| Organic-inorganic hybrid perovskite materials have some advantages such as high light absorption coefficient,easy-to-adjust energy band structure,strong electron/hole transmission capacity and high defect tolerance.In the past decade,the power conversion efficiency(PCE)of perovskite solar cells(PSCs)has rapidly increased from3.8%in 2009 to 25.7%at present.PSCs have advantages of simple fabrication and low cost compared to silicon solar cells.However,PSCs are sensitive to external factors such as temperature,humidity,ultraviolet,and oxygen,which can greatly affect the stability of PSCs and hinder their commercial application.According to problems of PSC stability,an encapsulation structure jointly using ethylene-vinyl acetate copolymer(EVA)and paraffin has been developed and applied to PSCs based on Ni O_X as the hole transport layer,which greatly improves the stability of PSCs.In the meanwhile,using the interface modification technology,the antioxidant MD-697 doped PVK modified layer was introduced to the interface of the perovskite/electron transport layer(PCBM),which significantly improved PCE and stability of PSCs.The stability of MD-697:PVK modified PSCs can further be improved using the encapsulation structure with paraffin/EVA/paraffin.The main results are as follows:1.The composite encapsulation technology with paraffin and EVA hot melt adhesive has been developed and the decay trend and related mechanism of PSCs encapsulated with paraffin/EVA/paraffin and pure EVA were compared and investigated,respectively.PSCs encapsulated with paraffin/EVA/paraffin still remained 95%of the original PCE after aging for 1000 h under 75%relative humidity(RH)and its PCEs kept 98%of the initial value after soaking in water for 5 h.The paraffin/EVA/paraffin structure using the high melting point of 68℃paraffin show better encapsulating performance compared to paraffin with the low melting points(55℃and 60℃).Because paraffin has good fluidity and wettability,which can be immersed into the defects,cavities,and edge areas of metal electrodes to inhibit the deterioration of metal electrodes of these areas.Therefore,adopting paraffin/EVA/paraffin encapsulating structure can not only use the advantage of the continuous and solid characteristics of EVA film,but also the excellent hydrophobicity and wettability of paraffin,which can form a continuous,dense and high hydrophobic composite encapsulating layer,significantly improving the stability of PSCs.This paraffin/EVA/paraffin encapsulation with solvent-free can operate at low temperatures under the atmospheric environment,reducing low cost of PSCs,which give a new idea for encapsulating PSCs.2.The strategy of antioxidant MD-697 doped poly(9-vinyl carbazole)(PVK)modified the interface of the perovskite/electron transport layer,which can form a dense and continuous quasi-two-dimension(2D)modified layer on the surface of 3D perovskite film.The quasi-2D modified layer can prevent the direct exposure of grain boundaries,significantly improve the crystallinity and stability of the perovskite layer.In the meantime,modified layer can passivate the defects at grain boundaries and interfaces,improve the interface contact performance,promote the transport and extraction of carriers.The MD-697:PVK modified PSCs increased from 17.1%PCE of the reference PSCs to 20.7%,and significantly inhibited the hysteresis phenomena.The unencapsulated MD-697:PVK modified PSCs still maintained 60%of the original PCE value after 12 h UV irradiation,while PVK modified PSCs failed after 8 h UV irradiation.The MD-697:PVK-modified PSCs maintained 92%of the original PCE,while reference and PVK-modified PSCs remained respectively 84%and 87%of the original PCE aged 65°C and 85%RH for 1200 hours under paraffin/EVA/paraffin encapsulating conditions.Therefore,the strategy jointly using antioxidant MD-697 and PVK to modify the perovskite/PCBM interface can significantly improve PCE and stability(light,moisture and heat)of PSCs,which provides a new idea to obtain efficient and stable PSCs. |
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