Photocurrent Response of Surface‐Functionalized Metal Oxides with Well‐Matched Energy Levels: From Nothing to Something

Abstract

In recent years, an enormous amount of research has been devoted to the study of photosensitive materials from both fundamental and practical viewpoints, due to their wide applications in photocatalytic and optoelectronic devices, ultraviolet (UV) photodetectors, photoswitch microdevices, light-emitting diodes, photovoltaic devices, and photoelectrochemical cells. Metal oxides, such as ZnO, TiO(2), SnO(2), and NiO have been the most investigated photosensitive materials. To enhance and take full advantage of their photosensitivity, functionalizing their surface with a polymer that has a high light absorption ability has become one of the widely used methods. For example, Z. L. Wang et al. reported that the UV photocurrent of a ZnO nanobelt-based sensor was enhanced by close to five orders of magnitude after functionalizing its surface with polystyrene sulfate which has a high UV absorption ability. T. Sasaki et al. reported the assembly of a TiO(2) nanoparticle film with poly(3,4-ethylenedioxythiophene) and poly(4-styrene sulfonate) (PEDOT-PSS) through layer-by-layer fabrication in the nanometer scale. The electric conductivity of the TiO(2) composite films could be tuned by UV and visible (Vis) light. Thus, sunlight or photon energy can be used and transformed to electrical energy by UV-photosensitive metal oxides after their surfaces have been functionalized with a dye that has a high Vis absorption ability. To date, most of the dye-sensitized solar cells are based on the surface functionalization of UV-photosensitive metal oxides by dyes. However, to the best of our knowledge, all of the reports on surface functionalization enhanced only the UV photosensitivity of the metal oxide. In other words, this method has been used exclusively to enhance the UV photocurrent in metal oxides that already have UV-photosensitive properties, but not to induce UV photocurrent in metal oxides that have no UV-photosensitive properties. In fact, to the best of our knowledge, there are no surface-functionalizing reports on inducing UV or Vis photocurrent in metal oxides that have no UV- or Vis-photosensitive properties.

Synthesis of TiO2–polyaniline core–shell nanofibers and their unique UV photoresponse based on different photoconductive mechanisms in oxygen and non-oxygen environments

“…1 Nevertheless, it still remains a challenge to maintain good connection between the two different constituents in the junction, which is helpful for enhancing the optoelectronic properties and charge carrier mobility. 16 Following our extensive explorations of the synthesis of the optoelectronic materials and the construction of p-n junction nanodevices, [17][18][19][20][21] here we expect to choose proper p-and n-type semiconductors to fabricate 1D core-shell heterostructures. This kind of fiber-type heterojunction is beneficial to the integration of high-quality nanodevices, due to the expanded junction area and short collection lengths of the excited carriers.…”

“…24 In this communication, we have fabricated TiO 2 -PANI core-shell nanofibers via an easy method. According to our design, upon using different mechanisms of well-matched energy levels 17,18,25 and the increased thickness of the depletion region of the p-n heterojunction 21 between the TiO 2 core and the PANI shell, respectively, an increase and a decrease in photoconduction were observed in a non-oxygen and an O 2 environment, respectively.…”

Architecture designed ZnO hollow microspheres with wide-range visible-light photoresponses

“…In recent years, an enormous amount of research has been devoted to the study of photosensitive materials, from both fundamental and practical viewpoints, due to their wide applications in photocatalytic and photoelectronic devices, ultraviolet (UV) detectors, photoswitch microdevices, light-emitting diodes, photovoltaic devices, and photoelectrochemical cells. [1][2][3][4][5][6][7] Metal oxides such as ZnO, TiO 2 and SnO 2 have been the most investigated photosensitive materials. [8][9][10] To enhance and take full advantage of the photosensitivity of metal oxides, a lot of strategies have been proposed to increase the photoresponses especially in the visible-light range, such as surface polymerization, light-element doping, or surface plasmon enhancement.…”

Conductive MoS2 Quantum Dot/Polyaniline Aerogel for Enhanced Electrocatalytic Hydrogen Evolution and Photoresponse Properties

“…There are some reports of photoresponse property of the PANI hybrids and also in their gel/xerogel states. In 2012, Yang et al have synthesized Bi 2 O 3 –PANI and V 2 O 5 –PANI nanocomposites showing photocurrent enhancement of 10 –2 and 10 –4 mA under UV light irradiation at 1 V, respectively . Recently, from our laboratory, Bairi et al have reported 5,5′-(1,3,5,7-tetraoxopyrrolo­[3,4- f ]­isoindole-2,6-diyl)­diisophthalic acid (PMDIG)–PANI hydrogel, which has exhibited photocurrent rectification property under white-light illumination .…”