Study On Lattice Strain Regulation Of Perovskite Solar Cells Fabricated By Blade Coating Method

The organic-inorganic hybrid halide perovskites have emerged as an excellent photovoltaic material.Photovoltaic performance based on perovskites have experienced an unprecedented rise and reached to a certified record power conversion efficiency of 25.5%,which surpasses all other thin film cells.High throughput fabrication of highquality perovskite films becomes a key to commercialize perovskite solar cells.Nevertheless,the residual lattice stress in the perovskite film during thermal annealing process leads to unstable crystal structure and limited charge transport.Herein,this thesis demonstrates effective strategies to reduce the lattice stress/strain for the printed perovskite film via additive engineering,which enables achieve full-printable highefficiency perovskite solar cells under ambient air.1.We demonstrate control of lattice stress by introducing methylamine bromide additive to improve carrier transport within printed MAPbI3-based perovskite layer.We found the key role of the substrate temperature on the fluidity and wettability of the highviscosity perovskite precursor solution on the substrate.A flat and uniform perovskite film was obtained by regulating fluidity.The residual lattice stress of the perovskite film during thermal annealing was further decreased with addition of methylamine bromide additive,which diminishes the formation of inter-lattice defect states and effectively enhances the charge transport of the perovskite film.As a result,the fully printable solar cell based on the eco-friendly printed perovskite film achieves an efficiency of 20.21%（average efficiency of 19.27%）,which is comparable to the efficiency of the traditional solar cell prepared by the small-area spin-coating from toxic solvents.This work is devoted to understanding the relationship between perovskite lattice strain and charge transport,and paves the way to eco-friendly printing of perovskite solar cells.2.We demonstrate control of lattice stress by introducing methylamine bromide additive to improve structural stability of printed FAPbI3-based perovskite layer.We found that the α-phase FAPbI3 crystal can be effectively stabilized with addition of ionic liquid,which interacts strongly with the inorganic framework to release the residual stress of the crystal lattice.This helps realize fully printable FAPbI3-based perovskite solar cells in ambient air with an efficiency of up to 22%.This efficiency also stands as the highest among all FAPbI3 perovskite solar cells fabricated under ambient conditions.This work paves the way to fabrication of stable and high-efficiency perovskite solar cells.