Electrical conduction of CZTS films in dark and under light from molecular solution ink

• Dark and photoconductivity of CZTS films has been investigated from 77 to 300 K.
• The films were granular and show micro porosity.
• NNH and TE over GB barriers of flower like CZTS grains have been studied.
• Hopping energy and GBB decreases upon illumination.

Cu2ZnSnS4 (CZTS) films were deposited by doctor blade printing from molecular solution ink. The molecular ink of metal-thiourea complex was synthesised without any capping in glutinous ethylene glycol. The resulting precursor films were subjected to heating in a furnace at 473 K in air and finally annealed at 623 K and 673 K, respectively for 1 h in argon atmosphere. The films were pure kesterite CZTS as revealed from X-Ray diffraction and Raman spectroscopy. Electrical conductivity and hole mobility of the CZTS films increase with increasing annealing temperatures. The films were p-type and shows photoconductivity. To find out the dominant conduction mechanisms in these CZTS films, temperature variation of dark and photoconductivity has been investigated in the temperature range of 77 to 300 K. Both as-prepared and annealed films show nearest neighbour hopping below 200 K, while above 200 K the films dominated thermionic emission over grain boundary barriers.