Crystallization Regulation and Morphological Evolution for HTM-free Tin-Lead (1.28eV) Alloyed Perovskite Solar Cells

There have been huge achievements of all-perovskite tandem solar cells,which recently realized the highest power conversion efficiency of 24.8%.However,the complex device structure and complicated manufacture processes severely restrict the further development of all-perovskite tandem solar cells.In this work,we successfully fabricated high-efficiency hole transport material-free(HTM-free)Sn−Pb alloyed narrow bandgap perovskite solar cells(PSCs)by introducing guanidinium thiocyanate(GASCN)and hydroiodic acid(HI)into the perovskite precursor solution.GASCN and HI play a positive synergy effect during perovskite crystallization process resulting in larger grain size,fewer surface defects,and lower trap density to suppress the Sn^(2+)oxidation degradation.Furthermore,they could effectively adjust the energy level of perovskite materials,reduce the energy level difference between perovskite and ITO resulting in more efficiently transport of free hole charge carriers.As a result,with adding GASCN and HI,the achieved highest power conversion efficiency of HTM-free devices increased from 12.58%to 17.85%,which is one of the highest PCEs among all values reported to date for the HTM-free narrow-bandgap(1.2-1.4 eV)Sn−Pb binary PSCs.Moreover,the optimized device shows improved environmental stability.Our additive strategy manifests a remarkable step towards the facile,cost-efficient fabrication of HTM-free perovskite-based tandem solar cells with both high efficiency and simple fabrication process.

Ultralow-loss (1-x)CaWO_(4)-xNa_(2)WO_(4) (x=0.1,0.2) microwave dielectric ceramic for LTCC applications

In this work,the(1-x)CaWO_(4)-xNa_(2)WO_(4)(x=0.1,0.2,denoted as 0.9CW-0.1NW and 0.8CW-0.2NW,respectively)ultralow-loss microwave dielectric ceramics were prepared via solid-state reaction method.Using low melting-point Na_(2)WO_(4) as sintering aid to prepare CaW_(O4)eNa_(2)WO_(4) composite ceramics,the sintering temperature of CaWO_(4) was successfully reduced while maintaining excellent microwave performance.The optimal microwave dielectric properties have been achieved at 900C for 0.9CW-0.1NW ceramic:εr=9.0,Q×f=105660 GHz,tandδ=1.1×10^(-4)and tf=35.4 ppm/℃ at a frequency of 12.0 GHz.For the 0.8CW-0.2NW ceramic,the optimal microwave dielectric properties have been obtained at 740C,withεr=8.5,Q×f=97014 GHz,tandδ=1.2×10^(-4)and tf=37.4 ppm/℃ at a frequency of 11.8 GHz.In summary,both composite ceramics exhibit low sintering temperatures,excellent dielectric properties and chemical compatibility with the Ag electrode.The findings of this study provide an effective approach to prepare novel composite ceramics as promising candidates for LTCC applications.