A factorial design of experiments approach to synthesize CZTS absorber material from aqueous media
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A factorial design of experiments approach to synthesize CZTS absorber material from aqueous media Prashant K. Sarswat1, Michael L. Free1 and Ashutosh Tiwari2 1
Metallurgical Engineering, University of Utah, Salt Lake City, UT, United States.
2
Materials science and engineering, University of Utah, Salt Lake City, UT, United States.
ABSTRACT Cu2ZnSnS4 (CZTS), an emerging p-type quaternary chalcogenide, offers many potential advantages as an absorber material. Using factorial design of experiments approach, single stage Cu-Zn-Sn co-electrodeposition from aqueous solution followed by annealing is reported in this paper. Factorial experiments facilitate to study the effects of each factor on the response variable as well as effects of interactions between individual factors on the response variable. Selected factors include concentration of individual ionic species, time of sulfurization and amount of complexing agent, whereas CZTS phase, band gap, carrier concentration, open circuit voltage, and morphological characteristics are the response variables. A model has been developed to show and predict the domain for the best possible factors for CZTS based device fabrication. INTRODUCTION CZTS is a direct band gap material with a band gap of approximately 1.5 eV, and it has a very high absorption coefficient [1-11]. In recent years considerable research has been devoted to synthesizing and investigating CZTS [1-11]. The majority of the research attempts have focused on synthesis techniques such as vacuum based deposition that are difficult to perform for largescale, low-cost production. It is anticipated that the efficiency and cost effectiveness of these devices can be further improved by developing alternate processing techniques, particularly solution based high-throughput electro-chemical techniques. Recently Peter et al. attempted synthesis of CZTS using sequential electrodeposition [12]. It is logical to obtain the desired stoichiometry of electrodeposited component by sequential deposition. In this case, a different bath for each component is used to electroplate each metal layer. Amount of electrodeposited component is related to total electric charge flow in each deposition. The whole process involves 2 additional steps and hence it is time consuming. The single bath electrodeposition technique eliminates an additional electrodeposition step, but formulation of bath composition to achieve the molar ratio 2:1:1 of Cu/Zn/Sn respectively, is difficult. A research group recently reported a single bath recipe of CZTS, though the methodology of formulation is less explored [13]. Design of experiment approach explores the relationship between several experiment input and response variables in a systematic way. THEORY In order to explore the effect of individual components such as the concentration of Zn2+, concentration of Cu2+, concentration of Sn2+,and concentration of complexing agent a
factorial design of experiments was established. In most of the factorial experiments each factor has only two levels (high a
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