Preparation And Research Of Photoanodes Of Dye-sensitiezed Solar Cells

Due to the very high photo-to-current conversion efficiency (PCE),easy fabrication and low production cost, Dye-sensitized solar cells (DSCs)have attracted more and more attention these years. Photo electrodes, one ofthe heart parts of DSCs, play an irreplaceable role for loading dyes andtransporting electron. As so far, nanocrystalline titanium oxide shows thehighest PCE among various photo electrodes materials. Nanometer ZnOparticles and TiO2particles have similar direct bandgap, position of theconduction band and other physical proper ties. In addition, its fasterelectronic conduction velocity and the simple preparation method make itpossible to replace TiO2. Recently, a new nanocrystallite aggregates, whichare spherical assemblies of nanometer-sized crystallites and feature a sizeon the order of sub-micrometers, can provide huge surface area, good lightscattering performance, easy electron and electrolyte transportation receivemuch attention. This paper will synthetize nanocrystalline ZnO and TiO2submicron aggregates with pores through solventthermal method andsol-gel-hydrothermal method, separately. And then fabricate cells andcompare cells property. Broadband gap semiconductor coating on anode hasbeen researched else.(1)ZnO nanopaticles of20nm has been obtained throughsolventthermal successfully. Then, they are applied to prepare variousthickness of electrodes. Tests show that the absorbing of visible lightaugmented as the thickness of electrodes increases. When the thickness ofelectrode reached to5.5μm, the PCE can be acquired as1.87%which is thehighest. This is mainly due to the compound of injection of electrons and I3-of the electrolyte strengthen as the thickness of zinc oxide increased. Theability of capturing light is dominated when the ZnO film is thin, whileelectron compositing is dominant when it is thick, resulting in IPCE andPCE of the cell was first increased downward trend.A uniform MgO-coatinglayer on ZnO suferce suppresss electron recombination effect. We foundthat the capturing of the light decreased due to the reduction of dye.Hower,the IPCE of the cell was increased when the thickness increase.The VOCincreased by100～142mV, and we obtaind an efficiency of2.27%.(2)The author successfully obtained TiO2submicron aggregates withpores size range from400nm to600nm adopting sol-gel-hydrothermal method, and nanopaticles of20nm through hydrothermal. The preparednanocrystalline titanium oxide and nanocrystallite aggregates are used tofabricate gradient electrodes by changing the amount of the two materials.Studies have shown that the gradient electrodes can acqure more visiblelight and widen wavelength range. In addition, the IPCE and short-circuitcurrent density much larger than that of only nanocrystalline TiO2, and thePCE reached to3.51%. Although MgO coating on the optical surface of thegradient anode increased the open-circuit voltage by109mV and theelectron recombination was inhibited, but IPCE and the short circuit currentdensity were reduced due to the inhibition of electron injection process bythe coating layer.