diffraction and Raman spectroscopy of films confirm the formation of kesterite CZTS without any secondary phases. The band gap of the films is 1.48 eV as deduced from transmission spectrum using Tauc plot. The films are p-type with hole density and mobility of 2.65 × 1019 cm−3 and 0.3 cm2V−1s−1, respectively. Measurement of electrical conductivity of films in the temperature range from 77 to 300 K show that dominant mechanisms of conduction are Mott-Variable Range Hopping, Nearest Neighbour Hopping and Thermally Activated Band Conduction in the temperature ranges of 77-155 K, 180-240 K and 250-300 K, respectively.