(color online) (a) Schematic drawings of passivation layer with nano-patterned local contacts. (b) SEM images of contact holes on Mo after nanosphere lithography. (c) Cross-sectional TEM image of a bottom Al₂O₃ passivation layer (white dotted square) with a local contact between CZTSe and MoSe₂. Insets are Fourier transform images taken by the area of near the surface (yellow dotted square) and the bulk (red dotted square), respectively. (d) J–V characteristics for the CZTSe solar cells with and wihout a (d) Al₂O₃ and (e) SiO₂ passivation layer at the CZTSe/Mo interface. (f) 10 K photoluminescence spectra of CZTSe solar cells with and without an Al₂O₃ passivation layer at the CZTSe/Mo interface. Reproduced with permission from Ref. [88].