Giant Incident Photon‐to‐Current Conversion with Photoconductivity Gain on Nanostructured Bismuth Oxysulfide Photoelectrodes under Visible‐Light Illumination

Abstract

Nanostructured layered bismuth oxysulfide films synthesized by chemical bath deposition reveal a giant incident photon-to-current conversion efficiency (IPCE). This study shows that surprisingly for the cathodic photocurrent in the photoreduction process, the IPCE reaches ≈2500% in aqueous solutions containing [Fe(CN) ] . The giant IPCE is observed starting from a certain minimal oxidizer concentration (c > 10 m for [Fe(CN) ] ) and decreases nonlinearly with an increase of illumination intensity. Giant IPCE is determined by the decrease in resistivity of the bismuth oxysulfide film under illumination with photoconductivity gain, which provides the possibility of charge carriers from an external circuit to participate in the photoreduction process. Giant IPCE is observed not only in [Fe(CN) ] solutions, but also in electrolytes containing other photoelectron acceptors: Fe , I , quinone, H O . In all, solution-processed layered bismuth oxysulfide films offer large-area coverage, nontoxicity, low cost, and compatibility with a wide range of substrates. Abnormally high photoelectrochemical activity, as well as a band gap energy value favorable for efficient conversion of solar light (1.38 eV, direct optical transitions), proves the potential of bismuth oxysulfide photoelectrodes for a new generation of high-performance photoconverters.

Bismuth Oxysulfide Photoelectrodes with Giant Incident Photon‐to‐Current Conversion Efficiency: Chemical Stability in Aqueous Solutions

“…Nowadays, there are a number of known bismuth oxysulfide compounds: Bi 2 O 2 S, Bi 2 OS 2 , Bi 3 O 2 S 3 ,, Bi 4 O 4 S 3 ,, Bi 9 O 7.5 S 6 , Bi 10 O 6 S 9 . These materials have a layered structure and are characterized by the pronounced anisotropy of electronic properties . Bi 3 O 2 S 3 and Bi 4 O 4 S 3 are of great interest for superconductive materials design ,.…”

“…Bi 3 O 2 S 3 and Bi 4 O 4 S 3 are of great interest for superconductive materials design ,. Bi 2 O 2 S, Bi 2 OS 2 , Bi 9 O 7.5 S 6 and Bi 10 O 6 S 9 with relatively low band gap energy (0.99–1.38 eV) are the promising compounds for photosensing and solar energy conversion ,,,…”

“…Recently, our group has reported that the bismuth oxysulfide films prepared by the chemical bath deposition (CBD) generate the photocurrent under cathodic polarization and visible light illumination in a contact with aqueous solutions demonstrating incident photon‐to‐current conversion efficiency (IPCE) up to 2500 % . Characterization of the BOS films using scanning electron microscopy (SEM) revealed their layered structure.…”

“…The giant IPCE is determined by a decrease in a semiconductor film resistivity under illumination. It provides the possibility for charge carriers from external circuit to participate in the photoreduction process . The abnormally high IPCE values are observed for cathodic processes in aqueous solutions which contain such acceptors of photoelectrons as [Fe(CN) 6 ] 3− , I 2 , H 2 O 2 and quinone.…”

“…The abnormally high IPCE values are observed for cathodic processes in aqueous solutions which contain such acceptors of photoelectrons as [Fe(CN) 6 ] 3− , I 2 , H 2 O 2 and quinone. The giant IPCE appears starting from a certain minimum oxidizer concentration ( c >10 −3 M for [Fe(CN) 6 ] 3− ) and reduces non‐linearly with the increase of illumination intensity …”