Preparation of Cu2ZnSnS4 thin films with high carrier concentration and high carrier mobility by optimized annealing
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The Cu2ZnSnS4 (CZTS) thin film with both high carrier concentration of 3.10 × 1020 cm−3 and high mobility of 19.8 cm2/V/s was prepared with optimization of heat treatment technique. In this work, different heat treatment techniques have been applied for the as-deposited CZTS by electrodeposition method. The as-deposited CZTS thin films have suitable Cu-poor and Zn-rich chemical composition, determining the high carrier concentration. The grain boundaries were designed for enhancement of carrier mobility of the CZTS thin films. Multi-step annealing refined the grains and increased the area of the grain boundaries in the films, resulting in the slight decrease of carrier mobility. Based on multi-step annealing, long and narrow particles and the preferential orientation of the grain boundaries formed by the decrease of Ar flow rate in 550 °C annealing. With such structure, the direct transportation of the holes along the vicinity of the grain boundaries increased carrier mobility.
This work obtained the financial support from National Natural Science Foundation of China (Grant No. 51472020).