Synthesis And Photoelectrochemical Properties Of TiO₂/CdS Composite Film Photoelectrodes

Since the last century, environmental pollution and energy shortage of emergency has been high-profile, full use of green pollution-free solar energy resources, environmental pollution and energy into it to solve the shortage of an important way. Thus, TiO₂ is a non-toxic, low-cost and wide application of solar cell materials have become a hot research related to the contents of the researchers. However, due to limitations of its band gap, so that it can only absorb in the ultraviolet part of sunlight (the sun only about 3% to 5%), resulting in lower TiO₂ photoelectric conversion efficiency, the use of sunlight insufficient, and therefore increase its conversion efficiency, more efficient use of solar energy resources. Should be sensitized to their, CdS is ofâ…¡-â…¥compound semiconductor material, its band gap is about 2.42eV, with the right band gap width, long life, the advantages of easy synthesis, which are widely used solar light in the anode. Narrow band gap of CdS, and the location of its conductivity slightly higher than the position of the conduction band of TiO₂, these features can be used to determine their sensitized TiO₂ electrodes.This article uses the sol gel first as well as soaks the rowing motion the method to prepare the TiO₂ nanometer crystal thin film, take ITO as the substrate, the rowing motion different number of times TiO₂ sol, after the heat treatment carries on field launch scanning electron microscope (FESEM) and the XRD diffraction test, we observe prepare the thin film by the even TiO₂ granulometric. The particle size is approximately 50nm, also membrane surface smooth smooth.The film thickness with soaks between the rowing motion number of times to present the direct ratio relations.Qualitative obtains, The thickness of one time probably is 100nm.From the XRD diffraction pattern, the product which obtains for anatase TiO₂, does not have the mixed peak appearance, explained obtains the product is pure.Through to the TiO₂ nanometer crystal thin film light absorption characteristic research discovery, along with film thickness increase, the light absorption scope broaden, the absorption peak strengthens, side the absorption has the red shift towards the long wave direction.When draws out 5 times, side the absorption in 368nm, draws out 15 ratios to draw out 10 times to compare, draws out 15 light absorption strength striving to excel.Through to the different rowing motion number of times ITO/TiO₂ thin film, its photoelectricity characteristic test research indicated that,The film thickness has certain influence to the photoelectricity characteristic.When thickness increase, the photoelectricity current density increases obviously, when in which optimum condition is the film thickness for 1μm, the nanometer TiO₂ thin film photoelectricity current density is approximately 0.23mA. This is because this time membrane matches thick with the semiconductor current carrier mean free path, the photoproduction electron-hole pair may effective carry on separates, thus is advantageous to the current carrier density increase, then enhances the thin film the photoelectricity current density and the photoelectricity transformation efficiency.Uses chemistry water bath law to deposit CdS in the ITO/TiO₂ basis to prepare the compound thin film, the FESEM test result indicated that, the annealing temperature has the remarkable influence to the CdS appearance.In front of the annealing assumes the network structure, becomes smooth after 400℃; the annealing backwall surface, does not have flaking or the crack phenomenon appearance.When the temperature is higher than the optimized temperature, the cadmium sulfide thin film appears the crack, destroyed the membrane integrity.The XRD test indicated that, CdS is the pure cubic structure, has not been oxidized.Temperature formation very important function which ties to the neterogeny.The sample photoelectricity characteristic indicated that, along with the annealing temperature enhancement, the sample photoelectricity characteristic also gradually changes high, if surpasses suitable the temperature to continue the temperature elevation, the photoelectricity characteristic instead reduces.When the nitrogen protection the 350℃annealing, the bias is 0V, the compound thin film photoelectricity current density probably is 0.42mA/cm2, when the annealing temperature continues elevates to 400℃, the photoelectricity current density is biggest, is 0.53 mA/cm2.Continues to elevate the sample the annealing temperature, the photoelectricity current density instead large scale reduces, the showing being suitable annealing temperature is advantageous to is advantageous to the photoelectricity current density large scale enhancement. Respectively makes the light anode take ITO/TiO₂ and ITO/TiO₂/CdS, the TiO₂ thin film in the biasing time photoelectricity current density probably as 0.2mA/cm2, but the compound after thin film, its output photoelectric current density is 0.53mA/cm2.The reason lay in the latter to form the neterogeny knot, the neterogeny knot has caused the photoproduction electron - hole effective separation, has suppressed the photoproduction current carrier compound, lengthened the photoproduction current carrier life.