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

Abstract

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 γ-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 SiO x and the lateral overgrowth of the CuI seeds into a continuous film. The rectifying p-CuI/SiO x /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.

Epitaxial Electrodeposition of Ordered Inorganic Materials

“…The reaction scheme for depositing CuI(111) onto Si(111) is shown in Figure 4A. 4 An EDTA complex of Cu(II) is electrochemically reduced to produce Cu + in the presence of I − at the Si(111) surface. As shown in Figure 4B, the electrodeposited CuI follows the [111] out-of-plane orientation of the Si(111).…”

“…Our group has recently focused on the electrodeposition of wide-bandgap, transparent hole conductors such as CuI, CuBr, and CuSCN. ,, Data for epitaxial films and nanowires of CuI and CuSCN are shown in Figure . The bandgaps of CuI, CuBr, and CuSCN are 3.2, 3.1, and 3.85 eV, respectively.…”

“…(E) Interface model in which 9 unit meshes of CuI coincide with 10 unit meshes of Si. (A–E) Reproduced with permission from ref , Copyright 2021, American Chemical Society. (F) X-ray diffraction pattern of CuSCN(001) on Au(111).…”

Epitaxial Electrodeposition of Hole Transport CuSCN Nanorods on Au(111) at the Wafer Scale and Lift-off to Produce Flexible and Transparent Foils

“…Electrodeposition is a low cost and highly scalable deposition process producing epitaxial metal and semiconductor films. − Here, we detail an electrochemical method to produce epitaxial CuSCN nanorods on a Au(111)/Si(111) substrate at room temperature from an aqueous CuSO 4 -EDTA-KSCN bath. The material is deposited on a 28 nm-thick layer of Au(111) on a Si(111) wafer that was electrodeposited by a method that we reported earlier .…”

Spontaneous Seed Formation during Electrodeposition Drives Epitaxial Growth of Metastable Bismuth Selenide Microcrystals

“…Methods to synthesize metastable phases at moderate pressure and temperature include colloidal synthesis, ,, chemical and physical vapor deposition, ,− solid-state metathesis, , and electrodeposition. ,− Electrodeposition is particularly attractive because it is a versatile and inexpensive method to produce metals, ,− ceramics, , and semiconductors − ,− at atmospheric pressure and temperatures below 100 °C. Although many binary metallic alloys and intermetallic compounds with metastable structures have been prepared by electrodeposition, ,− there exist only a few examples of electrodepositing metastable phases of semiconductor compounds including Bi 2 Se 3 , − CdSe, and δ-Bi 2 O 3 .…”