Study On The Regulation Of Perovskite Defect State And Its Influence On Cells Performance Ang Stability

Organic-inorganic metal halide perovskite materials have become a promising new star in the photovoltaic field due to their excellent photoelectric properties.However,there is still a gap between the current photoelectric conversion efficiency（PCE）and Shockley-Queisser（S-Q）limits,and the poor long-term stability of perovskite solar cells（PSCs）is also a barrier to entry into the commercial photovoltaic market.The packaging method can overcome the stability problems caused by external factors such as moisture and oxygen,but cannot solve the stability problems caused by inherent defects and thermal degradation.Previously,it has been widely proved that,under the working conditions of light and external electric field,the defects in the interior and surface of perovskite can induce ion migration and charge accumulation,thus seriously accelerating the degradation of perovskite.In addition,these defects also trap free charge carriers and subsequently annihilate them with opposite charges by acting as non-radiative recombination centers,which greatly impairs the efficiency of PSCs.Therefore,the passivation of perovskite material defects is the most important prerequisite for obtaining efficient and stable PSCs.（1）Large grain and high quality perovskite films were prepared by adjusting the perovskite crystals with additive methylamine hexafluorphosphate（MAPF₆）ionic liquid.The hydrogen bond between MAPF₆ and perovskite components（FAI）was characterized by Fourier infrared（FTIR）,and the interaction between MAPF₆ and perovskite was further demonstrated by steady-state photoluminescence（PL）.We systematically studied the effects of MAPF₆ on the morphology,trap density,carrier transport and recombination of perovskite films by using carrier dynamics dependent characterization methods.The results show that MAPF₆ can stabilize the lattice structure of perovskite,greatly reduce the trap density of the film,and inhibit the harmful non-radiative recombination.Finally,after MAPF₆ treatment,the PCE of the device increased from 20.77%to 22.45%of the control.（2）We introduced trimethyl sulfoxide iodide（TMSI）as an additive along with tin fluoride（Sn F₂）into tin-lead（Sn-Pb）alloyed perovskite and fabricated Sn-Pb perovskite films with increased grain size and improved film quality.TMSI inhibited the oxidation of Sn²⁺through molecular interactions and reduced the formation of harmful Sn vacancies.The results show that the high orientation Sn-Pb alloy perovskite with low defect density was obtained and the ion migration was inhibited.The TMSI-treated Sn-Pb based devices exhibited a champion PCE of 22.6%and outstanding stability,retaining 83%of their original efficiency after 6000 h of storage under a N₂ atmosphere and maintaining 88%of their initial value after 1200 h of continuous one-sun illumination.