Research On Optimization And Modification Of The Light-absorbing Layer Of Perovskite Solar Cell

As the increase of demand for clean sustainable energy with the development of our modern life,the exploration of new active materials for energy conversion and energy-storage devices have appealed great attention of researchers.Among them,organic-inorganic hybrid metal halide perovskite compounds become the most concerned photovoltaic star materials due to their high absorption coefficient,tunable band gap,long carrier lifetime,low binding energy,etc.The power conversion efficiency(PCE)of the perovskite solar cells(PSCs)increased from 3.8%to 25.2%within decade,rapidly.However,as the core of the perovskite solar cells,the film quality of the active layer largely decide the performance of the devices.It is easy to form many defects such as vacancy,antisite,uncorrdiate for thin films of perovskite absorption layer prepared by sol-gel method in the annealing process,resulting in relatively small grain size with a large number of grain boundaries,and serious carrier recombination.In this paper,aiming at the problems such as the undesired morphology,small grain size and ionic defects in perovskite film,doping and pre-deposition were studied to improve the film morphology of perovskite absorption layer,which increased the grain size,reduced ionic defects,and synchronously improved the efficiency and stability of the PSCs.The main research contents and results of this paper are as follows:(1)Traditional organic hole materials are not only expensive but also have poor stability,which is not conducive to the long-term improvement of the PSCs.Therefore,CuSCN,an inorganic p-type material with low cost and good stability,was used as the hole transportation material(HTM)and introduced into the perovskite absorption layer.The results show that the addition of CuSCN is beneficial to passivate ion defects,improves the film morphology,increases the grain size and reduces carrier recombination.The power conversion efficiency and stability of the devices have been effectively improved.(2)The quality of perovskite films is not only influenced by the processing technology and environment,but also closely related to the morphology and quality of the underlying films.In order to improve the quality of the perovskite film deposition and compensate of the insufficient of the organic cations during the annealing process,in this chapter,pre-deposition of MACl solution was used to enhance the crystallinity of the perovskite film,to reduce the crystal defects.Results show that grain distribution is more uniform and dense,the carrier transportation between electronic transport layer and absorber layer was improved.At the end,the optimized device efficiency improved by nearly 1 1.4%compared to the control group.(3)Because of the low binding energy and its ionic nature,the perovskite layer is prone to produce various ionic defects during the film forming process.In addition,due to extremely sensitive to humidity of perovskite layer,water will accelerate the decomposition of perovskite film,resulting in a rapid decrease in efficiency and stability of the PSCs.In this paper,a multifunctional surfactant,hexadecyl trimethylammonium bromide(CTAB),was introduced to passivate the ionic defects of perovskite and improve the humidity stability by utilizing the excellent hydrophobic properties of long alkyl chains.The results show that a moderate of CTAB additive in perovskite precursor solution significantly reduced the defects density,inhibited the carrier recombination,improved the film’s hydrophobic performance,and significantly improved the efficiency and stability of the PSCs.