Application Research Of Co-MOFs Derived Carbon Composite Materials In Perovskite Solar Cells

The development and application of clean energy,especially solar energy,is an effective way to solve energy crisis and environmental problems.Perovskite solar cells（PSCs）are garnered great attention in the scientific community due to their high power conversion efficiency（PCE）.However,high cost and low stability are hindered their commercialization.Replacing organic hole transport materials（HTM）and Au electrode with carbon electrode is a promising way to address the stability issues of PSCs because carbon materials are stable,inert to ion migration,and inherently water-resistant.However,carbon-based perovskite solar cells（C-PSCs）show the poor performance that charge carrier extraction by the carbon electrode alone is not as efficient as in the case of conventional hole transport materials（HTMs）based PSCs.In response to these problems,this paper proposes some improvement measures to fix the shortcomings of carbon electrodes.The nitrogen-doped porous carbon/metal composite material with excellent conductivity is used as a hole transport modifier and incorporated into CE to greatly improve the PSK/CE interface quality and charge transfer performance.The strategy of inserting a suitable inorganic hole transport layer and combining it with a novel controllable ultraviolet/ozone（UVO）treatment to improve the PSK/CE interface achieves higher efficiency PCE for carbon-based perovskite solar cells（C-PSCs）.（1）Research on the application of MOFs-derived conductive porous carbon materials to the counter electrode of perovskite solar cells:In this chapter,the nitrogen-doped metal/carbon（Metal@NC）nanomaterials are obtained from the pyrolysis of metal organic frameworks（MOFs）is applied to the CE,which efficiently improves interface performance of perovskite/CE,suppresses charge recombination and promotes hole extraction,consequently enhancing the photovoltaic performance.We here chose Zeolite imidazolium Framework-67（ZIF-67）as a sacrifice template for the preparation of Metal@NC nanomaterials owing to its high surface area and porosity,abundant nitrogen and cobalt atoms in the skeleton.After etching by HCl,Metal@NC nanomaterials are formed a coexisting structure of micro-mesopores.At the same time,the carbon shell can form an interfacial barrier,which not only protects part of the carbon-coated nano-cobalt from being dissolved,but also prevents the"metal-halides perovskites"reaction.Our experimental results demonstrate that nitrogen and cobalt are effectively doped into the carbon matrix which enhances the electrical conductivity,thereby contributing to efficient charge extraction.In particular,the maximum PCE of 10.72%is achieved in the ambient atmosphere,achieving 43%increasing over the pure CC-based device（7.49%）.The significant increase in the final PCE and its mechanism analysis provides an archetypical useful template to explore the potential of upgrading C-PSCs in the future.（2）Research on the application of MOFs-derived hole transport materials to perovskite solar cells:Nevertheless,the hole-selectivity of carbon is inefficient and the energy offset between the valence band（～-5.4 e V）of MAPb I₃ and work function（～-5.0e V）of carbon is as high as 0.4 e V,which affects the efficiency of hole extraction and the alignment of energy level,leading to seriously poor contact at the MAPb I₃/Carbon electrode（CE）interface as well as a marked loss of charge transform and therefore deteriorates the performance of the C-PSCs.In this work,Co₃O₄@NC nanoparticles with two distinct morphologies are prepared using different ZIF-67 precursor and calcination temperature.We design and optimize the structure of C-PSCs through interface engineering by using MOFs derived ultrafine Co₃O₄@NC nanocrystals as a buffer layer.These strategies play remarkable multifunctional roles:（i）adjust the energy level in the planar PSC with a structure of FTO/Sn O₂/MAPb I₃/Co₃O₄@NC/CE;（ii）optimize the PSK/CE interface;and（iii）induce the defect passivation and suppresse the charge recombination.These advantages result in C-PSCs without encapsulation achieves a maximum PCE up to 14.63%,and also show long-term stability in air.（3）UV-ozone treatment of MOFs-derived hole transport materials are applied to perovskite solar cells:In this chapter,a simple processing method on the Co₃O₄@NC nanoparticles manipulate by controllable ultraviolet/ozone（UVO）treatment is employed,to further improve the interfacial performance of MAPb I₃/Co₃O₄@NC and reduce the hysteresis.These as-prepared Co₃O₄@NC-600 samples are treated by UVO treatment at different time（0 min,1 min,5 min,10 min）respectively.The measurement shows drastic change of surface tension and electrical conductivity with the UVO treatment.Moreover,high energy photons could also influence the oxidization state and crystalline situation in the oxides.Therefore,the chemical and microstructural properties of the objects are further investigated.These changes affect the interface contact and interface performance with adjacent materials,which benefit for good coverage of perovskite film,achieving more effective hole extraction and lower recombination.Through optimization,the unpackaged optimal C-PSCs achieve a maximum PCE of 14.63%.PSCs also show long-term stability in the air.