Tuning electronic and photocatalytic properties in pulsed light synthesis of Cu₂ZnSnS₄ films from CuS-ZnS-SnS nanoparticles

We investigate rapid in-situ synthesis of Cu₂ZnSnS₄ (CZTS) thin films via Intense Pulsed Light (IPL) irradiation of solution-deposited and mixed binary CuS, ZnS, SnS nanoparticles (NPs) in ambient conditions. The film phase, composition, morphology, electrical properties, optical properties and photocatalytic activity are characterized as a function of the optical fluence. Crystalline pure-phase kesterite CZTS films with high p-type conductivity of 51 S/cm and optical band gap 1.42 eV are synthesized within 15 s. Surprisingly, using supra-optimal IPL fluence (in 19 s) yields films with a composite CZTS-SnO₂/SnS₂ composition that exhibits about 20% higher photocatalytic efficiency and higher carrier mobility (≈ 120 cm²/Vs) than pure-phase kesterite films. The reaction pathways during IPL irradiation and the resulting film composition are used to understand the enhanced photocatalysis for the supra-optimal fluence. This work will create new avenues for scalable IPL-based bottom-up synthesis of new multinary chalcogenide composites from their binary NPs.