Construction Of High Performance Perovskite Solar Cells By Solid Additive Passivation Strategy

Organic-inorganic halide perovskite solar cells（PSCs）have attracted extensive attention in recent years due to their excellent optoelectronic performance and low manufacturing cost.As a light absorption layer,the film quality of perovskite is the most important factor to obtain efficient and stable perovskite solar cells.However,the low temperature solution preparation method commonly used for inverted perovskite photovoltaic devices is far from thermodynamic equilibrium,which leads to the formation of a large number of defects inevitably in the final polycrystalline perovskite film.As a simple and efficient way,additive engineering not only plays an important role in the control of perovskite crystal kinetics,but also effectively passivates perovskite bulk defects,grain boundary and surface defects.Therefore,this paper introduces novel functional organic solid additives into the perovskite active layer to regulate the nucleation and growth of perovskite crystal,reduce the defect state of perovskite film and improve the film quality,thus resulting in remarkable enhancement in both power conversion efficiency（PCE）and device stability.The detailed contents are as follows:（1）The commercial pyridine dicarboxylic acid（PDA）molecule was selected as an efficient passivator to effectively passivate the surface and grain boundary defects of perovskite active layer through the chelation effect between carboxylic acid,pyridine functional groups and perovskites.High quality perovskite films with passivation layer were prepared by introducing PDA molecules with pyridine and carboxylic acid groups on the prepared perovskite films by post-treatment.PDA molecules can not only effectively reduce the grain boundary defects of perovskite films,but also synergistically passivate the uncoordinated Pb²⁺defects in perovskite films,greatly reducing the density of defect states and inhibiting the carrier recombination.The PCE of the device optimized by PDA is increased from 16.49%of the standard device to nearly 19%.Meanwhile,the long-term stability and thermal stability of the optimized device in inert environment are also greatly improved.（2）Fluorophenylboronic acid（F-PBA）was used as a cross-linking agent to repair the defects of perovskite films through the hydrogen bond interaction between F-PBA and perovskite crystals.High quality perovskite films were prepared by introducing F-PBA into perovskite precursor solution by simple doping method.F-PBA can be used as a physical crosslinker to connect the perovskite grains,so as to repair the defects of perovskite films and effectively inhibit carrier recombination.At the same time,F-PBA can improve the crystallinity of perovskite films.Therefore,the PCE of the device doped with F-PBA is greatly improved,and the performance of the optimal device is significantly increased from 16.4%of the standard device to nearly 20%（19.9%）.It is worth mentioning that the physical crosslinking agent can greatly improve the air stability and thermal stability of the device.（3）A dual passivation strategy was proposed,in which trimethylol aminomethane（THAM）was used to effectively passivate the bulk and surface defects of perovskite films.Firstly,THAM was doped into perovskite precursor solution to slow down the nucleation growth rate of perovskite,so as to increase the grain size of perovskite and realize the effective passivation of bulk defects;Then,THAM passivation layer was prepared on the surface of perovskite thin films by spin coating method to passivate the surface defects and finally achieve the dual passivation of the film defects.Compared with the pristine MAPb I₃ film,the MAPb I₃ film with double passivation method has lower density of defect states,and the corresponding device efficiency is further improved.