Study On Perovskite Solar Cell Based On The Design Of Two-dimensional Perovskite Interface Passivation Layer

As a new photovoltaic technology,the certified efficiency of organic-inorganic halide perovskite solar cells（PSCs）have risen from 3.8%to 25.5%,which shows the huge application prospect.However,the long-time stability is still one of the most challenging issues need to solve before extreme commercialization of PSCs.The presence of defects in perovskites is one of the main sources of instability.It has reported that grain boundaries of the perovskite films are the initial sites of degradation owing to traps-assisted non-radiative recombination,which seriously influence effective and stability of PSCs.Recently,two-dimensional（2D）perovskite has been appeared to researchers on account of the outstanding stability.Therefore,we designed and studied 2D perovskite passivation layer to improve the performance of 3D perovskite film and devices,as following two works:Fristly,we studied the 2D perovskite passivation layer with high dipole moment on performance of perovskite solar cells.By the means of introducing 2,2,2-trifluoroethylamine hydroiodide（FEAI）with a high dipole moment to grow a 2D perovskite layer at the interface between 3D perovskite absorber layer and hole transport layer（HTL）.We studied the effect of FEAI in different concentrations on crystallization,surface morphology and carrier dynamics of PSCs,leading to higher photovoltaic performance with suppressed non-radiative recombination.Moreover,owing to the passivation and protection effects of the（FEA）₂Pb I₄modified layer,the modified devices display superior moisture stability compared to the control devices.Then,we focused on the effect of 2D perovskite passivation layer with poly-functional groups on 3D perovskite performance,and firstly introduced L-cysteine methyl ester hydrochloride（CME）at the interface of perovskite/HTL to grow the 2D perovskite layer.It uses the functional groups of thiol（-SH）,ammonium salt（-NH₃⁺）,and ester（-COO^-）in organic compound to enhance coordination between the ammonium salt group（-NH₃⁺）and[Pb I₆]^4-octahedron framework.Due to the excellent hydrophobicity of-SH,the 2D passivation layer could effectively prevent moisture from penetrating into the perovskite interior.The 2D perovskite layer could optimize interface and suppress charge non-radiative recombination induced by defects,which as a result of high efficiency and outstanding stability.In conclusion,we have improved the performance of 3D perovskite film by 2D perovskite layer based on different ammonium salt.And the influence mechanism of the different chemical properties and structures of organic ammonium salts on the passivation effect of 2D perovskites has been established,which has further promoted the development of 2D/3D perovskites.