Research On Perovskite Film Manufacturing Technology And Hysteresis Suppression

In recent years,climate changes anomaly around the world,extreme weather increases rushly,and energy crisis becomes increasingly serious.Solar energy is a kind of renewable inexhaustible resource.Efficient solar cells could not only relieve the threaten of energy crisis,but also avoid the environmental pollution caused by the traditional fossil fuel.Perovskite solar cell is an emerging and promising star in photovoltaic area.The efficiency has raised rapaidly in last ten years,outweigh that of the silicon solar cell,showing a bright market value.This thesis adapts vaporassisted solution process to deposit perovskite film,and mainly focuses on the improvement of manufacturing procedures.In addition,the hysteresis phenomenon will be numerically discussed to clarify the underlying factors and put forward feasible methods to suppress it.Firstly,chemical vapor deposition process is simulated using FLUENT software,defined by relevant control equations and boundary conditions.The influences of porous media and self-designed quartz tube structure on mass and heat transfer of the vapor MAI are discussed.Moreover,the influences of working temperature and pressure on the uniformity of MAI vapor concentration and perovskite film deposition rate are investigated.And in this simulation,assuming that lead iodide film is good and sufficient to fulfill the perovskite film deposition process,ignoring the surface and grain quality of the perovskite film.The uniformity of MAI vapor distribution and perovskite film are the primary research points.The simulation results could be a useful guideline to make uniform,large area and repeatale perovskite films.The surface morphology and grain quality of lead iodide film,as the precursor film for perovskite deposition,affect the quality of perovskite films.In the ambient air conditions,the influences of relative environmental humidity on coverage and pinhole defects of lead iodide films are studied.The corresponding surface morphology of perovskite films and solar cell efficiency are characterized to clarify the rule of relative environmental humidity on lead iodide film manufacturing technology and the solar cell efficiency.At 16% relative humidity,the best efficiency is 8.55%.In addition,dry air flow is introduced to the lead iodide film manufacturing technology,combining with x ray diffraction and scanning electron microscope test,a supersaturation nucleation and crystallization curve of the lead iodide solution is obtained qualitatively.The influences of dry air flow on lead iodide spinning,drying and annealing process are studied,in order to produce high-quality lead iodide and perovskite films.Combined the dry air flow assisted spinning,drying and annealing in the lead iodide manufacturing technology,the best solar cell efficiency reaches to12.4% at 16% relative humidity.The porous media has serious requirements for material stability and manufacturing technology.A facile sandwich structure is proposed to perform the chemical vapor deposition process,lead iodide substrate sandwiched by the MAI source.The perovskite film deposition is conducted in a minor-caliber quartz tube,without the porous media screen.The uniformity of MAI vapor flow and perovskite film deposition rate are calculated and verified using FLUENT steady and transient simulation.In addition,a passivation interlayer is introduced between the perovskite film and the electron transport layer to suppress the hysteresis phenomenon.The effects of the interlayer on perovskite film surface morphology and grain quality are investigated.The passivation interlayer is supposed to improve the electron transportation and inhibite interfacial defects.With the passivation interlayer,the difference of filling factor between the forward scan and the reverse scan reduces to6%,and the best efficiency is 12.2%.For the notorious hysteresis phenomenon in perovskite solar cells,numerical simulations are performed using COMSOL software based on the working mechanism of perovskite solar cells.Charge carriers and ions movement in perovskite film are defined using drift diffusion model,combined with bulk and surface recombinations.The influences of pre-poling voltage,scan rate and direction,perovskite and transport material parameters on potential profile distribution,electric field and ions concentration are carefully studied.The underlying mechanism and suppression methods to the hysteresis phenomenon are clarified.The innovations and significances of this thesis include:(1)the porous media chemical vapor deposition could guarantee the uniformity of perovskite film.The influences of reaction boundary conditions on the uniformity are simulated and clarified to guide the experiment.(2)In the ambient air atmosphere,the influences of dry air flow on the surface and grain quality of lead iodide and perovskite films are investigated.Combined with the supersaturation nucleation and crystallization,lead iodide and perovskite films with well surface and grain quality are obtained.(3)The hysteretic simulations of perovskite solar cells present the underlying factors and suppression methods to the hysteresis phenomenon,paves the development of perovskite materials.