Templating Assembly Of ZnO Ordered Porous Films And Their Electrode Performance

In past decades, considerable attention has been given to nanocrystalline photovoltaic cells (NPC) in the field of green energy sources because of its simple process, low cost and large-scale production. In this paper, developments of solar cells, ZnO films and other porous materials prepared by templating method were reviewed. Several templating methods were applied to fabricate ZnO porous films for n-electrode of NPC, and main structure and performances of the ZnO porous films were discussed.Polyethylene glycol (PEG) as templating was used in production of ZnO films and its role in the forming of porous structure was basically investigated. PEG taking zinc oligomers as"gel phase"will exclude and separate with the"flow phase"(solvent admixture) at the structure-directing action of PEG molecular by phase separation mechanism. The final pore of the thin films can be obtained by the volatilization, decomposition and combustion of the"flow phase"and PEG through heat treatment. In this system the best concentration of Zn(CH3COO)2?2H2O is 0.6 mol/L. The pore density and diameter of the ZnO films increase with the molecular weight of PEG and the pore size is about 90~330nm. Moreover, the pore density has a strong dependence on PEG content, water bath temperature, water bath time and solvent. The optical transmittance of the porous film keeps above 80% beyond the wavelength of 430nm. And the band-gap is 3.25eV.The dip-drawing method was firstly used to assemble polystyrene sphere (PS) colloidal crystal templating on glass substrates and fill zinc sol in the interstices of PS templating. The results show that the assembly process of PS templating includes convection of PS, accumulation-nucleation and successive crystallization. The stack structure of the as-assembled templating mostly is face-centered cubic (FCC). Furthermore, the question of sol filling amount that is difficult to be controlled in other methods can be resolved by dip-drawing method. In our experiment, the concentration of zinc sol and dipping time should be 0.3~0.6mol/L and 3min, respectively. And the shrinkage of pore size is about 14.1~33.1%. The calcined film is wurtzite structure and diameter of grain size is about 25nm. The transmittance spectrum shows that optical transmittance of the porous film keeps above 80%...