Engineering Research On Defects Of Organic-inorganic Hybrid Perovskite Solar Cells

As a direct bandgap semiconductor with ionic properties,organic-inorganic hybrid perovskite has attracted extensive research attention due to its excellent optoelectronic properties and low cost solution manufacturing.In recent years,based on interface optimization and composition engineering,the power conversion efficiency(PCE)of perovskite solar cells have increased rapidly,and the current world certification efficiency has reached 23.7%.However,a large number of defects at grain boundaries and surfaces of the polycrystalline perovskite films are unavoidable because of low-temperature solution-based preparation processes which are far from thermodynamic equilibrium.The defects at the grain boundaries and surface would unevitably induce the charge carrier recombination and seriously limit the further increase of PCE and stability.The effective passivation of the internal defects has become one of the key factors for the high-quality perovskite films and high-performance solar cells.Therefore,the defect passivation mechanism of perovskite thin films is the core scientific problem in basic research of perovskite field.In this paper,three dimensional(3D)perovskite and RP/3D(Ruddlesden-popper)heterojunction perovskite films were used as the carriers to systematically study the passivation mechanisms within the polycrystalline film,revealing the contribution of defect passivation to charge transport and crystal phase stability,and therefore realizing the perovskite solar cells with leading performance.The specific works are as follows:1.We developed a Lewis acid-base passivation strategy based on organic semiconducting molecules.The model of the passivation mechanism is proposed to understand how the molecules simultaneously passivate the Pb-I antisite defects and vacancies created by under-coordinated Pb atoms.The superior optoelectronic properties and stability are attained by optimizing the molecular passivation treatments.These benefts are translated into signifcant enhancements of the PCE of MAPbI3 solar cells.The insights of this work would provide a new strategy to more effectively passivate the defects within the perovskite films.2.We demonstrated a new strategy through combining the RP/3D heterostructured film with Lewis acid-base passivation.The contribution of bulk heterostructure and lewis acid-base passivation to charge transport and stability of formamidine-based perovskite(FAPbI3)film was revealed.Comprehensive film and device characterizations were performed to understand the correlation of defect passivation,film photoelectric properties and device optoelectronic properties.A stable and efficient device(20.62%)was achieved through this synergistic effect.Our findings provided a new method for the construction of high peroformance organic-inorganic hybrid perovskite3.We reported a RP/3D hierarchy heterostructure through the effects of interface nucleation and templated growth of quantum wells(QWs).The influences of underlying 3D perovksite on nucleation and templated growth mechanism were studied.The interface passivated effect and charge dynamics at the heterojunction were systematically investigated.The control strategy of the band alignment and quantum well orientation was testified its roles in the optoelectronic properties of RP/3D heterostructure.As a result,interface engineering enables the fabrication of high performance FAPbl3-based solar cells.We believe our results would provide a theoretical guidance for the development of new-type hierarchy heterostructure perovskite solar cells.