Effects of precursor solution concentration on the properties and morphology of YBCO films deposited by TFA-MOD method

Epitaxial YBCO films were deposited on （100） LaAlO3 single-crystal substrates by metalorganic deposition of metal trifluoroacetate precursors with different concentrations. All the YBCO films have Tc around 91 K and Jc excess 2 MA/cm^2 at 77 K in zero field. XRD θ-2θscans show all the films have c-axis normal orientation. The FWHM （full width at half-maximum intensity） values of X-ray ω-scans of （005） reflection are 0.379°, 0.283°, and 0.543° for the YBCO thin films deposited with precursor solution concentrations of 1.52, 1.0, and 0.75 mol/L, respectively. With the concentration of the precursors decreasing, the thickness of the films decreases linearly. SEM micrographs show that porosities in the films become bigger with the precursor solution concentration decreasing. The big porosities in the film with the lowest concentration precursor deteriorate the superconducting property and make it have a wider superconducting transition and a lower Jc.

Stabilization of formamidinium lead iodide perovskite precursor solution for blade-coating efficient carbon electrode perovskite solar cells

Formamidinium lead triiodide(FAPbI_(3))is a research hotspot in perovskite photovoltaics due to its broad light absorption and proper thermal stability.However,quite a few researches focused on the stability of the FAPbI_(3) perovskite precursor solutions.Besides,the most efficient FAPbI_(3) layers are prepared by the spin-coating method,which is limited to the size of the device.Herein,the stability of FAPbI_(3) perovskite solution with methylammonium chloride(MACl)or cesium chloride(CsCl)additive is studied for preparing perovskite film through an upscalable blade-coating method.Each additive works well for achieving a high-quality FAPbI_(3) film,resulting in efficient carbon electrode perovskite solar cells(pero-SCs)in the ambient condition.However,the perovskite solution with MACl additive shows poor aging stability that noα-FAPbI_(3) phase is observed when the solution is aged over one week.While the perovskite solution with CsCl additive shows promising aging stability that it still forms high-quality pureα-FAPbI_(3) perovskite film even the solution is aged over one month.During the solution aging process,the MACl could be decomposed into methylamine which will form some unfavored intermediated phase inducingδ-phase FAPbI_(3).Whereas,replacing MACl with CsCl could effectively solve this issue.Our founding shows that there is a great need to develop a non-MACl FAPbI_(3) perovskite precursor solution for cost-effective preparation of pero-SCs.

Effects of precursor solution concentration on dielectric properties of (Pb,La)(Zr,Ti)O_3 antiferroelectric thick films by sol-gel processing

Pb0.97La0.02Zr0.95Ti0.05O3(PLZT)antiferroelectric thick films derived from different precursor solution concentrations are prepared on platinized silicon substrates by sol-gel processing.The films present polycrystalline perovskite structure with a(100)preferred orientation by X-ray diffraction(XRD)analysis.The antiferroelectricity of the films is confirmed by the double hysteresis behaviors of polarization and double-bufferfly response of dielectric constant under the applied electrical field.Antiferroelectric properties and dielectric constant are improved while the polarization characteristic values are reduced with the increase of precursor solution concentration.The films at higher precursor solution concentration exhibit excellent dielectric properties.

Strategies from small-area to scalable fabrication for perovskite solar cells

Recently,perovskite solar cells(PSCs) have flourished,and their power conversion efficiency(PCE) has increased from the initial 3.8% to 25.2% in 2019,which is an unprecedented advance.However,usually high-efficiency and stable PSCs are small-area devices prepared by spin coating.This method is not suitable for the preparation of large-area devices in commercialization.Therefore,there is an urgent need to develop new materials and methods for the scalable fabrication of PSCs.In this review,we first describe the common small-area PSCs preparation methods,understand the nucleation and crystal growth kinetics of perovskite,and analyze the reasons that hinder the development of small-area devices to large-area devices.Next,in order to meet the challenges of PSC’s scalable fabrication,we summarize and analyze four strategies:scaling up precursor solutions,scalable deposition methods for large-area films,scaling up charge-transport layers and back electrodes,developing solar modules.Finally,challenges and prospects are proposed to help researchers prepare high-efficiency large-area PSCs.

Instability of solution-processed perovskite films:origin and mitigation strategies

Perovskite solar cells(PSCs)are promising next-generation photovoltaics due to their unique optoelectronic properties and rapid rise in power conversion efficiency.However,the instability of perovskite materials and devices is a serious obstacle hindering technology commercialization.The quality of perovskite films,which is an important prerequisite for long-term stable PSCs,is determined by the quality of the precursor solution and the post-deposition treatment performed after perovskite formation.Herein,we review the origin of instability of solution-processed PSCs from the perspectives of the precursor solutions and the perovskite films.In addition,we summarize the recent strategies for improving the stability of the perovskite films.Finally,we pinpoint possible approaches to further advance their long-term stability.

Control of the hydrophobicity of rare earth oxide coatings deposited by solution precursor plasma spray by hydrocarbon adsorption

The basis of the hydrophobicity of lanthanide rare earth oxides(REOs)has been the subject of considerable debate.To explore this question,the wetting behaviors and surface compositions of hierarchicallystructured Yb_(2)o_(3)(one of the REOs)coatings and non-REO Al_(2)o_(3)coatings deposited via solution precursor plasma spray process were investigated in this work.The Yb_(2)o_(3)coatings were subjected to a number of post-deposition treatments including vacuum(1-15 Pa)treatment,Ar-plasma treatment,heat treatment(400℃),long-time air exposure and ultra-high vacuum(1×10^(-7)Pa)treatment.Subsequent characterization showed that different post-deposition treatments resulted in different wetting behavior for the Yb_(2)o_(3)coatings which correlated with the content of hydrocarbon on the surface.Yb_(2)o_(3)coatings exhibited reversible transitions between superhydrophobicity after vacuum treatment and superhydrophilicity after Ar-plasma or heat treatment,linked to hydrocarbon adsorption onto and desorption from the surface.Yb_(2)o_(3)coatings after long-time air exposure and ultra-high vacuum treatment both remained hydrophilic and showed a smaller hydrocarbon content than coatings after vacuum treatment.Al_(2)o_(3)coatings with hierarchical surface structures similar to the Yb_(2)o_(3)coatings showed an increase in WCA to only-170 after the same vacuum treatment,indicating the REO has a much higher affinity for hydrocarbon adsorption than Al_(2)o_(3),and that the content of hydrocarbon adsorbed on the surface of the REO determined the wetting behavior.

Significant effect of ordered micro-domain on cell boundary phase distribution and demagnetization curve squareness of Sm_(2)Co_(17)-type magnet

Cu-rich cell boundary phase is difficult to precipitate evenly,resulting in a generally poor demagnetization curve squareness for Fe-rich Sm_(2)Co_(17)-type magnet,which is a key factor limiting the further improvement of magnetic energy product.In this study,we report that nanoscale strip-like ordered micro-domains distributed in1:7H disordered matrix phase of the solid solution precursor is a new factor significantly affecting the precipitation and distribution of the cell boundary phase.Long strip-like and continuous micro-twin structure with twin boundaries neatly perpendicular to the C-axis is observed after sintering treatment.After solution treatment,sequential and long strip-like micro-twins gradually transform into disordered state along the basal plane,forming narrow disordered 1:7H(TbCu_(7)-type structure)phase between the separated strip-like ordered micro-domains.This disordering transformation takes place via broken down of the long strip-like ordered micro-domains,which is accomplished by narrowing along the width direction followed by reduction of the length.Furthermore,a new model revealing the effect of the ordered micro-domains on the formation of the cell boundary phase is proposed.Antiphase boundaries enriched in Cu have already existed in the precursor with long strip-like ordered micro-domains.Therefore,the Cu-rich cell boundary phase acting as strong pinning centers cannot be precipitated homogeneously and distributed continuously after aging,resulting in a poor demagnetization curve squareness of Sm_(2)Co_(17)-type magnet.Our results indicate that significant broken down of the nanoscale ordered micro-domains in solution precursor is the key factor improving the distribution of cell boundary phase in Sm_(2)Co_(17)-type magnets.

Selective synthesis and growth mechanism of CeVO_4 nanoparticals via hydrothermal method

Selective-controlled structure and shape of CeVO4 nanocrystals were successfully synthesized via a hydrothermal method from Na3VO4·12H2O and Ce（NO3）3·6H2O.The resulting products were characterized by X-ray powder diffraction （XRD）,field emission scanning electron microscopy （FESEM） and energy dispersive spectroscopy （EDS）.The influence of hydrothermal temperature,precursor solution concentration on the crystal and morphology of products were further studied.The results showed that the as-synthesized products exhibited pure single-crystal CeVO4 nanoparticles with tetragonal structure.The hydrothermal temperature and precursor solution concentration had important effects on the formation of CeVO4 nanoparticles.Furthermore,the growth mechanism of CeVO4 nanoparticles was explained with Ostwald ripening mechanism.

Active-layer evolution and （CH3NH3）3Bi2l9-based solar substrate efficiency improvement of cell on TiO2-deposited ITO

We systematically investigated the development of film morphology and crystallinity of methyl-ammonium bismuth （Ⅲ） iodide （MA3Bi2I9） through one- step spin-coating on TiO2-deposited indium tin oxide （ITO）/glass. The precursor solution concentration and substrate structure have been demonstrated to be critically important in the active-layer evolution of the MA3Bi2I9-based solar cell. This work successfully improved the cell efficiency to 0.42% （average： 0.38%） with the mesoscopic architecture of ITO/compact-TiOdmesoscopic-TiO2 （meso-TiO2）/ MA3Bi2I9/2,2＇,7,7＇-tetrakis（N,N-di-4-methoxyphenylamino）-9,9＇spiro-bifluorene （spiro-MeOTAD）/MoO3/Ag under a precursor concentration of 0.45 M, which provided the probability of further improving the efficiency of the BiB＋-based lead-free organic-inorganic hybrid solar cells.