| Recently,rapid progess in the development of perovskite solar cells(PSCs)has been witnessed,which shows great potential for the commercial applications.The precursor solution properties and the formation mechanism of perovskite thin films become the critical scientific issues to achieve the high-performance perovskite solar cell(PSC)devices.This study focused on the coordination interaction in perovskite precursor solution,and the inherent relation between the precursor solution properties and the quality of perovskite films.The components and size of coordination clusters were controlled by the selective introduction of additives in precursor solution with the aim of achieve controlled growth of perovskite films.In addition,the commercial polyimide tape was applied to improve the stability of perovskite films and devices.The introduction of bidentate ligand additive of 2-aminoethanethiol(2-AET)in perovskite precursor solution leaded to the formation of stable coordination complexes of PbI2ˇ2-AETˇMAI.The bridge link of inorganic component of PbI2 and organic component of MAI avoided the needle-like perovskite crystal,which caused by the preferential precipitation of PbI2 from the conventianal perovskite precursor solution.During the annealing process,2-AET was gradually driven to the grain boundaries,which inceased the interfacial energy and induced the annexation of perovskite grains,the significant preferred oritentaion of(110)and(220)crystal planes were obtained.Finally,the compact perovskite films with equiaxed grain were obtained.Besides,2-AET in the surface and grain boundaries of perovskite could form compact molecule barrier layers to prevent the penetration of water into perovskite structure,the tetragonal perovskite phase retained after immersion in water for more than 10 min at room temperautre.While the migration of charge carriers is limited due to the electrical insulation of organic ligands.In order to improve the quliaty of perovskite film without compromising the charge carrier mobility,the volatile additive of MACl with strong coordination ability was incorporated in perovskite precursor solution.Acoording to the dynamic light scattering spectra,the size of colloidal clusters in standard perovskite precursor solution is about 100 nm,while it increases to 350 nm and 500 nm with the additive of MACl and DMSO+ MAC1,respectively.We confirmed that the size of colloidal clusters in precursor solution was correlated with the size of perovskite grains.As a result,the monolayer-like perovskite films with an average grain size of 3 ?m were obtained based on the colloidal engineering perovskite precursor solution.In addition,compared with the conventianal perovskite thin films,the trap-state density of monolayer-like was lower by an order of magnitude,the produced PSCs showed a PCE of 19.1%.This study confirms that the size of colloidal clusters in precursor solution is correlated with the grain size of produced perovskite films.With the aim of accelerating the nucleation rate of perovskite intermediate phase,the MAPbBr3 with low solubility was introduced as perovskite seed in the precursor solution with additive of MACl.During the nucleation and growth of perovskite crystals process,the preferential crystallization of MAPbBr3 seed would induce the nucleation of perovskite intermediate phase to obtain the compact perovskite films without the employing of anti-solvent.In addition,the Br-doped perovskite films showed improved crystal quality with a carrier lifetime of 324.4 ns.The PSCs based on the thick perovskite film(600 nm)showed a PCE of 18.9%.To improve the long-term of perovskite films and PSCs,this study demonstrated that an adhesive encapsulation by employing the commercial polyimide tape.The encaplustated perovskite films showed an excellent water resistance.There were no visble changes for the encaplustated perovskite films after immersion in water for 3 h,and the outside decomposition products of PbI2 crystals would serve as H2O molecule diffusion barrier layer to protect the inside perovskite crystals.Moreover,the encaplustated perovskite films exhibited a significant thermal stability.The encapsulated perovskite films could retain tetragonal perovskite crystal structure at 240? for 3 h in the ambient environment.For the encapsultated PSCs devices,the stable operation of encapsulated PSCs in water with a PCE of 19.1%was achieved,and the stable power output of device could retain 96.3%of its initial efficiency in water for 1620 s under continuous illumination.We highlight the formed adhesion force between encapsulation films and perovskite films not only retard the diffusion kinetics of water molecule into perovskite structure,but also eliminate the potential diffusion path for the volatilization of the organic component to enhance the thermal stability of perovskite. |
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