Lattice Interface Regulating Bismuthene-based Heterojunction And Performance Research Of Perovskite Solar Cells

Since the twenty-first century（2009）,organic-inorganic hybrid perovskite materials have been tried to be applied to the photovoltaic field for the first time.Because of its excellent performance and low cost,it has attracted the attention of more and more researchers.With the development in the industrial domain and the optimization of the process,perovskite solar cells（PSCs）have become the excellent competitive advantages and become the new star of photovoltaic devices in the future.In order to realize the photovoltaic function,the device has a beneficial functional layer,which includes two charge transport layers（for electrons and holes respectively）.The perovskite layer is between the charge transport layers which the energy levels must match each other.For electron transporting layers（ETL）,the high-performance ETL has the following two conditions:ETL conduction band and valence band edge are lower than perovskite layer conduction band and valence band edge.TiO₂ and SnO₂ are the most widely studied electron transport layer materials（ETM）,but they have many disadvantages.For example,TiO₂ has lower conductivity and lower electron mobility;SnO₂ has poor hydrophilicity which is not conducive to the spread of the perovskite layer solution.In order to pursue better performance,the research on ETL by scientific researchers has never stopped.Today,the discovery and application of 2D materials had given us enlightenment,and they will soon be applied to photovoltaic devices such as solar cells and supercapacitors.Each material has its own excellent characteristics point out the direction for our next research.In explore the attractive structural and semiconductive properties of two-dimensional bismuthene,exquisite heterojunctions with less interfacial mismatch between bismuthene and SnO₂ nanoparticle are coincidentally architected by a low-temperature procedure,based on an unique self-adaptive attribute of two-dimensional structure of bismuthene,in combination with a lattice-matching attribute of adjacent lattice-spacing between bismuthene and SnO₂.Applied in perovskite solar cells as electron transport layer,the bismuthene-SnO₂ composite layer turns smoother and transparenter,and endows higher crystallinity for upper perovskite layer.Relying on highly-conductive bismuthene along with semiconductive bismuthene-SnO₂ heterojunctions,the energy band of integral composite layer is upshifted and the interfacial resistance between composite layer and perovskite layer is reduced,effectively accelerating the electron-extracting without declining the hole-blocking,in comparison with pure SnO₂ layer.The higher statistical average power conversion efficiency of 18.75%is achieved,compared to the counterpart of 17.35%,and it also maintained high stability almost 80%of its initial efficiency even in～5%relative humidity environment more than 800 hours,contrastly the counterpart just maintains 50%efficiency retention.At the same time,a simple bismuthene-MXene-SnO₂ multi-doped ETL（BMSE）,composited by bismuthene,SnO₂ and MXene is facilely designed.Based on the oxygen vacancy contention effect with low-temperature annealing in the air,multi-doped BMSE was constructed.By combining the previous work and optimizing the MXene content,the interface is optimized and the effective and rapid transfer of electrons in the device is increased.The highest PCE of PSCs reached 19.78%,while the SnO₂ sample was only 18.62%.In addition,PSCs based on BMSE can be placed in the air with a humidity of 30%to 40%for more than 240 hours and still maintain75%of their initial performance.In contrast,the PCE of the SnO₂ sample drops below its initial performance 60% of it.