Hetero-epitaxial growth of Cu2ZnSn(S1−x,Sex)4-Au nanocomposites: Microstructures and corresponding impacts on optoelectronic properties

Coupling plasmonic gold nanoparticles to sub-stoichiometric copper chalcogenide nanocrystals tends to generate promising nano-heterostructures. We report the research on plasmon-enhanced Cu 2 ZnSn(S 1 − x ,Se x ) 4 -Au nanocomposites (CZTSSe for 0 <  x  < 1, and CZTS if x  = 0), emphasizing on exploring how hetero-epitaxial relationship at Cu 2 ZnSn(S 1 − x ,Se x ) 4 //Au interfaces affects their optoelectronic properties. Digital image processing tools, fast Fourier transform/Fourier inversion, are utilized to extract interfacial epitaxial orientations. We demonstrate that nonnegligible lattice mismatch in short-range order could be equivalently compensated by coincident lattice-matching at certain periodic intervals in a long-range order. By exploring polytypic CZTSSe, we further provide reasonable interpretation of abnormal symmetrical distribution of Au on CZTSSe, which induces lower gold coverage rate and accordingly moderates their localized surface plasmon resonance effect, compared to that of CZTS. It indicates that the shape and phase of CZTSSe should be elaborately controlled to realize optimal multi-site nucleation of heterostructured nanocomposites. As a result, by testing optoelectronic response of solar cells with Cu 2 ZnSn(S 1 − x ,Se x ) 4 -Au films as counter electrodes (CEs), we confirm that a superior hetero-epitaxial interconnection between Au and Cu 2 ZnSn(S 1 − x ,Se x ) 4 can availably restrain interfacial defects of the junction and thus contribute efficient hole transfer/transportation in cathode region. The corresponding balanced electron and hole migration plays a quite significant role in the improvement of open-circuit voltage ( V oc ) and fill factor of photovoltaic devices .