Epitaxial Electrodeposition of Optically Transparent Hole-Conducting CuI on n-Si(111)

The expansion of future optoelectronic materials into transparent flexible electronics, perovskite, organic, and tandem photovoltaics depends on the development of high-performance p-type materials with optical transparency. We introduce the epitaxial growth of gamma-CuI, a wide band gap p-type semiconductor with the zinc blende structure, on single crystalline Si(111) using a simple, cost-effective, room-temperature electrochemical method. The deposited epitaxial film grows with a high degree of in-plane and out-of-plane order, templated by the Si(111) substrate. A deposition mechanism is proposed, in which epitaxial CuI seed crystals are nucleated on the freshly etched n-Si(111) surface, followed by the simultaneous oxidation of Si to form a thin layer of SiOx and the lateral overgrowth of the CuI seeds into a continuous film. The rectifying p-CuI/SiOx/n-Si heterojunction diode shows an ideality factor of 1.5, a built-in voltage of 0.67 V, and a barrier height of 0.91 eV. The epitaxial CuI film has been epitaxially lifted off by chemical etching to produce textured CuI foils with an out-of-plane and in-plane order that mimics that of single crystals.

Automated summary

The development of future optoelectronic materials relies on the high-performance p-type materials with optical transparency. Epitaxial growth of gamma-CuI on single crystalline Si(111) using a room-temperature electrochemical method demonstrates high in-plane and out-of-plane order. The deposition mechanism involves nucleating CuI seed crystals on n-Si(111) and simultaneous oxidation of Si to form SiOx, resulting in the lateral overgrowth of CuI seeds into a continuous film.