Preparation And Optimization Of Perovskite Films And Their Solar Cells Performance

Since CH₃NH₃PbI₃ has been reported as light-absorbing material of solar cell in 2009,perovskite solar cells have made rapid progress,also theoretical exploration and preparation process have been developed by leaps and bounds.How to achieve further leap to speed up the process of industrialization of perovskite solar cells,there are many scientific issues to be solved,in which the preparation process of high-quality perovskite films is particularly important.In order to solve the existing problems,this paper studied the scientific researches on crystal growth of perovskite films,energy level regulation of materials,structure design ofperovskite films and development of largearea devices.The effects of conditions of preparation andoptimization on the photovoltaic properities of perovskite films were studied by means of preparation of the materials,characterization of performance and structure,design and assembly of devices and evaluation of efficiency.Also,scientific laws such as electron transfer kinetics,interfacial matching,energy matching and structure matching of the perovskite films were further studied.And the main research contents and results are as follows:?1?A three-step sequential coating method was developed to prepare high-quality perovskite films by isopropanol solvent engineering.Stonehenge-like PbI2 nanostructures with controllable morphology and crystallinity were prepared by solvent substitution instead of the conventional annealing-treatment,affording several channels for CH₃NH₃ I to penetrate into the PbI2 film due to volume expansion,thus enabling the complete conversion from PbI2 to perovskite.In addition,the devices exhibited high reproducibility by our method and achieved a high 17.78% power conversion efficiency under one-sun illumination.?2?Based on the solvent bathing method and the concept of solvent extraction,we put forward a method to prepare high quality perovskite films by using environmentally friendly alcohol solvent bathing,avoiding the use of toxic solvent.The growth mechanism of perovskite films in different solvents bathing was studied,and the effects of solvent bathing method on the photovoltaic performance and the mechanism of electron transfer kinetics were studied.?3?We increased the DMSO content in the Lewis acid-base adduct approach to enhance the conversion efficiency of perovskite solar cells.More complete intermediate adduct CH₃NH₃I·PbI2·DMSO and wider window period of washing process ensured high-quality perovskite films and high reproducibility with raised content of DMSO.?4?The growth mechanism of hybrid perovskite?CH₃NH₃PbI3-xBrx?films was studied.The effect of CH₃NH₃ Br on the perovskite film was investigated by controlling the doping ratio of bromine substitute for iodine.The band structure of perovskite materials and the microscopic mechanism of electron transport kinetics in perovskite solar cells were further illustrated,resulting in the significant improvement of photovoltaic performance of PSCs.?5?Through the design of functionally graded structure,the Spiro-OMeTAD hole-transporting material was dispersed in perovskite film in gradient structure.Also,the gradient structure was proved by the EDX mapping and SIMS.The dynamics of carrier transport and the mechanism of gradient structure were further analyzed.?6?Large-area perovskite solar cells were prepared by Lewis acid-base adduct approach and n-butyl alcohol solvent bathing,the photoelectric properties of large-area perovskite solar cells were compared to study the usability of the two methods in different physical dimensions.Lewis acid-base adduct approach was only suitable for the preparation of small area perovskite solar cell;n-butanol solvent bathing method could be used to prepare large-area high-quality perovskite films,the prepared 10×10 cm2 perovskite film hasperfect mirror effect.