Optoelectronic Switches Based on Wide Band Gap Semiconductors

Abstract

Switching of photocurrent direction in semiconducting systems upon changes of the electrode potential or incident light wavelength was realized by a series of photoelectrodes covered with titania modified with pentacyanoferrate complexes, [Fe(CN)(5)L](n)(-) (L = NH(3), thiodiethanol, thiodipropanol). These materials were characterized by optical spectroscopy and electrochemistry. The structure of the surface complexes was modeled using simple quantum-chemical models. The electrodes described in this paper enable control of the photocurrent direction by two stimuli: Changing the wavelength or the photoelectrode potential easily switches the direction of photocurrent. The materials are different from those of similar characteristics studied by other authors: They are not composites comprising of two types of semiconductors but rather engineered uniform materials. The photocurrent switching phenomenon is an intrinsic feature resulting from a specific electronic structure of the surface-modified semiconductor.

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO2‐Based Nanomaterials

“…In the latter approach, 2 Advances in Physical Chemistry transition metals [86][87][88] or main-group elements like carbon [35,89], nitrogen [31,[90][91][92][93][94][95][96][97], and sulfur [98,99] are introduced into the lattice of titania resulting in formation of intrabandgap donor and acceptor levels, allowing thus for visible light (λ > 400 nm) excitation. Apart from the fields of solar cells and photocatalysis, the visible light-responsive TiO 2 materials opened up a route for further developments including photoelectrochemistry-based sensors [100,101] and light-addressable photoelectrochemical optoelectronic devices [102][103][104][105][106].…”

Photosensitization and the Photocurrent Switching Effect in Nanocrystalline Titanium Dioxide Functionalized with Iron(II) Complexes: A Comparative Study

“…This absorption can be tentatively attributed to the chargetransfer transition similar to that observed for diverse cyanoferrate complexes bound to the titania surface. [63][64][65][66]74] A completely new type of electronic transition appears after adsorption of hexacyanoferrate complex at TiO 2 surface. The broad band with maximum at 415 nm recorded for [Fe(CN) 6 , is attributed to the MMCT transition, namely Fe II !Ti IV .…”

A Hybrid Semiconductor Electrode for Wavelength‐Controlled Switching of the Photocurrent Direction

“…[3, 4] Observations of wavelength-dependent changes in photocurrent direction have been reported for several different systems, such as metal-chlorophyll-metal sandwich cells, [5] gold electrodes covered with helical peptides containing various chromophores, [6] polymer multilayers, [3] and a ruthenium complex linked to viologen and a palladium phthalocyanine derivative.[7] Bilayers or core-shell composites of organic polymers and TiO 2 , [8] as well as TiO 2 modified with Fe II complexes [4,9] or with a ruthenium cluster dye also show these effects.[10]Herein we report the fabrication and characterization of a novel photoelectrode that exhibits unusually sharp wavelength-controlled switching of photocurrent direction. The electrode is a hybrid assembly of two inorganic nanocrystalline semiconductors-nitrogen-modified TiO 2 (TiO 2 -N, an ntype semiconductor) and CuI (p-type)-deposited on conducting indium-tin oxide (ITO) glass.…”