@article {48341, title = {Lead-free solid state mechanochemical synthesis of Cs2NaBi1-XFeXCl6 double perovskite: reduces band gap and enhances optical properties}, journal = {Inorganic Chemistry}, volume = {62}, year = {2023}, month = {MAR}, pages = {4861-4871}, type = {Article}, abstract = {

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.

}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.2c04149}, author = {Udavant, Rohini and Thawarkar, Sachin and Rondiya, Sachin and Shelke, Ankita and Aher, Rahul and Ajithkumar, Thalasseril G. and Cross, Russell W. and Dzade, Nelson Y. and Jadkar, Sandesh} } @article {49463, title = {Lead-free Cs2AgBiCl6 double perovskite: experimental and theoretical insights into the self-trapping for optoelectronic applications}, journal = {ACS Physical Chemistry Au}, volume = {4}, year = {2024}, month = {JUL}, pages = {476{\textendash}489}, type = {Article}, abstract = {

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{\textendash}computational approach is employed to investigate the optoelectronic properties of pure and doped Cs2AgBiCl6\ (Fe{\textendash}Cs2AgBiCl6) perovskites. Successful incorporation of Fe3+\ ions is confirmed by X-ray diffraction and Raman spectroscopy. Moreover, the Fe{\textendash}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{\textendash}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.

}, doi = {https://doi.org/10.1021/acsphyschemau.4c00008}, author = {Rahane, Swati N. and Rahane, Ganesh K. and Mandal, Animesh and Jadhav, Yogesh and Godha, Akshat and Rokade, Avinash and Shah, Shruti and Hase, Yogesh and Waghmare, Ashish and Saykar, Nilesh G. and Roy, Anurag and Salgaonkar, Kranti N. and Dubal, Deepak and Makineni, Surendra K. and Dzade, Nelson Y. and Jadkar, Sandesh R. and Rondiya, Sachin R.} }