02809nas a2200229 4500008004100000245015400041210006900195260000900264300001600273490000700289520194400296100002402240700002202264700002702286700002202313700002302335700002102358700002402379700002502403700002202428856012902450 2020 eng d00aUncovering the origin of enhanced field emission properties of rGO-MnO(2)heterostructures: a synergistic experimental and computational investigation0 aUncovering the origin of enhanced field emission properties of r cJUL  a25988-259980 v103 a

The unique structural merits of heterostructured nanomaterials including the electronic interaction, interfacial bonding and synergistic effects make them attractive for fabricating highly efficient optoelectronic devices. Herein, we report the synthesis of MnO(2)nanorods and a rGO/MnO(2)nano-heterostructure using low-cost hydrothermal and modified Hummers' methods, respectively. Detailed characterization and confirmation of the structural and morphological properties are doneviaX-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). Compared to the isolated MnO(2)nanorods, the rGO/MnO(2)nano-heterostructure exhibits impressive field emission (FE) performance in terms of the low turn-on field of 1.4 V mu m(-1)for an emission current density of 10 mu A cm(-2)and a high current density of 600 mu A cm(-2)at a relatively very low applied electric field of 3.1 V mu m(-1). The isolated MnO(2)nanorods display a high turn-on field of 7.1 for an emission current density of 10 mu A cm(-2)and a low current density of 221 mu A cm(-2)at an applied field of 8.1 V mu m(-1). Besides the superior FE characteristics of the rGO/MnO(2)nano-heterostructure, the emission current remains quite stable over the continuous 2 h period of measurement. The improvement of the FE characteristics of the rGO/MnO(2)nano-heterostructure can be ascribed to the nanometric features and the lower work function (6.01 and 6.12 eV for the rGO with 8% and 16% oxygen content) compared to the isolated alpha-MnO2(100) surface (phi= 7.22 eV) as predicted from complementary first-principles electronic structure calculations based on density functional theory (DFT) methods. These results suggest that an appropriate coupling of rGO with MnO(2)nanorods would have a synergistic effect of lowering the electronic work function, resulting in a beneficial tuning of the FE characteristics.

1 aRondiya, Sachin, R.1 aKarbhal, Indrapal1 aJadhav, Chandradip, D.1 aNasane, Mamta, P.1 aDavies, Thomas, E.1 aShelke, Manjusha1 aJadkar, Sandesh, R.1 aChavan, Padmakar, G.1 aDzade, Nelson, Y. uhttps://library.ncl.res.in/content/uncovering-origin-enhanced-field-emission-properties-rgo-mno2heterostructures-synergistic02758nas a2200241 4500008004100000022001400041245014000055210006900195260000800264300001400272490000700286520189900293100002002192700002202212700002002234700001902254700001602273700003202289700002302321700002202344700002002366856013002386 2023 eng d a0020-166900aLead-free solid state mechanochemical synthesis of Cs2NaBi1-XFeXCl6 double perovskite: reduces band gap and enhances optical properties0 aLeadfree solid state mechanochemical synthesis of Cs2NaBi1XFeXCl cMAR a4861-48710 v623 a

Efficient and stable lead-free halide double perovskites (DPs) have attracted great attention for the future generation of electronic devices. Herein, we have developed a doping approach to incorporate Fe3+ ions into the Cs2NaBiCl6 crystal unit and reveal a crystallographic and optoelectronic study of the Cs2NaBi1-xFexCl6 double perovskite. We report a simple solid-state mechanochemical method that has a solvent-free, one-step, green chemistry approach for the synthesis of Cs2NaBi1-xFexCl6 phosphor. The analysis of powder X-ray diffraction (XRD) data determines the contraction of the lattice due to the incorporation of Fe3+ cations, and this effect is well supported by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and solid-state nuclear magnetic resonance spectroscopy (ss-NMR). The band gap is reduced with increasing Fe content owing to the strong overlap of the Fe-3d orbitals with Cl-3p orbitals and shift of the valence band maxima (VBM) toward higher energies, as confirmed by ultraviolet photoelectron spectroscopy (UPS) and density functional theory (DFT) analyses. Photoluminescence (PL) studies of Cs2NaBi1-xFexCl6 phosphors exhibit a large Stokes shift, broadband emission, and increased PL intensity more than ten times for 15% of Fe content phosphor with enhancement in the average decay lifetimes (up to 38 ns) compared to pristine Cs2NaBiCl6 DP. These results indicate that the transition of dark self-trapping of excitons (STEs) into bright STEs enhances yellow emission. XRD, UV, and thermo-gravimetric analysis (TGA) confirmed that the Cs2NaB1-xFexCl6 DPs have good structural and thermal stabilities. Our findings indicate that the doping of Fe3+ cations into the Cs2NaBiCl6 lattice is a constructive strategy to enhance significantly the optoelectronic properties of these phosphors.

1 aUdavant, Rohini1 aThawarkar, Sachin1 aRondiya, Sachin1 aShelke, Ankita1 aAher, Rahul1 aAjithkumar, Thalasseril, G.1 aCross, Russell, W.1 aDzade, Nelson, Y.1 aJadkar, Sandesh uhttps://library.ncl.res.in/content/lead-free-solid-state-mechanochemical-synthesis-cs2nabi1-xfexcl6-double-perovskite-reduces05784nas a2200325 4500008004100000245013700041210006900178260000800247300001400255490000600269520469500275100002204970700002304992700002005015700001905035700001805054700002005072700001705092700001705109700002105126700002305147700001605170700002705186700001805213700002705231700002205258700002405280700002405304856013005328 2024 eng d00aLead-free Cs2AgBiCl6 double perovskite: experimental and theoretical insights into the self-trapping for optoelectronic applications0 aLeadfree Cs2AgBiCl6 double perovskite experimental and theoretic cJUL a476–4890 v43 a

Lead-free double perovskites (DPs) will emerge as viable and environmentally safe substitutes for Pb-halide perovskites, demonstrating stability and nontoxicity if their optoelectronic property is greatly improved. Doping has been experimentally validated as a powerful tool for enhancing optoelectronic properties and concurrently reducing the defect state density in DP materials. Fundamental understanding of the optical properties of DPs, particularly the self-trapped exciton (STEs) dynamics, plays a critical role in a range of optoelectronic applications. Our study investigates how Fe doping influences the structural and optical properties of Cs2AgBiCl6 DPs by understanding their STEs dynamics, which is currently lacking in the literature. A combined experimental–computational approach is employed to investigate the optoelectronic properties of pure and doped Cs2AgBiCl6 (Fe–Cs2AgBiCl6) perovskites. Successful incorporation of Fe3+ ions is confirmed by X-ray diffraction and Raman spectroscopy. Moreover, the Fe–Cs2AgBiCl6 DPs exhibit strong absorption from below 400 nm up to 700 nm, indicating sub-band gap state transitions originating from surface defects. Photoluminescence (PL) analysis demonstrates a significant enhancement in the PL intensity, attributed to an increased radiative recombination rate and higher STE density. The radiative kinetics and average lifetime are investigated by the time-resolved PL (TRPL) method; in addition, temperature-dependent PL measurements provide valuable insights into activation energy and exciton–phonon coupling strength. Our findings will not only deepen our understanding of charge carrier dynamics associated with STEs but also pave the way for the design of some promising perovskite materials for use in optoelectronics and photocatalysis.

1 aRahane, Swati, N.1 aRahane, Ganesh, K.1 aMandal, Animesh1 aJadhav, Yogesh1 aGodha, Akshat1 aRokade, Avinash1 aShah, Shruti1 aHase, Yogesh1 aWaghmare, Ashish1 aSaykar, Nilesh, G.1 aRoy, Anurag1 aSalgaonkar, Kranti, N.1 aDubal, Deepak1 aMakineni, Surendra, K.1 aDzade, Nelson, Y.1 aJadkar, Sandesh, R.1 aRondiya, Sachin, R. uhttps://library.ncl.res.in/content/lead-free-cs2agbicl6-double-perovskite-experimental-and-theoretical-insights-self-trapping