| Global energy demand has been continually increasing with the rapid development of industries and population growth in recent decades.The development of renewable and green energy alternatives has caused great concern and devoted numerous investigations in both academy and engineering in the world.Solar cells which convert sunlight directly into electricity,possessing cost-effective,reliable and safe as well as flexible attributes,was regarded as the most promising renewable energy technology.The emerging thin-film solar cells based on the organometal halide with the perovskite structure serving as high-efficiency light sensitizer,namely perovskite solar cells(PSCs),becomes one of the most promising candidates for cost-effective third-generation solar cells because of their amazing photovoltaic performance as well as low cost.Generally,the efficiency,cost and stability were regarded as the three most crucial factors for solar cells in commercial applications,and it remains huge challenge to further increase conversion efficiency and durability for PSCs.In this context,the researches of PSCs in the recent years mainly emphasize the preparation of high-quality perovskite film,high-performance electron and hole transfer layer and the optimization of the separation and transfer of photo-generated carriers.Among them,interface engineering as well as dopant strategy have received a considerable interest and become a hot-topic research in PSC field.In this thesis,we concentrate our research on the interface engineering as well as doped-perovskite technology,and mainly develop the graphene derivatives and polymer films for interface engineering application to further increase the efficiency of PSCs as well as their long-term stability against the humidity.The main research contents and progress are listed as follows:(1)An amino-rich graphene(NGs)prepared by the phenylenediamine(PPDA)surface modifier in combination with the chemical reduction method was developed as an interlayer at the perovskite/hole transfer layer interface for the first time.It was demonstrated that the resultant NGs via the facile solution process exhibited amino-rich groups on the surface as well as high reduction extent.Also,the uniform NGs sheets were successfully deposited on the perovskite surface in a relatively large domain,which could passivate the perovskite film effectively.After the surface engineering with the NGs,the PL peak exhibited a slight blue-shift,corresponding to the reduced surface traps of the perovskite film.In addition,compared to the control devices,the PSCs based on the NGs interlayer obtained higher built-in potential,recombination resistance as well as electron lifetime,suggesting the efficient blocking of the charge recombination at the interface.Consequently,a maximum efficiency of 14.60%was reached based on such dual-functional role of NGs interlayer at the perovskite/hole transfer layer interface,representing a remarkable improvement of ca.36%over the control device(10.70%),which was mainly due to the increase of JSC andFF.(2)A low-cost and insulating polystyrene nanofilm was introduced at the interface of perovskite/hole transfer layer for the first time.It was demonstrated that a continuous PS film was fully covered on the perovskite substrate.The covered PS nanofilm prevented the direct contact of perovskite sensitizor from the hole transfer layer,which allow the tunneling of the photo-generated holes while blocking the transfer of electrons.Thus,this PS film contact behaved as a spatial separation layer at the interface effectively.Compared to the control dcvices,the PSCs with the modification of the PS interlayer were of higher recombination resistance and electron lifetime,enabling to the efficiently reduce the charge recombination at the interface.In addition,the hydrophobic PS nanofilm at the interface of perovskite/hole transfer layer can really act as the water-resistant layer for perovskite film,and a significantly increased water contact angle(98.11°)was achieved compared to that of the control device(86.41°).Consequently,based on such dual-functional role of PS interlayer at the perovskite/hole transfer layer interface,a maximum efficiency of 17.80%was gained for the PS-modified PSCs,which showed a remarkable efficiency improvement than that of the control one(15.90%);Meanwhile,the PSC devices with PS modification retained over 70%of the original efficiency after 250 h exposure in the dark air with a relative humidity of 45%without any encapsulation layer,while the control cell only maintained 23%.(3)An positively charged nitrogen-rich graphene(N-GEs)prepared by the poly(diallyldimethylammonium chloride)(PDDA)surface modifier in combination with the chemical reduction method was developed as an dopant for the perovskite sensitizer for PSCs application for the first time.It was demonstrated that the resultant N-GEs via the facile solution process exhibited nitrogen-rich groups on the surface,high reduction as well as high exfoliation extent.Meanwhile,the N-GEs displayed an excellent dispersibility in the organic solvent such as DMF.Also,the doped N-GEscan not only maintain the superior crystal form,but also improve the crystallization process of perovskite material.So,the resultant perovskite film based on the N-GEs dopant exhibited a significantly enhanced crystallinity as well as grain size.In addition,compared to the undoped perovskite film,the introduction of N-GEs significantly improved the optical absorption behavior of perovskite sensitizer,and also passivated the perovskite surface,corresponding to the reduced surface defect.Consequently,the resultant PSC devices with the modification of N-GEs dopant exhibited an enhanced photovoltaic performance,and a maximum efficiency of 17.53%was reached for the N-GEs doped PSCs with a concentration of 0.25 mg/mL,indicating a remarkable improvement of efficiency than that of the control one(15.88%). |
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