Study On TiO₂/PANI Solar Cells

The study of solar cells is always one of the hot points in research fields through the countries, and how to fabricate the low cost solar cells is much more important. Utilized the low cost materials to make high efficiency solar cells is also the goal of all the scientists pursue. In this thesis, we fabricate the organic polymer solar cells with low cost materials, based on PANI and TiO₂. We also get some meaningful results.TiO₂ is a wide band gap semiconductor, it not only has good physical and chemical nature, but have better optical properties. Nano TiO₂ films are porous large surface area, this can be adsorbed more conductive polyaniline materials, internal film grain on the other hand reflect to increase optical path length resulting in the increase absorption of sunlight strength, TiO₂ nano-porous film can guarantee high photoelectric conversion quantum efficiency, and can also ensure high light capture efficiency. Polyaniline has its own unique conductive mechanism in many organic semiconductor materials, low cost and high environmental stability has been hailed as the most potential applications of conductive polymer materials. In this paper, we used polyaniline as a P-type semiconductor material, Nano TiO₂ as N-type semiconductor material to prepare PN heterojunction solar cells.In this paper, we prepared nano-titanium dioxide thin film materials by using the sol - gel. Again we detected the necessary characterization of the fired solid thin film of titanium dioxide by X-ray diffraction analysis, atomic force surface analysis, absorption spectra. Focused on the metal ion-doped titanium dioxide absorption characteristics,We found that the absorption spectra of the metal ion-doped titanium dioxide material red shifted in different degrees, TiO₂-doped alloy Mn0.3Ti0.7O2 red shift absorption spectrum was most apparent, the absorption peak of which relocated near 320 nm, and emergence of a new strong absorption peak at 430 nm was found. We also found that due to the introduction of metal ions, the original TiO₂ lattice structure was destroyed and the alloy material carrier has changed, so that the doped alloy material lost the N-type semiconductor material performance.We used chemical oxidative polymerization method to synthesize original polyaniline materials, the naphthalene sulfonic acid was doped to get conductive polyaniline materials with conductivity of 100 S ? cm-1, and their infrared action spectrum, the absorption spectra and the surface morphology were discussed.This paper reported the heterojunction structure of nano-titanium dioxide / conductive polyaniline, and found its good rectifier effect. (When 2V was carried, titanium dioxide and polyaniline heterojunction had rectifier effect larger than 160.) This for the next phase of the device characteristics of photoelectric conversion provided a theoretical basis.On this basis, for the first time we have prepared ITO/ TiO₂/PANI/ITO structure solar cells, the low-cost material of TiO₂ and the industrialization material of polyaniline have been achieved as the main materials and the production process was simple. And thus the solar cells will greatly reduce the cost. This paper focused on the production technology and processes of solar cell, and we discussed the different infection on the solar cell's open voltage and short current with different methods of preparing the TiO₂ solid film, and we also found the best thickness of the TiO₂ solid film. Solar cells had the best conditions for preparation of four small lipid titanate with anhydrous ethanol volume ratio 1:9, TiO₂ solid film thickness of 70 nm, in this condition, we had the open-circuit voltage of the solar cell of 395 mV, short-circuit current of 38μA (light intensity of 60 mW/ cm²).In addition to this paper, the open circuit voltage of the solar cells, the short-circuit current with the changes in relations between the light intensity and the stability of solar cells were discussed. We found that the short-circuit current with solar light intensity was linear with the change, and the index of the solar cell open-circuit voltage with the light intensity was a linear change, the above conclusions and inorganic solar cell's theory were the same, and we found devices the circumstances in the long run to maintain a relative stability of the open-circuit voltage and short circuit current decreased rapidly with time.On this basis, we also discussed the influence of PEG modification to the surface characterization of titanium dioxide film, and the parameters of the PEG-modified device were measured. We found that the introduction of PEG made a further increase of Nano TiO₂ film surface roughness, in the doping of 60 percent, most rough surface film was got, the open-circuit voltage of PEG-modified cells under conditions in the same light intensity dropped to 296 mV, but the solar cell's short-circuit current increased to 120μA. We believed that because of doping PEG, the surface morphology of titanium dioxide changed, the formation of a more rough surface structure was conducive to the contact of TiO2 and PANI conductive polymer films, and greater contact area was conducive to the production and migration of electrons, resulting in the increasing short-circuit current of the solar cells.Finally, we have made several other structures, mainly on the different electrode materials for the production, and the battery's performance was discussed. Although we still need further work to perfect, but we believe the research of solar cells based on organic polymer solar cells is a hot point in nowadays even in the future. We hope our study will bring some benefit on the research field of organic solar cells.