The Fabrication And Photovoltaic Performance Of TiO₂ Core-shell Nanoarrays Photoanode

One-dimensional TiO2 nanotubes(Titanium nanotubes,TiO2NT)arrays is one of the most widely used photoanodes or conductive materials in the thin film solar cells because of their excellent electron transport properties,match the band position and bandgap width of photoactive materials(such as dyes or organic-inorganic hybrid perovskites,etc.),simple fabrication process and other advantages.In this paper,highly ordered one-dimensional TiO2 NT nano-arrays perpendicular to the substrate are prepared by anodic oxidation and applied to dye-sensitized solar cells(DSSC).On the basis of the direct electronic transmission channel by one dimension array,the core shell nanoarrays photoanode is constructed by introducing the particles and passivation layer on the surface of the TiO2 nanoarrays,which improves the photoelectrical properties of the DSSC by increasing the electron injection and restraining the carrier recombination.The specific research content are as follows:(1)In view of the small surface area and the insufficient dye adsorption of TiO2 nano arrays,the W doped TiO2 nanoparticles were introduced into the TiO2 nanotube,which the TiO2 NT/W-TiO2 NP core shell nano array photo anode was obtained.The introduction of particles increases the surface area of the photoanode and the adsorption and optical capture of the dye.The appropriate amount of W doped into particles can not only introduce electronic traps,inhibit the recombination of the carrier interface,but also regulate the energy of the semiconductor,and improve the injection efficiency of the electrons.The influence of W-doping concentration in TiO2 nanoparticles and sol treatment time on the photoelectric properties of the assembled DSSC was studied in detail.The DSSC efficiency of the TiO2 NT/W-TiO2 NP core shell nanoarray photoanode assembly(the 0.8 wt%W-doping sol treatment 45 min)was 9.47%,which shows increases by 105%in DSSC efficiency,as compared with the photoanode assembled battery without TiO2 nanoarrays(?=4.61%).(2)The thin Al2O3 passivation layer with high dielectric constant and wide band gap was introduced on the surface of Ti02 nanotube by sol-gel soaking and annealing treatment,and the TiO2 NT/Al2O3 NP core shell nano array photo anode was constructed and applied to DSSC.The effects of sol treatment time and sol concentration on the microstructure and the photoelectric properties of the array anode were studied in detail.It was found that the cells that were soaked in the 0.02 M sol for 15 min titanium oxide nanoarray photo anode assembly had the best energy conversion efficiency(? =7.85%),which shows increases by 59%in ?,as compared with the battery efficiency(4.94%)without the passivation layer.It is shown that the introduction of Al2O3 thin passivation layer in the nanoarray photoanode can not only improve the open circuit voltage of the device,but also effectively inhibit the recombination of the I3-ions in the carrier and the electrolyte and the main state of the dye.The appropriate thickness of the Al2O3 passivation layer can effectively tunnel the optical carrier into the TiO2 nanoscale photoanode,Therefore,the photoelectric performance of the battery based on the TiO2 NT/Al2O3 NP core nanoarray photoanode has been significantly improved.(3)Combined with the preceding(1)(2)points,Three aspects of the introduction of particles to increase the photoanode surface area and increase the dye adsorption capacity,an appropriate amount of W doping is introduced to increase the electron injection efficiency from dye to the photoanode,and the introduction of thin Al2O3 passivation layer coated with nanoarrays to suppress carrier recombination at the interface are comprehensively considered.On the basis of the introduction of W doped TiO2 nanoparticles,the Al2O3 passivation layer was further intoduced into the TiO2 NT/W-TiO2 NP core shell nanoarray,that the TiO2 NT/(W-TiO2/AlO3)core shell nanoarray photoanode was constructed.By further optimizing the W-doping concentration,the thickness of Al2O3 passivation layer,and the introduction of nano particles and passivation layer,the TiO2 NT/(W-TiO2/Al2O3)nano-array photoanode assembly by 0.8 wt%W doped sol treated for 45 min and 0.02 M Al2O3 sol treated for 10 min gives a highest power conversion efficiency of 11.20%,which shows increases by 21%in ?,as compared with the DSSC efficiency of TiO2 NT/W-TiO2 NP core shell nanoarray photoanode(9.23%).This research has important significance for improving the efficiency of solar cells from the surface interface modification and design of electronically conductive materials,ascertaining the charge transport mechanism of devices,and promoting the industrial application of solar cells.