Single source precursor driven phase selective synthesis of Au–CuGaS2 heteronanostructures: an observation of plasmon enhanced photocurrent efficiency

Abstract

The design of new functional metal–semiconductor heteronanostructures with improved photovoltaic efficiencies has drawn significant attention because of their unprecedented properties and potential applications. Herein, we report a phase selective synthesis of ternary CuGaS₂ (wurtzite and tetragonal) by simple solution based thermal decomposition of a new binuclear single molecular precursor [Ga(acda)₃Cu(PPh₃)₂]NO₃ (acda = 2-aminocyclopentene-1-dithiocarboxylic acid, PPh₃ = triphenylphosphine) where the phase selectivity has been achieved easily by changing the combination of surface active agents. Furthermore, we have extended our approach to develop a well-controlled synthetic strategy for the preparation of a Au–CuGaS₂ heteronanocomposite with both the phases. A detailed microscopic study reveals that during heterostructure synthesis, an epitaxial junction has been formed at the interface of ternary CuGaS₂ and metallic Au. To find out the influence of this epitaxial connectivity on the properties, we have studied the photocurrent and photoresponse behavior of the material and compared them with that of bare CuGaS₂. For both the wurtzite and tetragonal phases, the Au–CuGaS₂ twin structure exhibits a plasmon enhanced superior charge transport ability and an abruptly high photocurrent density compared to that of pure CuGaS₂. Due to efficient charge separation by strong plasmon–exciton coupling at the interface, Au–CuGaS₂ can be used as a potential candidate for photoelectrochemical applications.