Device Characteristics of Hydrazine-Processed CZTSSe
The kesterite Cu2ZnSn(Se1-ySy)4 system, generally referred to as CZTSSe, is an emerging thin-film solar cell technology with many properties necessary for high photovoltaic performance, such as direct band gap, high absorption coefficient and the ability to be deposited by a variety of readily scalable processes. This chapter focuses on the device characteristics of high performance CZTSSe cells, fabricated mostly by hydrazine-based processing. Photoluminescence and quantum efficiency studies give evidence of the existence of band tailing, which is attributed to potential fluctuations induced by strong compensation in CZTSSe. Capacitance spectroscopy reveals distinct characteristics of the CZTSSe films, showing that CZTSSe lacks shallow acceptor impurities. It is yet to be conclusively determined whether CZTSSe devices behave more like Cu2S or like CIGSSe in terms of device stability under various operating conditions. All these concerted efforts will help to realize CZTSSe as a high-performance, Earth-abundant and commercially viable photovoltaic (PV) technology.
