Passivation Of Defects At The Interface Of Perovskite Solar Cells

The main sources of charge recombination loss in perovskite solar cells（Perovskite solar cells;PSCs）are defects and interfaces.Usually,the main functional layer of perovskite thin film battery is prepared by spin coating layer by layer by solution method.In the crystallization process of perovskite thin film layer,the defects of high density appear on the surface of perovskite thin film and along the interfacial grain boundary due to the imperfect lattice arrangement and atomic period disturbance.Such defects trap photocarriers during device operation,reduce the photogenerated current,and lead to energy level mismatches between the active and charge transport layers of the PSCs,limiting the maximum cell voltage available and ultimately reducing the Power convert efficiency（PCE）of devices.In order to improve the film quality of the perovskite active layer and reduce the defect density,an interface passivation layer was introduced to passivate these defects,reduce the non-radiative recombination and stabilize the structure of perovskite.In addition,the electron mobility of the Sn O₂ electron transport layer is lower than that of the perovskite photoabsorption layer,resulting in charge accumulation at the transport layer/perovskite interface,showing serious hysteresis.In order to reduce the charge accumulation at the interface,materials such as C₃N₄ and epoxy resin are introduced to promote the charge collection,so as to improve the conductivity of the electron transport layer.In this paper,we implement the above ideas through concrete measures.1.In this study,functionalized graphene-like materials（C₃N₄）were introduced into the Sn O₂/perovskite interface,and the defects in the Sn O₂ interface were compensated by C₃N₄ to enhance the charge extraction and transfer ability of the electron transport layer.As an insertion layer,C₃N₄ enhanced the surface affinity between Sn O₂ and perovskite,improved the surface spreading of the perovskite precursor solution,helped to improve the film forming quality of perovskite,reduced the intrinsic defects of perovskite to a certain extent,and reduced the non-radiative recombination of traps in PSCs.The efficiency of the device with insertion layer is 19.22%,and the open-circuit voltage is 1.08V.These results provide a promising method for selecting functional layer additives to improve the efficiency and stability of PSCs.2.We are committed to studying the applicability and intrinsic mechanism of epoxy-like molecules in perovskite solar cell packaging.We choose to spin coat a layer of 3,3,3-trifluoro-1,2-epoxypropane on the surface of perovskite films with different components.By studying the structure and performance changes of perovskite films,the interaction of TE on different perovskite surfaces was explored,and then the potential influence of epoxy resin on different perovskite solar cells in cell packaging was evaluated.The results show that TE can react with formamidine cationic perovskite film without damaging the perovskite active layer.As for the methylamine cationic perovskite film,the addition ring-opening reaction between the nitrogen atom and the epoxy group destroys its structure,resulting in a large number of defects.Thus,TE molecule has a protective effect on"diamine"-methylamidine perovskites,while it is potentially destructive to"monoamine"-methylamine perovskites.Through the performance of perovskite solar cells,we found that the molecule can not only improve the long-term stability of"bisamine"perovskite cells,but also make up for the interface defects and improve the performance of perovskite devices.After 30 days,the PSCs maintained 90%of the initial PCE and was more stable than the control device without rotating coated TE.This idea provides us with a new material to improve the performance of perovskite.3.The polymer crosslinking agent molecular ethylene glycol diglycidyl ether（EGDE）was rotated on the surface of perovskite film to investigate the effect of crosslinking agent on the perovskite interface.We chose a strategy using long chain polymers to form macromolecular mesophases to form polymer-perovskite composite crosslinking agent on the surface of perovskite.The results show that EGDE can not only enhance the interfacial charge transfer ability of perovskite,but also form a protective layer on the surface of perovskite,improving the environmental stability of perovskite.