Study On Doping Effect Of Rare Earth Ions In Mesoporous Perovskite Solar Cells

With the rapid development of the economic and social of our nation,energy crisis and environmental pollution are two major problems facing humanity at present.The massive consumption of fossil energy has brought about environmental pollution and energy shortage crisis in today's society.It is imperative to find new energy sources as substitutes for fossil energy.Solar energy,as a new clean and sustainable energy,has attracted wide attention from scientists.In the utilization of solar energy,solar cells are more rapidly developed.Since solid-state organic-inorganic hybrid perovskite materials?CH3NH3Pb X3,X=Cl,Br,I?were reported as solar cell absorbing materials in2009,as a new generation of solar cells,perovskite solar cells?PSCs?have made rapid progress,and its certified photoelectric conversion efficiency?PCE?has soared from 3.8%in 2009 to 25.2%in 2020,which is greatly attributed to the optimized chemical composition of perovskite and deposition processes;optimized metal contacts;interfacial modification and energy level alignment.To further take the step into the commercialization of perovskite solar cells,there are still scientific problems to be solved.In this paper,optimization experiments are carried out on perovskite absorption layer spectral response range,film quality,mesoporous skeleton layer and interface contact.Through the synthesis of mesoporous materials,structural characterization,device structure design and assembly,and photoelectric conversion efficiency evaluation,the effects of doping of rare earth ions and the introduction of their luminescence effects on the photovoltaic performance of mesoporous perovskite solar cell devices are further studied.Good progress has been made through researching the scientific laws of carrier transport dynamics,defect passivation and energy level structure matching in PSCs.The main work of this thesis can be summarized as follows:?1?Application of?-Na YF₄:Yb³⁺/Er³⁺/Sc³⁺@Na YF₄ upconversion luminescent nanomaterials in PSCs.Up-conversion Na YF₄:Yb³⁺/Er³⁺nanoparticles?UCNPs?with uniform size and good dispersibility were synthesized by oleic acid-assisted thermal decomposition method.Sc³⁺ion doping and homogenous inert shell coating were used to further enhance the luminescence intensity and regulation of the luminescent band.The introduction of upconversion materials as spectral converter into photovoltaic devices to harvest and convert near infrared photons to visible photons that can thus be absorbed by perovskite layer and thus the photovoltaic device exhibits excellent performance in the visible and near-infrared regions of the solar spectrum.After optimization,the PCE value of PSC is as high as 20.19%,increased by 15.77%compared with the PSC with traditional commercial mesoporous TiO₂?17.44%?,including the upconversion?UC?contribution about 11.98%.(Sc³⁺:4.31%,Yb³⁺and Er³⁺:7.67%),and the scattering effect contributes about 2.24%.After storage for400 h at room temperature of 40%humidity,it still remained 72%of the highest PCE,showing a considerable stability and a promising commercialization potential.?2?Brookite TiO₂ as a low-temperature solution-processed mesoporous scaffold for PSCs.In order to shorten the preparation cycle and reduce the production cost,binder-free,brookite TiO₂ mesoporous material was synthesized and film-formed at low temperature?150??for PSCs,providing a basis for large-scale preparation of PSCs and flexible PSCs.Furthermore,the electron injection efficiency was improved by doping rare earth ion Sc³⁺into the scaffold to passivate the defect and adjust the energy level structure and optimize the interface contact between ETL and perovskite layer.As a result,we produce a PSC with a PCE of 21.75%which is 10%above that of a device based on planar SnO₂ ETL?19.81%?.Apart from enhancing the photovoltaic performance,the UV stability of PSCs based on SnO₂/Sc³⁺tailored brookite TiO₂ heterogeneous ETL is strikingly improved compared with planar anatase TiO₂ ETL,retaining 86.6%of their initial PCE after 50 h exposure to the UV light,appealing a novel strategy for developing efficient,low-cost and UV stable heterogeneous mesoporous ETL based PSCs.?3?Application of self-assembled SnO₂ mesoporous nanomaterials with UV stability in PSCs.Compared with TiO₂,SnO₂ has emerged as an especially promising candidate possessing optical transparency,low photocatalytic activity,high electron mobility and considerable energy level with perovskite material.SnO₂ based electron transporting layer?ETL?has been well investigated as the substitute electron transporting materials for TiO₂.However,the performance of PSCs based on full SnO₂ mesoporous structure so far has not been in the same league as that of TiO₂ based PSCs.In this work,self-assembled SnO₂ mesoporous materials with high carrier mobility and good UV stability were synthesized by hydrothermal method,and further doped with rare earth ions(Sc³⁺,Y³⁺,La³⁺).Suitable concentration of Ln³⁺dopants optimize the energy level alignment with perovskite layer and significantly heal the charge trap states.Compared with the PCE of the SnO₂-based planar structure PSC?17.21%?,the PCE of the PSC integrated with self-assembled SnO₂ mesoporous scaffold increased to 19.01%?i.e.an increase of 10.46%?.Further surveys show that doping of 3%molar ratio of Ln³⁺can improve the efficiency of mesoporous SnO₂ cells,and 3%-Y³⁺doping can optimize cell efficiency to 20.63%,further increased by 8.52%.Furthermore,the optimized full SnO₂ mesoporous structure PSCs exhibit superior stability after 400 hours of full solar spectrum illumination,remaining 75.8%of the highest PCE,appealing a novel strategy for developing efficient and low-cost full SnO₂ based PSCs.