Preparation And Photovoltaic Property Of DSSC&PSC Based On Hydrgenated Titania Nanomaterials

Dye sensitized solar cells?DSSC?and perovskite solar cells?PSC?have become the most promising solar cells due to their unique advantages.In these two kinds of battery systems,TiO₂ plays an important role in carrier support and electron transport.There are three main problems existing in TiO₂ based solar cells: poor light trapping ability in visible and near infrared region,leading to the poor absorption spectrum of device;the wide band gap,causing low photoinduced electron injection efficiency,insufficient driving force of electron injection and the severe recombination of photogenerated carriers;short electronic life of devices,short electron diffusion length and low charge collection efficiency limit the improvement of sollar cells.Therefore,it is urgent to modify the titanium dioxide in more effective ways.At present,the photovoltaic conversion efficiencies of DSSC and PSC based on TiO₂ nanoparticles have reached to 14% and 22%,respectively.However,due to the wide band gap of TiO₂,it is hard to improve the efficiency of solarcells further.The wide band gap reduces the driving force of electron injection.These three demerits of TiO₂ result in the limition of light harvesting in visible and near infrared region as well as the recombination of photogenerated electron/hole in solarcells.To solve these problems,we introduce self-structure modified TiO₂ nanoparticles with hydrogenation thermal treatment.Based on this treatment,pressure/temperature controlled hydrogenated titanium dioxide?H-TiO₂?nanoparticles,hydrogenated F/NF doped TiO₂ composite nanoparticles,hydrogenated nanospheres/nanowires were prepared and applied as photoelectrode materials for DSSC or PSC.Firstly,we studied the hydrogenated TiO₂ prepared in different methods,applied them as photoanode materials in DSSC and deeply studied the mechanism of improved efficiencies.We studied the effects of pressure difference on H-TiO₂.Different hydrogenation pressure produced the H-TiO₂ with varied degrees of agglomeration and crystallization.We used UV-vis spectroscopy,Mott-Schottky,Electron Paramagnetic Resonance?EPR?and Electrochemical Impedance Spectroscopy?EIS?to study their optical and electrical properties.Experimental results showed that the absorption ability of H-TiO₂ nanopowders prepared by atmospheric pressure system was enhanced and the donor density in H-TiO₂ was significantly increased,improving the cell performance.The photoelectric conversion efficiency?PCE?was increased by 17%.On the basis of the controlled pressure,H-TiO₂ nanocrystals with different hydrogenated temperature were successfully prepared and employed as photoanode materials in DSSC.Photoanodes with H-TiO₂ nanocrystals hydrogenated at 300 °C showed the best performance.And the short-circuit current density?Jsc?reached to18.92 mA cm-2 and photoelectrical conversion efficiency was 7.76% under standard AM 1.5 global solar irradiation,indicating a 27% and 28% enhancement in Jsc and ?,respectively.In comparison to those with TiO₂,the enhancements were attributed to the higher donor density?3.53 × 1021 cm-3?,narrower band gap and positive shift of flat band energy?Vfb?of H-TiO₂,which promoted the driving force for electron injection.Secondly,we introduced non-metallic modification to improve light harvesting via the synergistic effect between the non-metallic modification and hydrogenation thermal treatment and studied the H-TiO₂'s effect on typical structure cell and hierarchically structure cells.After hydrogenation,prepared H-TiO₂-xFX nanopowders showed enhanced utilization of visible light,increased donor density,strenghtened driving force of electron injection and improved photoelectric properties of DSSC.The results showed that,compared with the untreated TiO₂-xFX,the photocurrent and the PCE of the H-TiO₂-xFX were increased by about 48% and 36%,respectively.Besides,lotus-like hydrogenated NF-TiO₂ material was prepared and applied as light-scattering layer in DSSC,which broadened the light absorption in the visible and near infrared region and served as the light scattering layer,enhancing the light harvesting efficiency.Also,synergistic interaction between non-metal elements and hydrogenation improved the electron transfer capability and inhibited the photogenerated carriers' recombination,thus improving the photoelectric conversion efficiency.The photocurrent of DSSC based on HNF-TiO₂ nanopowders was increased by 40% and the PCE was enhanced by 38%.Thirdly,we optimized the mesoporous layer of perovskite solar cells by using multi-dimensional hydrogenated titanium dioxide nanomaterials to improve the utilization of visible and near infrared light.We prepared hydrogenated titanium dioxide?H-TiO₂?nanocrystals and nanorods?H-TNR?and applied them in mesoporous layer.The optical absorption capacity,band gap and the change of donor density of TiO₂ were investigated by UV-vis spectroscopy and Mott-Schottky analysis.The experimental results showed that H-TiO₂ had moderate oxygen vacancis,which quenched the electrons in perovskite layer,achieving effective electron extraction and transfer and accelerating the separation of electrons and holes.Mainwhile,the reverse recombinations were surpressed,the electron lifetimes were prolonged and the photoelectric conversion efficiency was improved efficiently.As a result,the photoelectric conversion efficiency of the battery can reach to 13.22%,which was increased by 22% compared with the PSC based on TiO₂ nanocrystals.