Bandgap engineering and sublattice distortion driven bandgap bowing in Cs2Ag1-xNaxBiCl6 double perovskites

Bandgap engineering in lead-free Cs2Ag1-xNaxBiCl6 (x = 0 to 1) double perovskite alloys synthesized through solution-based approach is investigated. The bandgap is shown to vary from 2.64 eV to 3.01 eV as Ag+ at B′ site gets replaced with Na+ cation. Despite a linear change in the lattice parameter according to Vegard's law, bandgap (Eg) changes in a nonlinear fashion for x = 0 to 1 with much lower Eg values observed than predicted by Vegard's rule. Further, we show the bandgap bowing effect in Cs2Ag1-xNaxBiCl6. Raman spectroscopic studies reveal that the changes in the vibrational mode positions arise due to the systematic variations in local distortions of [BiCl6]3– and [AgCl6]5– octahedra. The bandgap change, Raman mode frequency shift, Raman peak width, and the ratio of intensities of Raman modes all show a similar trend as a function of Na substitution concentration (x). The changes are minimal and linear for x from 0 to ∼0.6 and deviate sharply for higher Na concentration (x > 0.6). These observations strongly suggest that the sublattice distortion in the A2B′B″X6 lattice arises due to a mismatch in the octahedra. This imparts a nonlinear change in the bandgap. Thus, a strong interplay between the [Ag(Na)Cl6]5− and [BiCl6]3– octahedra is shown to have a significant influence on the deviation of bandgap from Vegard's rule and further enforces the bandgap bowing effect in Cs2Ag1-xNaxBiCl6.

[1]  William W. Yu,et al.  Lead‐Free Halide Perovskites for Light Emission: Recent Advances and Perspectives , 2021, Advanced science.

[2]  R. Krahne,et al.  Phase Transitions in Low-Dimensional Layered Double Perovskites: The Role of the Organic Moieties , 2020, The journal of physical chemistry letters.

[3]  S. Chakraborty,et al.  ns2 Electron (Bi3+ and Sb3+) Doping in Lead-Free Metal Halide Perovskite Derivatives , 2020 .

[4]  M. Kanatzidis,et al.  Magnetizing lead-free halide double perovskites , 2020, Science Advances.

[5]  J. Zhang,et al.  Bandgap Engineering of Lead-Free Double Perovskite Cs2AgInCl6 Nanocrystals via Cu2+-Doping. , 2020, The journal of physical chemistry letters.

[6]  Zongping Shao,et al.  Recent Advances in Cs2AgBiBr6-Based Halide Double Perovskites as Lead-Free and Inorganic Light Absorbers for Perovskite Solar Cells , 2020 .

[7]  H. Ebert,et al.  The unique behavior of halide double perovskites with mixed halogens. , 2020, ACS applied materials & interfaces.

[8]  M. Marques,et al.  Advanced Raman spectroscopy of Cs2AgBiBr6 double perovskites and identification of Cs3Bi2Br9 secondary phases , 2020 .

[9]  Weiqiao Deng,et al.  Manganese-Doped, Lead-Free Double Perovskite Nanocrystals for Bright Orange-Red Emission , 2020, ACS central science.

[10]  Dan Huang,et al.  Highly Efficient Blue Emission from Self-Trapped Excitons in Stable Sb3+-Doped Cs2NaInCl6 Double Perovskites. , 2020, The journal of physical chemistry letters.

[11]  M. R. Wagner,et al.  Vibrational dynamics in lead halide hybrid perovskites investigated by Raman spectroscopy. , 2020, Physical chemistry chemical physics : PCCP.

[12]  A. Alam,et al.  Lattice Dynamics and Electron-Phonon Coupling in Lead-Free Cs2AgIn1-xBixCl6 Double Perovskite Nanocrystals. , 2020, The journal of physical chemistry letters.

[13]  Christopher J. Bartel,et al.  Inorganic halide double perovskites with optoelectronic properties modulated by sublattice mixing. , 2020, Journal of the American Chemical Society.

[14]  A. Pal,et al.  Bowing of transport gap in hybrid halide perovskite alloys (CH3NH3Sn1−xPbxI3): Which band is responsible? , 2020 .

[15]  P. Lin,et al.  Lead‐Free Double Perovskites for Perovskite Solar Cells , 2020, Solar RRL.

[16]  W. Mao,et al.  Tuning Emission and Electron–Phonon Coupling in Lead-Free Halide Double Perovskite Cs2AgBiCl6 under Pressure , 2019, ACS Energy Letters.

[17]  S. Sapra,et al.  Band Gap Engineering in Cs2(NaxAg1-x)BiCl6 Double Perovskite Nanocrystals. , 2019, The journal of physical chemistry letters.

[18]  P. Woodward,et al.  Cs2AgBiBr6−xClx solid solutions – band gap engineering with halide double perovskites , 2019, Journal of Materials Chemistry C.

[19]  A. Jen,et al.  On understanding bandgap bowing and optoelectronic quality in Pb–Sn alloy hybrid perovskites , 2019, Journal of Materials Chemistry A.

[20]  R. Palgrave,et al.  Anion Distribution, Structural Distortion, and Symmetry-Driven Optical Band Gap Bowing in Mixed Halide Cs2SnX6 Vacancy Ordered Double Perovskites , 2019, Chemistry of materials : a publication of the American Chemical Society.

[21]  Xiaolei Cui,et al.  Lead‐Free Cs2BiAgBr6 Double Perovskite‐Based Humidity Sensor with Superfast Recovery Time , 2019, Advanced Functional Materials.

[22]  Angshuman Nag,et al.  Initiation and future prospects of colloidal metal halide double-perovskite nanocrystals: Cs2AgBiX6 (X = Cl, Br, I) , 2018 .

[23]  Guangda Niu,et al.  Efficient and stable emission of warm-white light from lead-free halide double perovskites , 2018, Nature.

[24]  Guangda Niu,et al.  Photophysical Pathways in Highly Sensitive Cs2AgBiBr6 Double‐Perovskite Single‐Crystal X‐Ray Detectors , 2018, Advanced materials.

[25]  A. Walsh,et al.  Giant Electron-Phonon Coupling and Deep Conduction Band Resonance in Metal Halide Double Perovskite. , 2018, ACS nano.

[26]  X. Hou,et al.  High-Quality Cs2 AgBiBr6 Double Perovskite Film for Lead-Free Inverted Planar Heterojunction Solar Cells with 2.2 % Efficiency. , 2018, Chemphyschem : a European journal of chemical physics and physical chemistry.

[27]  A. Alam,et al.  Double Perovskites overtaking the single perovskites : A set of new solar harvesting materials with much higher stability and efficiency , 2018, 1801.07078.

[28]  Wenge Yang,et al.  High-Pressure Band-Gap Engineering in Lead-Free Cs2 AgBiBr6 Double Perovskite. , 2017, Angewandte Chemie.

[29]  D. Mitzi,et al.  Bandgap Engineering of Lead-Free Double Perovskite Cs2 AgBiBr6 through Trivalent Metal Alloying. , 2017, Angewandte Chemie.

[30]  W. Windl,et al.  Cs2AgBiX6 (X = Br, Cl): New Visible Light Absorbing, Lead-Free Halide Perovskite Semiconductors , 2016 .

[31]  Seongsu Lee,et al.  Insights into cationic ordering in Re-based double perovskite oxides , 2016, Scientific Reports.

[32]  Poul Georg Moses,et al.  Band bowing and band alignment in InGaN alloys , 2010 .

[33]  Haizhong Guo,et al.  Raman spectroscopy of ordered double perovskite La 2 Co Mn O 6 thin films , 2007 .

[34]  C. Howard.  Structures and phase transitions in perovskites--a group-theoretical approach. , 2005, Acta Crystallographica Section A Foundations of Crystallography.

[35]  Luis Morellón,et al.  Increase of Curie temperature in fixed ionic radius Ba$_\mathsf{1 + x}$Sr $_\mathsf{1-3x}$La$_\mathsf{2x}$FeMoO$_\mathsf{6}$ double perovskites , 2004 .

[36]  E. Haller,et al.  Origin of the large band-gap bowing in highly mismatched semiconductor alloys , 2003 .

[37]  M. Seong,et al.  The anomalous variation of band gap with alloy composition : cation vs anion substitution in ZnTe , 1999 .

[38]  Wladek Walukiewicz,et al.  Band Anticrossing in GaInNAs Alloys , 1999 .

[39]  D. J. Stufkens,et al.  Infrared and Raman spectra of the elpasolites Cs2NaSbCl6 and Cs2NaBiCl6: Evidence for a pseudo Jahn-Teller distorted ground state , 1990 .

[40]  Wei,et al.  Band gaps and spin-orbit splitting of ordered and disordered AlxGa1-xAs and GaAsxSb1-x alloys. , 1989, Physical review. B, Condensed matter.

[41]  G. Papatheodorou.  Raman spectroscopic studies of yttrium (III) chloride–alkali metal chloride melts and of Cs2NaYCl6 and YCl3 solid compounds , 1977 .