Cd-free Cu2ZnSnS4 thin film solar cell on a flexible substrate using nano-crystal ink

We have prepared Cu2ZnSnS4 (CZTS) nanocrystals ink using a simple process. Then superstrate-type CZTS heterojunction solar cell with Zinc oxide (ZnO) nanorods-coated on the Indium Tin Oxide (ITO) substrate as a buffer layer was fabricated. X-ray diffraction and scanning electron microscope analysis illustrated wurtzite hexagonal structure of ZnO nanorods in [0001] direction and <20 nm CZTS nanocrystals size. The optical bandgap of CZTS nanocrystals and ZnO nanorods-coated on the ITO substrate were estimated about 1.51and 3.32 eV, respectively. External Quantum Efficiency showed wide optical absorption with a maximum about 57% at 532 nm. The efficiency of 0.83%, open circuit voltage 405 mV, short circuit density 4.35 mA·cm−2 and fill factor 46.9% of cell area were determined. The advantages of our method are appropriate open circuit voltage and facile construction process without using the vacuum which is convenient for commercial purposes.