Studies On The Novel Carbon-doped Nanostructured TiO₂ Complex Film Photoeletrode Of Solar Cells

Photoelectrochemical solar cell is defined as the device that can convert the solar energy to the electric power directly according to photovoltaic principle.TiO₂ is believed to be one of the promising candidates for photoanode semiconductor materials in photoelectrochemical cells due to its high thermal stability and photoelectrochemical durability.However,TiO₂ has low solar energy conversion efficiency of less than 5%only absorption in the UV region due to its large band gap of about 3.2eV(anatase).Various approaches also have been considered by different groups to maximize the light-to-electricity conversion eficiency,such as the adding of noble metal nanoparticles(such as Au,Ag and Pt)on the surface of TiO₂,the coupling narrow band-gap semiconductor materials(for example metal oxide or metal chalcogenide),the sensitizing of organic dyes on TiO₂ electrode,incorporation of nonmetallic ion,modification of transition-metal complex,etc.The exploration and discovery the new method and the way to enhance light-to-electricity conversion eficiency still was important issue of current research development high performance photoelectrochemical solar cells. In this paper,carbon-doped nanostructured TiO₂(CD ns-TiO₂) complex film electrode,CD ns-TiO₂/CdS complex film electrode, CD ns-TiO₂/chlorophyll complex film electrode,and CD ns-TiO₂/Cu(L) (â…¡)complex film electrode were prepared by the sol-gel method.And also we investigate photovoltaic performance of photovoltaic cell when the electrode as the photoanode.The results are as follows:1.Carbon-doped nanostructured TiO₂(CD ns-TiO₂)films prepared using titanium ethanolate(Ti(OEt)₄)ethanol solution as precursors by sol-gel method showed excellent photovoltaic activity to absorb visible light.The successful incorporation of the carbon into the ns-TiO₂ host was confirmed by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),scanning electron microscope(SEM),and UV-Visible spectra.The synthesized CD ns-TiO₂ films absorb well into the visible light to near infrared region up to 800 nm and have narrower band gap energy of 1.98(628 nm),1.64(758 nm)and 1.26 eV(958 nm). The doping concentration of carbon in the CD ns-TiO₂ was 41%(as determined from the XPS peaks).We investigated the photoelectrochemical behavior of the CD ns-TiO₂ film photoanode for solar cells,it was found that the CD ns-TiO₂ film photoanode exhibited short-circuit photocurrent(0.265mA/cm²)and an overall conversion efficiency(η)of 4.42%.2.Base on the CD ns-TiO₂ complex film,we further used chemical water bath deposition to prepare CD ns-TiO₂/CdS complex film,and also analyzed the surface morphology,microstructure and property of the films.After CdS was combined,as a result of conduction band,the valence band,the energy gap of two kind of semiconductors are inconsistent,thus folds and enhances the electric charge separative rate of the thin film,causes the spectral response scope of the compound semiconductor to have the red shift,enhances the visible light absorption. And also we investigate Nanostructured Photoelectrochemical Cells(NPC) performance of photovoltaic cell when the electrode as the photoanode, increase the short-circuit photocurrent to 0.53mA/cm²,also improve the light-to-electricity conversion efficiency to 5.16%.3.The TiO₂/chlorophyll a and TiO₂/chlorophyll b complex film electrode were respectively prepared by modifying the chlorophyll a and chlorophyll b which were distilled from the leaves of camphor.The superficial appearance and structure of the complex film were characterized by XRD and SEM and UV-Vis spectra.The light-to-electricity conversion performance of complex film electrodes were investigated by using the photo electrochemical method.The results indicated that a red-shift was observed as result of the chlorophyll being illuminated,a high absorption was observed in both ultraviolet and visible region,enlarge the absorption region,obviously increase the photocurrent,improve the light-to-electricity conversion efficiency of CD ns-TiO₂/chlorophyll a and CD ns-TiO₂/chlorophyll b complex film electrode to 5.4%and 6.2%,respectively.4.The CD ns-TiO₂ complex film were prepared by modifying [Cu(tosyl-L-isoleucine)(2,2'-bipyridyl)](â…¡)(Cu(L)(â…¡))complex which was synthesized newly.UV-Visible spectra and performance of photovoltaic cell were investigated when the CD ns-TiO₂/Cu(L)(â…¡) complex film electrode was used as photoanode.The results indicated that photoresponse of complex film electrode was shifted to visible light even to near-IR,improve the light-to-electricity conversion efficiency of photovoltaic cell to 5.2%.