Tuning of morphological, crystallographic, and optoelectronic properties of CuSCN by electrodeposition

Abstract

Electrodeposition of copper(I) thiocyanate (CuSCN) thin films has been studied in a methanolic solution on variation of the precursor ratio to control morphological, crystallographic, and optoelectronic features of the product. While the one from a stoichiometric bath containing [Cu2+]: [SCN−] = 1:1 results in a randomly oriented crystalline β‐CuSCN, that from a Cu‐rich bath strongly orient the c‐axis perpendicular to the substrate, whereas that from SCN‐rich in parallel. The Cu‐rich film is dense and transparent, whereas the other two are hazy. All of them have an optical bandgap of about 3.6 eV as typically expected for β‐CuSCN, but their p‐type doping level varied to increase the work function from 5.31 to 5.66 eV on increasing the SCN− content, as found by photoelectron yield spectroscopy. This was caused by stabilization of Cu2+ acceptor level in the presence of excess SCN−, as also supported by an enhanced photoluminescence from the d‐d transition of Cu2+ state of such a film. Thus, electrodeposition has proven its usefulness to tailor‐tune optoelectronic properties on demand for device applications.