| In the context of China’s all-out efforts to promote carbon peaking and carbon neutrality,it is of great significance to accelerate the construction of a new energy system,increase the proportion of clean energy consumption with solar energy as the mainstay,and promote further breakthroughs in the form of photoelectric energy conversion technology for the efficient use of solar energy.In recent years,due to its unique electronic structure,metal halide perovskite materials with a sixcoordination structure have shown many basic scientific advantages such as high absorption coefficient,tuneable band gap,and high theoretical efficiency limit.At the same time,the low-temperature solution-based techiniques of perovskites makes it possess engineering advantages such as low material cost,low manufacturing energy consumption,and significantly shortened industrial chain.It is considered to be the next-generation photovoltaic technology with the most commercial application prospects.However,the complex bottlenecks such as nonradiative recombination,ion migration in grain boundaries,and energy level mismatch induced by the defects within the perovskite active layer and at the interface between perovskite/charge transport layer seriously restrict the device’s photovoltaic performance and stability,further hindering the commercialization process.Based on this,this paper focuses on the such bottleneck issues induced by complex defect states in perovskite solar cells.Starting from the perspective of improving perovskite crystal quality and optimizing interface,a series of additive engineering and interface engineering strategies have been developed.The growth kinetics and service evolution behavior of perovskites have been explored through several high spatiotemporal resolution in-situ characterization techniques.Also,the defect passivation effect and related mechanism have been revealed,the regulatory mechanism of defect passivation on the charge carrier extraction,recombination,and transport in perovskites have been elucidated,achieving a breakthrough in the comprehensive performance of perovskite-based photovoltaic devices.For the control of crystal quality of metal halide perovskite materials,a series of sulfur donor Lewis base additives have been developed from the perspective of growth kinetics manipulation.The strong coordination interaction between lone pair electrons on sulfur atoms and perovskite precursors has induced the formation of additional Lewis acid-base adduct intermediate phase,thereby delaying the transformation from intermediate phase to crystalline perovskite phase and slowing down the perovskite growth process.Meanwhile,in-situ temperature-dependent measurements have been used to track manipulated growth pathway and phase evolution modulated by Lewis base additives.The inherent mechanism of retardant growth kinetics induced by Lewis base treatment have also been unraveled by means of spectra characterizations together with theoretical calculations.As a result,the significantly reduced trap states and ameliorative carrier behavior dynamics in high-crystallinity perovskite film have been obtained.The electrical parameters of photovoltaic devices based on such high-quality hybrid perovskite thin films have been improved,and an efficiency of 21.45%has been achieved,which can still maintain 91%of the initial efficiency after 720 hours.From the perspective of defect passivation,a composition control strategy based on alkali metal rubidium cation(Rb+)additives has been developed.Grain boundary-included theoretical atomic models have been adopted for elucidate the concentration-dependent Rb+location in perovskites,which has been confirmed by crystal structure information derived from grazing incidence X-ray diffraction technique.On this basis,the passivation effect and mechanism of Rb+doping concentration on defects at grain boundaries and in grain interiors have been clarified.The density of defect states was reduced,effectively improving the carrier dynamics behavior.And it revealed the inhibitory effect of Rb+doping on the ion migration behavior dominated by halide vacancy defects,the dark current at grain boundaries caused by ion migration significantly decreased,and the activation energy of ion migration increased from 0.451 eV to 0.579 eV.Therefore,the critical role of Rb+doping on inhibiting halide phase segregation,and eventually improving intrinsic stability has been elucidated.Aiming at the optimization of buried interface of perovskite solar cells,an interface engineering strategy based on 3-sulfopropyl acrylate potassium salt(SPA)ionic liquid has been proposed.The coordination interaction between the characteristic functional groups on the SPA molecule and undercoordinated metal ions as well as the electrostatic coupling between K+and halide ions has been revealed,endowing the effective passivation of oxygen vacancy defects,undercoordinated Pb2+defects and iodine vacancy defects at the buried interface,which suppressed the energy loss caused by non-radiative recombination.On the other hand,the effect of SPA ionic liquids on the energy band structure has been clarified.It can be clearly seen that the work function of ETL reduced after SPA modification,which leads to well-matched energy alignment between the TiO2 and CsPbI3 perovskite,thereby reducing the electron transfer barrier,providing more effective interfacial charge extraction,and eliminating interfacial charge accumulation.Benefiting from the synergistic advantages brought by buried interface optimization,the champion CsPbI3 solar cells exhibited a record-breaking low VOC deficit of 0.451 V,delivering an extraordinary PCE of 20.98%.Aiming at the optimization of the top interface of perovskite solar cells,an interface engineering strategy based on a series of fluorophenethylamine organic spacer molecules has been developed.High quality two-dimensional perovskite was grown in situ on the surface of the three-dimensional perovskite active layer,achieving controllable construction of mixed-dimensional perovskite heterostructures.The transport dynamics of photo-generated carriers in heterostructure have been investigated through time-resolved photoluminescence techniques,and the passivation effect of two-dimensional perovskite on interfacial defects has been elucidated,reducing the charge capture cross-section.The change of the energy band structure of the perovskite heterojunction was analyzed by depth profiling technology,confirming that the wide-bandgap two-dimensional perovskite structure increases the energy barrier for the minority carrier transport at the interface,thereby inhibiting non-radiative recombination at the interface.Finally,the efficiency of the optimized devices based on the top interface design reached 24.74%,and it can still maintain an initial efficiency of 80%after 300 hours of continuous illumination at the maximum power point.The above systematic research results on crystal quality control and device interface design of perovskite materials provide a technical prototype for achieving efficient energy conversion and stable service of photovoltaic cells,and promote the further development and application of metal halide perovskite materials in the field of clean energy. |
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