| As a kind of clean energy,solar energy has extensive utilization value.Photovoltaic power generation is the most promising method during varies of solar energy utilization.In recent years,a new type of perovskite solar cells(PSSCs)has become a research focus due to its low cost,simple preparation and high efficiency(from 3.8% in 2009 to 22.1% in 2017).The challenges of the PSSCs development are as follows: low temperature preparation of porous structure electron transport layer(ETL);design of environmental friendly and stable perovskite materials;preparation of low cost and high efficiency cavity transport layer;industrialization of the PSSCs.In this thesis,we focus on low-temperature preparation of ETL of plane perovskite heterojunction solar cells,and modify this layer to improve the performance.Furthermore,PSSCs without use of lead are also studied to develop a new type of environmental friendly solar cells.The main contents are summarized as following.To study the low temperature preparation process of ETL,a laser annealing method is used to prepare the film of tin oxide(Sn O2).Using Sn Cl4 solution as the precursor,water as the diluent solvent,the films are prepared by Spin-coating method,and the crystalline Sn O2 films are obtained after laser annealing.The results show that with the increase of the laser annealing time,the crystallinity of Sn O2 thin film become better,and the best crystallinity appears at 20 ms.The Cl element on the surface is analyzed by X-ray Photoelectron Spectroscopy(XPS)to determine the Sn Cl4 completely transform into Sn O2.Scanning Electron Microscope(SEM)show uniform Sn O2 layer formed on the surface of the FTO.Laser annealing method realizes the preparation of ETL at room temperature in a short time of 20 ms.After assembling titanium solar cell using this ETL,the photoelectric conversion efficiency reaches to 15.27%.In the modification resarch of the ETL of the PSSCs,the primary modifying material is graphene.Using graphene oxide(GO)and titanium tetraisopropanolate(TTIP)as the precursor solution,through the hydrothermal method for synthesis of graphene doped titanium dioxide(Ti O2).Then prepare the slurry,using screen printing method to prepare the titanium dioxide(Ti O2)electronic transport layer film which have been studied in dye sensitized solar cell(DSSC),the experimental results show that the graphene modification of Ti O2 thin film exhibits a higher battery efficiency than the pure Ti O2.In another work,Sn Cl2 ethanol solution and graphene/EC solution are employed as the precursor for spin coating to prepare the graphene modified Sn O2 films.When using this ETL to fabricate the planar heterojunction PSSCs,the efficiency of the battery increases from 15.23% to 16.67% after the addition of graphene,and the open voltage also increase s from 1.06 V to 1.1V.The mainly reason is that the graphene possess high electron transport characteristics which can accelerate electron transfer and then improve the performance of the device.In the study of graphene modified Sn O2 based battery,its stability is noticed to be improved by chance.After 10 days of preservation in ambient condition,the graphene modified Sn O2 based battery maintains an efficiency of 80% compared to that of nearly 0% of the pure Sn O2 film based solar cell.This unexpected discovery has led to a new direction in the stability of the PSSCs.1/f noise analysis for perovskite solar cells in light and dark conditions were studies.We collected noise data with two different preparation method of perovskite device,one step and two step.A simple characteristics model of device stability and reliability was obtained by fitting these experimental data.In conclusion,it is a linear relationship between the noise frequency(Log SI)of perovskite solar cells in dark condition and the current generated inside the battery,suggesting that the battery in dark condition is more stable;a non-linear relation can be found between the Log(SI)and Log(I)in light condition,suggesting that the electrons inside the battery with a poor stability are active.In order to solve the problems of the environmental friendly and stability of the Pb based solar cells,we select Se(Selenium),an environmental friendly light absorbing material,as a substitute for photon absorption layer of perovskite materials in PSSCs,and successfully prepare Se film in solution process for the first time.To prepare Se crystal film,elemental selenium powder is the raw material,and hydrazine is chosen as the solvent,and then add some ethylenediamine(EDA)to promote the formation of the film.Einally,the film is calcined at 200℃tfor 3 min.When fabricating device using this Se film,photoelectric conversion efficiency reaches to 3.52%,and maintain a certain efficiency after being kept in air condition for one year.It provides a new route for developing lead-free device and environmental friendly device with high stability. |
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