Research On Defect Passivation And Interface Regulation For High Performance Perovskite Solar Cells

As a new photovoltaic material,organic-inorganic hybrid perovskite material has become a research hotspot in the field of optoelectronics due to its excellent properties of high absorption coefficient,low exciton binding energy and adjustable band gap.In just over a decade,the power conversion efficiency of perovskite solar cells has soared from 3.8%to 25.7%,and their huge development potential has shaken the status of silicon-based solar cells.Thus,perovskite solar cells are regarded as the most promising new generation of photovoltaic technology.However,perovskite films prepared by solution processing have abundant inherent defects,which not only cause serious non-radiative recombination,but also accelerate the degradation of perovskite as the sites for water and oxygen invasion.In addition,the energy loss caused by energy levels mismatch between interfaces further restricts the device efficiency to the theoretical limit.Therefore,the aim of this thesis is to promote the commercialization of perovskite solar cells,focusing on defect passivation and interface modification,to study the carrier transport and recombination dynamics in-depth,and further improve the efficiency and stability of devices.The specific research contents are as follows:（1）A small molecule material N,N’-DIALLYL-L-TARTARDIAMIDE（NDT）is introduced,and the significant improvement of efficiency as well as excellent stability of devices are achieved via additive engineering.It is found that abundant hydrogen bonds are formed between NDT and perovskite,and the carbonyl group of NDT can interact with the uncoordinated Pb²⁺of perovskite.The combination of hydrogen bond and coordination bond can effectively reduce the defect density,greatly inhibit the defect-induced non-radiative recombination,and stabilize the crystal structure of perovskite.In addition,NDT can improve the electrical conductivity of perovskite films and then promote the carrier transport at the interface.As a result,the device achieves a high efficiency of 21.7%,and the unpackaged device maintains over 95%of its initial efficiency after 2500 h storage under ambient air with 45%relative humidity.（2）A"three birds with one stone"strategy is proposed,in which Daminozide（DA）is used as an interface layer and an additive to synchronously regulate the energy levels at the buried interface and passivate the defects at such buried interface as well as in the perovskite film.The successful construction of PTAA:F4TCNQ/DA/perovskite:DA heterojunction promotes extraction and collection of carriers at the hole contact interface and effectively inhibits the interface recombination.In addition,the growth of perovskite crystal is regulated by DA molecules,and the increase of grain size,together with the coordination and hydrogen bonding between perovskite and DA,passivate the defects at the buried interface and in the bulk of perovskite,enhance the lattice stability of perovskite.Consequently,the stability of the device is improved significantly,and the efficiency of 22.15%and the fill factor of 83.92%are achieved,both values are the highest records for polycrystalline MAPb I₃ inverted perovskite solar cells reported to date.