Interface Engineering Of Novel Charge Transport Materials In Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells(PSCs)have achieved a breakthrough in power conversion efficiency(PCE)from 3.8%to 25.2%in recent years,and are known as the next-generation thin-film solar cells with broad development prospects.The performance of PSCs depends not only on the material of the devices,but also on the interface properties between the layers of materials.They play a significant role in the extraction,transportation,and recombination of charges.In this work,we designed the charge transport materials and optimized its interface with perovskite layers,explored the mechanism of interface engineering by novel transport materials for improving the photovoltaic performance of PSCs,and systematically recognized the impact of device components and interfaces on the efficiency and longterm stability of PSCs.1.Enhanced efficiency and stability of planar perovskite solar cells using a dual electron transport layer of gold nanoparticles embedded in anatase TiO2 filmsIncorporating plasmonic nanostructures is a promising strategy to enhance both the optical and electrical characteristics of photovoltaic devices via more efficient harvesting of incident light.Herein,we report a facile and low-temperature fabrication scheme for producing gold nanoparticles embedded in anatase TiO2 films,which can simultaneously improve the efficiency and stability of PSCs.The n-i-p PSCs based on rigid and flexible substrates with 0.2 wt.%Au-TiO2/TiO2 dual electron transport layers(ETLs)achieved PCE up to 20.31%and 15.36%,respectively,superior to that of devices with TiO2 as a single ETL.Moreover,0.2 wt.%Au-TiO2/TiO2 devices demonstrated significant stability in light soaking,which is attributed to improved light absorption,low charge recombination loss and enhanced carrier transport and extraction in the presence of the plasmonic Au-TiO2/TiO2 dual ETL.The present work improves the practicability of high-performance and flexible PSCs by engineering the photogenerated carrier dynamics at the interface.2.Conjugated polymer-graphene oxide composites as an ultra-thin passivation layer to improve PSCs device performanceIn this work,we present a new route to synthesize poly[(2-methoxy,5-octoxy)1,4phenylenevinylene](MOPPV)on few-layer graphene oxide(GO)by in-situ polymerization method at room temperature.The novel nanocomposite MOPPV-GO is employed as the ultra-thin passivation layer of PSCs.The structure of the PSCs is ITO/TiO2/(FAPbI3)x(MAPbCl3)1-x/MOPPV-GO/Spiro-OMeTAD/Ag.MOPPV-GO can fully combine the advantages of the two materials.After introduction of MOPPV-GO on the perovskite layer,a uniform thin film can be formed on the surface,so that dense contact of perovskite with the hole transport layer is formed.MOPPV uses GO as a substrate to form a denser conjugate network,which significantly improves electrical property.The result shows that MOPPV-GO can not only effectively passivate defects at the surface and grain boundaries of perovskite film,but also improve the crystallinity of the perovskite.Therefore,the charge extraction and transportation are enhanced dramatically.Compared with the control devices,the PCE of the PSCs with MOPPVGO has been greatly increased from 16.42%to 19.73%.This work could come up with a new idea for the synthesis and application of graphene-based materials in solar cells.3.Conjugated polymer as the passivating agent to improve the long-term stability of PSCsAlthough PSCs show excellent photovoltaic performance,the long-term stability of PSCs becomes a serious challenge due to the hygroscopicity of the perovskite materials.In this chapter,PffBT4T-C9C13 was introduced to the perovskite/hole transport layer interface for the first time.The result shows that this novel conjugated polymer can improve the photovoltaic performance of the device with a best PCE of 20.21%on a rigid substrate,far more than that of the control device(17.16%).The stability test shows that the passivation agent can effectively block the external water vapor from the perovskite film.Compared with the devices without PffBT4T-C9C13,the efficiency of the modified PSCs remained 81%of the original efficiency under continuous monitoring of～400 h at a humidity of～40-50%,showing excellent longterm stability.