Carrier Regulating Mechanism And Perovskite Photoelectric Characteristics In Multi-dimensional Micro-Nano Frameworks

The organic-inorganic lead halide perovskite solar cells?PSCs?has shown tremendous advances.With the advantages of high efficiency,low cost,simple structure and facile solution-based preparation,PSCs have become one of the most competitive and promising next-generation photovoltaic devices in the future.The carrier transport layer?CTL?includes the electron transport layer?ETL?and the hole transport layer?HTL?,which are essential for PSCs.In conventional forward PSCs,HTL can assist in hole extraction and prevent water and oxygen from damaging the perovskite layer.ETL can effectively transport electrons,and its good light transmittance is favorable for the absorption of light by perovskite,and the hydrophilic surface can make the perovskite precursor sufficiently spread better in preparation.Therefore,the effective CTL in PSCs can improve the power conversion efficiency?PCE?.Spiro-OMeTAD is a common hole transport material?HTM?,but it requires multiple oxidants and has the poor hydrophobicity.In this thesis,a facile two-dimensional?2D?Pb-based metal-organic framework?Pb-MOF?in hexagon sheet structure is developed.Based on experimental and model analysis,an oriented haloing multi-dimension growth effect of framework?SP-MOF?is further demonstrated when it is composited with organic Spiro-OMeTAD layer.With the multi-dimensional micro-nano framework,the composited layer shows the smoother surface,higher hydrophobicity and upshifted energy levels and electrical interfaces,in comparison to the Spiro-OMeTAD HTL layer.When the SP-MOF multi-dimensional micro-nano framework is used as HTL in PSCs,the cell reveals the higher power conversion efficiency and moisture-resistance feather.The average efficiency of cell with the composite layer is 13.17%,which is 25%larger than that with the oxidized Spiro-OMeTAD layer,and the cell can remain 54%efficiency of initial value even after 9days in an environment of 30%relative humidity,in contrast,the efficiency of cell with the oxidized Spiro-OMeTAD layer decays to 28%of initial value just after 7 days.Therefore,this composite can be used as a potential HTL for effective planar PSCs in forward structure.TiO₂ and SnO₂ are common electron transport materials?ETM?,but the transmittance and electronic mobility of TiO₂ are not ideal.In addtion,the low hydrophilicity of SnO₂ is unfavourable to the spread of the perovskite precursor solution.Thence,a simple multi-dimensional conductive heterojunction?MDCN?,composited by TiO₂,SnO₂ and Ti₃C₂T_X MXene,is facilely designed.Based on an oxygen vacancy scramble effect,the zero-dimensional?0D?anatase TiO₂ quantum dots?QDs?,surrounding on 2D conductive Ti₃C₂T_X sheets,are in situ rooted on 3D SnO₂ nanoparticles,constructing micro-nano TiO₂/SnO₂ heterojunctions.The MDCN forms the multi-dimention micro-nano framework.The fabrication is implemented in a controlled low-temperature anneal method in air and then in N₂ atmospheres.With the optimal MXene content,the optical property,the crystallinity of perovskite layer,and internal interfaces are all facilitated,contributing more amount of carrier with effective and rapid transferring in device.The champion PCE of resultant PSCs achieves19.14%,yet that of SnO₂ counterpart is just 16.83%.In addition,it can also maintain almost85%of its initial performance for more than 45 days in 30-40%humidity air,comparatively,the counterpart declines to just below 75%of its initial performance.Furthermore,the MDCN ETL exhibits almost negligible hysteresis characteristics,good repeatability and reliability,and provides new ideas for subsequent research and commercialization of PSCs.