Study On Application Of Two-dimensional Layered Structure In Perovskite Solar Cells

Perovskite solar cells（PSCs）using traditional three-dimensional（3D）halide hybrid perovskites have attracted tremendous attention and become a hot spot in the photovoltaic device field.3D perovskites usually have preeminent photoelectric properties due to the favorable electronic band structure with broad conduction and valence bands.In recent years,the power conversion efficiency（PCE）of typical 3D organic-inorganic halide perovskite-based solar cell has got a rapid growth from only3.8%to a certified 25.7%,which could be put on a par with silicon-based solar cells.However,the long-term intrinsic instability of PSCs limits their future commercialization.For example,MA⁺-based perovskites（MAPbI₃）are apt to degrade under high temperature and moisture,FA⁺-based perovskites（FAPbI₃）have a problem of phase instability,and the all-inorganic Cs⁺-based perovskites（CsPbI₃）are also faced with the issue of phase instability.During the past several years,researchers have paid much attention to ameliorating the long-term stability of PSCs.Various avenues have been employed to improve the stability of PSC devices,including defect passivation,morphology modification,phase stabilization,component engineering,and additive control.Moreover,using two-dimensional（2D）as an efficacious category has also exhibited great latent capacity for perfecting the stability of PSCs.The 2D perovskites exhibit excellent structural diversity,and their properties can be tuned by the spacer cations.The introduction of 2D perovskites into 3D counterparts has attracted more and more attention.2D perovskites has become a common choice for durable PSC due to its outstanding stability,especially excellent moisture resistance.Here,we mainly focus on the effect of two-dimensional structure on the stability of perovskite solar cells,including the following parts:Highly efficient and stable quasi-two-dimensional（quasi-2D）hybrid perovskite solar cells using super hydrophobic 4-（trifluoromethyl）benzylamine（4TFBZA）as the spacer cation are successfully demonstrated.It is found that the incorporation of hydrophobic 4TFBZA can effectively induce spontaneous upper gradient 2D（SUG-2D）structure,passivate the trap states and restrain the ion motion.Meanwhile,the strong hydrogen bonding of F···H‐N between 4TFBZA ion and methylamine ion can effectively suppress the decomposition of perovskite,which gives the device a better thermal stability.Besides,due to the SUG-2D structure with hydrophobic4TFBZA,the device also exhibits a better moisture stability.The SUG-2D based device exhibits a power conversion efficiency of 17.07%with a high open-circuit voltage of 1.10 V and a notable fill factor of 71%.This work provides a new strategy for constructing efficient and stable quasi-2D PSCs,and it is an inspiration for the packaging strategy of perovskite.By forming dual low-dimensional perovskite structure,an efficient hole extraction from bulk perovskite to the surface layer,and a reduced interface non-radiative recombination from the bottom layer to bulk perovskite can be accomplished in unison.The 2D/3D/2D structure further facilitates charge transfer in the complete device through improved energy level alignment,and stabilizes the perovskite interface and lattice through suppressed ion migration,thereby leading to the increased V_OC.The perovskite device with 2D layer yielded a PCE exceeding21.57%（stabilized efficiency of 20.7%）with negligible hysteresis.Owing to the improved stability of the perovskite material itself and the passivated crystal defects,the 2D/3D/2D PSCs exhibited superior long-term stability against humidity and high temperature.This finding provides an effective strategy to manage Pb-based defects at the interface for achieving the manufacture of high-efficiency and stable perovskite photovoltaic devices in practical applications.