Synthesis and characterization of Ge doped Cu2ZnSn(S,Se)4 bulk in the presence of reactive liquid phase sintering aid

The quaternary chalcogenide Cu 2 Zn(Sn 1-x Ge x )(S,Se) 4 bulks, where x is G e / [ G e + S n ] molar ratios of 0, 0.15, 0.30, and 0.45 were synthesized via reactive liquid phase sintering at 600 °C for 30 min in the tube furnace and characterized systematically. Together with Sb 2 S 3 as a reactive liquid phase sintering aid, the effects of Ge incorporation on densification, grain boundary, crystal phase purity, crystalline size, and electrical properties were studied. The morphology of the resulted Cu 2 Zn(Sn 1-x Ge x )(S,Se) 4 bulk was found to be more densified and compacted at G e / [ G e + S n ] molar ratio of 0.15 compared to the rests. The X-ray diffraction peaks were shifted towards a higher angle as Ge fraction was increased. The hole concentrations for the entirely p-type bulks were determined to be 3.67 × 10 18 , 1.40 × 10 18 , 1.28 × 10 18 , and 8.90 × 10 17  cm −3  at G e / [ G e + S n ] molar ratios of 0, 0.15, 0.30, and 0.45, respectively. The effects on conductivity and mobility were consistent with their interrelations. Hence, the synthesis and study of Ge incorporated Cu 2 ZnSn(S,Se) 4 bulk using powder technique allows identifying the composition which is expectedly more important for the fabrication of thin film solar cells.