Preparation And Optoelectronic Properties Of The Composite Films Of Inorganic Semiconductors Co-sensitized TiO₂ Nanowire Arrays

Compared with the traditional TiO2 nanoparticle films in sensitized TiO2 solar cells, the one-dimensional TiO2 nanowire arrayfilms (TNWs) has attracted much attention for its large specific surface area and high charge transfer rate on surface. However,Ti02 has limited absorption in the visible light range due to its wide bandgap (-3.0eV for rutile).Previous studies have shown that using two or more different narrow inorganic semiconductor materials together to sensitize TiO2 can effectively broaden its absorption in the visible light region. As the non-toxic and stable Cu2O,Cu2S and CuInS2 have narrow bandgaps, they may be employed as the sensitizers. In this thesis,Cu2O, CU2S and CuInS2 co-sensitized TNWs composite films have been prepred in order to improve the photoelectric conversion efficiency of TNWs film, and their optoelectric conversion properties have been investigated.The detailed research works are as follows:In the second chapter,Cu2O/TNWs heterojunction composite films was prepared by the traditional hydrothermal and potentiostatic electrodeposition methods.To explore optimum experimental conditions for the preparation of Cu2O/TNWs,the factors of applied voltage,reaction temperature,reaction time, length of TiO2 nanowire,and annealing temperature have been explored. The results indicated that Cu2O has successfully deposited on the surface of TiO2 nanowires. Cu2O sensitization can effectively improve the absorption range to 400-500nm in the visible light regionand reduce the electron transport resistance.The open-circuit voltage of CU2O/TNWs was 0.55V and short-circuit current density increases from 0.009 mA /cm2 to 0.34 mA/cm2.In the third chapter, the Gu2S nanoparticles were deposited on the surface of Cu2O/TNWs by ion replacement method, getting the heterojunction composite films of Cu2S-Cu2O/TNWS.TO explore optimum experimental conditions, the factors of reaction time and annealing treatment have been investigated.The results indicated that Cu2O and Cu2S were deposited closely on the surface of TiO2 nanowire. Cu2O and Cu2S co-sensitization can effectively improve the absorption range to 750nm in the visible light region and reduce the electron transport resistance. The open-circuit voltage of Cu2S-Cu2O/TNWs heterojunction composite films increases to 0.62V and short-circuit current density increases to 0.59 mA/cm2.In the fourth chapter,the CuInS2 nanoparticles were subsequently deposited on the surface of Cu2S-Cu2O/TNWs by ion replacement method, getting the heterojunction composite films of CuInS2-Cu2S-Cu2O/TNWs.To explore optimum experimental conditions, the influencing factors of reaction time,concentration of precursor and annealing treatment have been explored.The results indicated that the open-circuit voltage and short-circuit current density of CuInS2-Cu2S-Cu2O/TNWs heterojunction composite films increases to 0.74V and 0.775 mA/cm2.