TiO_2 nanoparticle-based electron transport layer with improved wettability for efficient planar-heterojunction perovskite solar cell

The electron transport layer （ETL） plays an important role in planar heterojunction perovskite solar cell （PSCs）, by affecting the light-harvesting, electron injection and transportation processes, and especially the crystal- lization of perovskite absorber. In this work, we utilized a commercial TKD-TiO2 nanoparticle with a small diameter of 6 nm for the first time to prepare a compact ETL by spin coating. The packing of small-size particles endowed TKD-TiO2 ETL an appropriate surface-wettability, which is beneficial to the crystallization of perovskite deposited via solution-processed method. The uniform and high-transmittance TKD-TiO2 films were successfully incorporated into PSCs as ETLs. Further careful optimization of ETL thickness gave birth to a highest power conversion efficiency of 11.0%, which was much higher than that of PSC using an ETL with the same thickness made by spray pyrolysis. This TKD-TiO2 provided a universal solar material suitable for the further large-scale production of PSCs. The excellent morphology and the convenient preparation method of TKD-TiO2 film gave it an extensive application in photovoltaic devices.

Achieving Intrinsic Dual-Band Excitonic Luminescence from a Single Three-Dimensional Perovskite Nanoparticle Through Ni^(2+)-Mediated Halide Anion Exchange

Rapid halide anion exchange easily occurring in metal-halide perovskite nanoparticles(NPs)makes it nearly impossible to create a single three-dimensional(3D)CsPbX_(3)(X=Cl,Br,I)NP that simultaneously comprises two separate perovskite components.To circumvent this problem,we first propose a Ni^(2+)-mediated halide anion-exchange strategy in zero-dimensional(0D)Ni^(2+)-doped Cs_(4)PbBr_(6)(Cs_(4)PbBr_(6):Ni)perovskites to achieve ultra-stable 3D CsPbX_(3)NPs with two coexisting different perovskite individuals of CsPbCl_(3)and/or CsPbBr_(3).By combining the experimental results with first-principles calculations,we confirm that the completely isolated[PbBr_(6)]4−octahedra in 0D Cs_(4)PbBr_(6):Ni NPs can restrict rapid halide anion exchange and the anion diffusion preferentially proceeds in the proximity of substitutional NiPb centers,namely[NiBr_(6)]4−octahedra in a meta-stable state,rather than in the 0D Cs_(4)PbBr_(6)and residual 3D CsPbBr_(3)regions,thereby delivering intrinsic dual-band excitonic luminescence from a single 3D CsPbX_(3)NP with a more stable and efficient CsPbCl_(3)component as compared to its counterparts synthesized using conventional methods.These new insights regarding the precise control of halide anion exchange enable the preparation of a new type of high-efficiency perovskite materials with suppressed anion interdiffusion for prospective optoelectronic devices.

Toward high performance microwave absorber by implanting La_(0.8)CoO_(3)nanoparticles on rGO

The advent of“intelligent era”brings our life more convenience,but the electromagnetic radiation sur-rounding us not only greatly threatens human health,also makes information leakage and hidden trouble to national defense security.Hence,it is very urgent to develop novel electromagnetic wave absorption materials with lightweight,strong absorption,tunable absorption frequency and broad band absorption.Herein,a novel electromagnetic wave absorber is obtained by constructing La_(0.8)CoO_(3)-rGO nanocompos-ite,where La_(0.8)CoO_(3)nanoparticles are anchored on graphene nanosheets by the electrostatic interaction between GO and La_(0.8)CoO_(3).The effect of hybridization ratio of La_(0.8)CoO_(3)and rGO on microwave ab-sorption properties is carefully studied.The optimal reflection loss of La_(0.8)CoO_(3)-rGO nanocomposite can reach-62.34 dB with the maximum effective bandwidth of 6.08 GHz,presenting 48.78%and 245.45%increment compared to bare La_(0.8)CoO_(3)nanoparticles,respectively.The effective absorption bandwidth covers a broad electromagnetic wave absorption band from Ku band to the C band by tailoring thickness of the absorbers from 2.4 mm to 4.4 mm.The fascinating electromagnetic wave absorption performance is attributed to the synergy effect of La_(0.8)CoO_(3)and rGO,which integrates magnetic and dielectric loss caused by resonance,conductance,relaxation,and scattering loss.This result confirms that La_(0.8)CoO_(3)-rGO nanocomposite is potential candidates toward high-efficiency microwave absorbers and provides a valuable pathway for designing high-performance microwave attenuation materials in the future.

Characterization of B site codoped LaFeO_3 nanoparticles prepared via co-precipitation route

LaFe（1-x-y）CoxPdyO3 [（x, y） =（0, 0）,（0.40, 0）,（0.38, 0.05）] nanoparticles were synthesized via a co-precipitation route using ammonium hydroxide, sodium hydroxide and ammonium carbonate as the precipitant and calcination at different temperatures to study the compositional driven structural changes in lanthanum ferrites.Analysis of X-ray diffraction（XRD） patterns confirms the formation of single-phase perovskite structure and existence of orthorhombic Pnma symmetry for calcined powders. Field emission scanning electron microscope（FESEM） observations show that Pd-doped powders yield finer particles along with narrower particle size distribution compared with LaFeO3 and LaFe（0.6）Co（0.4）O3. Moreover,using ammonia as the precipitant leads to a smaller mean particle size of powders compared to NaOH, as well as significant difference in morphology of the particles.Raman analysis reveals that both Co and Pd atoms substitute Fe site in perovskite structure with shifting of phonon modes. Comparing Raman spectra demonstrates the presence of more oxygen vacancies in Pd-doped perovskites. It can be concluded from the results that Pd is successfully incorporated into the perovskite structure by co-precipitation method.