Kesterite CZTS nanocrystals: pH‐dependent synthesis

The kesterite Cu2ZnSnS4 (CZTS) nanocrystals (NCs) were successfully synthesized using a relatively simple and one‐step hydrothermal route. The structural, compositional, and optical properties of the kesterite CZTS NCs have been studied in detail. The pH‐dependent CZTS phase formation has been elucidated for the first time. The X‐ray diffraction and Raman spectroscopy confirmed the formation of a main phase kesterite CZTS structure only at pH 7. However, for pH values (4.3, 5, and 9), the formation of CZTS alongwith few secondary phases like Cu2SnS3 (CTS), Cu2−xS, and SnS2/Sn2S3 have been detected. CZTS NCs of size 10–100 nm were obtained at 200 °C and pH 7. The synthesized NCs showed a pH‐dependent variation in optical band gap values from 1.15 to 1.44 eV, which is near optimum value for low cost thin film solar cells.