Fabrication Of Efficient And Stable CsPbX₃（X=Br,I） Perovskite Solar Cells Via Thermal Evaporation Technique

The rise of perovskite solar cells（PSCs）provides a new solution for mankind to achieve more efficient use of solar energy.Although the power conversion efficiency（PCE）of organic-inorganic hybrid perovskite solar cells keeps hitting new highs,its instability under high light intensity and high heat restricts its application and development.In this context,the inorganic perovskite material CsPbX₃（X=Cl,Br,I）with better light and thermal stability has received extensive attention.At present,the fabrication of PSCs based on spin coating technique has been fully researched.However,the research based on vacuum evaporation technology,which is more widely used in industrial production,is far from enough.In this paper,based on the sequential evaporation technique and two-step sintering method,we optimize the critical process parameters and perovskite light absorbing layer,thus improving the performance of thermally evaporated CsPbX₃ PSCs and fabricating functional PSCs for specific application scenarios.In general,the main results are listed as following:1.We fabricated CsPbBr₃ perovskite films through sequential evaporation technique and two-step sintering method.By optimizing the parameters of evaporation and sintering process,the crystallinity and morphology of perovskite films were significantly enhanced,and the resistance of charge transmission between layers was reduced.Finally,an all-inorganic PSC based on the FTO/SnO₂/CsPbBr₃/Carbon structure achieved an efficiency of 9.41%and an open circuit voltage(V_oc)of 1.467 V.In addition,the unencapsulated device retained 95%of its initial efficiency after aging at 100℃ for 90 days,which shows excellent thermal stability.To further reduce the trap density of thermally evaporated CsPbBr₃perovskite films and the open-circuit voltage loss of CsPbBr₃ PSCs,we incorporated Ba I₂ additive into CsPbBr₃ perovskite based on sequential evaporation technique.It is found that Ba²⁺ions can enter the CsPbBr₃ perovskite lattice,while I^-ions induced iodine vacancies during the annealing process,both leading to the passivation of CsPbBr₃ perovskite defects and the modification of Fermi level.By adjusting the thickness of Ba I₂ additive,we improved the efficiency of the all-inorganic perovskite solar cell based on the FTO/SnO₂/CsPbBr₃/Carbon structure to 10.09%and the V_octo 1.551 V.In addition,the unencapsulated device retained 93%of its initial efficiency after aging at 100℃ for 90 days.2.By optimizing the process parameters of thermal evaporation,we successfully obtained CsPbBr₃ perovskite film with excellent performance,and then we explored the application of CsPbBr₃ perovskite in semitransparent solar cells.We selected Spiro-OMeTAD as the hole transport material,and compared the transmittance,photovoltaic properties and stability of the semitransparent CsPbBr₃ perovskite with MoO₃/Au/MoO₃ and ITO as transparent electrodes,respectively.3.In order to improve the phase stability of CsPbI₂Br,we explored the effects of Ba²⁺doping,replacement of a hydrophobic hole transport layer,and secondary annealing after phase transformation on the phase stability and device performance of PSCs.