Ink - based non-vacuum process of synthesis of multicomponent Cu2ZnSn (Se1-x,Sx)4 for use in low-cost photovoltaic absorbers

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In this present work, Cu2ZnSn(Se1-x,Sx)4 nanocrystals with tunable band gaps have been synthesized via hot injection method in conjunction with TOP/TOP capping ligands. By varying the input precursor ratio Se/( S + Se), by adjusting the composition parameter x from 0 to 1.0, the band gaps of the CZTSSe-based nanocrystals can be linearly tuned from 1.2 to 1.5 eV respectively. For CZTSSe-based nanocrystals, high intensity of XRD peak corresponding to (112) direction revealed that the growth is oriented along (112) direction and its intensity increases with increase in Se/(S + Se) input precursor ratio. As the Se-content increases, the larger Se atoms (1.98 Å) replace the smaller larger S atoms (1.84 Å) resulting in an increase in the lattice parameters as shown by the shift of the XRD peaks to lower values of 2θ.XRD studies reveal the presence of stable kesterite phase although the presence of either stannite phase or both cannot be ruled out completely. It has been found that CZTSSe nanocrystallites owing to its high crystallinity and well-ordered 3-dimensional network and hence controlled morphology in its pristine form as compared with CZTSe, CZTS counterparts exhibits higher homogeneity, resistance against agglomeration and eventually higher current-voltage characteristics. To, the best of our knowledge, this is the first detailed report on the synthesis of multicomponent Cu2ZnSn(Se1-x,Sx)4 nanocrystals by hot injection method via the usage of both TOP (trioctyl phosphine) & TOPO (trioctyl phosphine oxide) capping ligands. The primary technological advantage of creating nanocrystals by this solution based method is the capability to easily form an ink that is compatible with a large variety of scalable film formation or printing processes for photovoltaic applications. Copyright © 2016 VBRI Press.