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Understanding Interfacial Growth in Vertically Aligned P–N Heterojunctions for Photovoltaic Applications

Objective: To design and develop well defined p-n heterostructures that allow the investigation of their optoelectronic properties due to interfacial interactions.

Approach: Nanowire arrays of SnS/SnS2 p–n heterojunctions are grown on transparent indium tin oxide (ITO) coated-glass and Si/SiO2 substrates via chemical vapor transport (CVT). The nanowire arrays are comprised of individual SnS/SnS2 heterostructures that are highly oriented with their lengths and morphologies controlled by the CVT conditions (i.e. reaction temperature, flow rate, and reaction time).

Results and significance: the direct vapor phase growth of vertically-aligned nanowire arrays of SnS/SnS2 heterostructures is demonstrated. Both SnS and SnS2 are grown within a nanowire thus creating a well-defined p–n nanowire junction. The difference in work function and bandgap between SnS and SnS2 creates an atomically sharp heterointerface, predicted to form a staggering (type-II) band alignment. Substantial control has been obtained over the length and surface coverage of these highly oriented nanowire arrays. For the first time, these SnS/SnS2 heterostructures are incorporated into photovoltaics devices and their optoelectronic properties are elucidated.