Rubidium Cations Research Articles

A New Type of Acidic OH-Groups in the LTL Zeolite

Acidic properties of ion-exchanged LTL zeolites have been studied using FTIR spectroscopy, complemented by X-ray powder diffraction, SEM-EDX, XRF and N2 physisorption. Infrared spectra of the ion-exchanged zeolites show the presence of two intense bands of the bridging OH-groups: a narrow band at ~3640 cm−1 that is attributed to Si(OH)Al groups freely vibrating in 12 MR and a broad, intense band at ~3250 cm−1 that is assigned to bridging OH groups forming hydrogen bond with neighbouring oxygen atoms, e.g., in six-membered rings. The former can be selectively removed by caesium or rubidium cations with up to 3 Cs+ or Rb+ per unit cell readily ion-exchanged into the LTL zeolite, replacing an equivalent number of acidic OH-groups or K+ cations within the structure. The cation migration of the larger cation, evaluated by the Rietveld refinement method, occurs mostly via the main 12 MR channels. By contrast, less than 1 Li+ or Na+ cation per unit cell can be introduced under similar conditions. Accordingly, the concentration of Si(OH)Al groups in back-exchanged NH4-K-LTL with smaller cations (Li+, Na+) does not differ considerably from the concentration of Brønsted acid sites in the original NH4-K-LTL. Lower concentrations of acid sites have been detected in the samples back-exchanged with Cs+, Rb+ and K+. In addition, the acidic properties of NH4-LTL samples have been compared with a structurally related NH4-MAZ zeolite.

Unraveling the cation dependent carrier cooling and transient mobility in lead-free A3Sb2I9 perovskites.

Lead halide perovskites (LHPs) have gained prominence for their exceptional photophysical properties, holding promise for applications in high-end optoelectronic devices. However, the presence of lead is one of the major obstacles to the commercialization of LHPs in the field of photovoltaics. To address this, researchers have explored environment friendly lead-free perovskite solar cells by investigating non-toxic perovskite materials. This study explores the enhancement of photophysical properties through chemical engineering, specifically cation exchange, focusing on the crucial photophysical process of hot carrier cooling. Employing femtosecond transient absorption spectroscopy and optical pump terahertz probe spectroscopy, we have probed the carrier relaxation dynamics in A3Sb2I9 with cesium and rubidium cations. This study unravels that the carrier relaxation is found to be slower in Rb3Sb2I9; along with this, the transient mobility decay is found to be retarded. Overall, this study suggests that an antimony-based Rb3Sb2I9 perovskite could be a substantial lead-free perovskite in photovoltaics. These findings provide valuable insights into cation engineering strategies, aiming to improve the overall performance of lead-free-based photovoltaic devices.

The physical attributes of rubidium-based Rb2TlRhF6 double perovskite halide: A first-principles investigation

Rubidium cations (Rb+) significantly improve the overall performance of organic-inorganic hybrid perovskite based devices and have gained exceptional attention due to their good thermal and structural stability. In this paper, we have evaluated the physical attributes of rubidium based Rb2TlRhF6 via DFT code using TB-mBJ potential. Structural stability has been confirmed through negative formation energy and calculated tolerance factor. Band structure and TDOS profile confirm semiconductor nature with 3.2 eV direct bandgap at (L-L) symmetry points. A ductile nature with metallic bonding is observed through the investigation of elastic attributes. Optical analysis of Rb2TlRhF6 indicates great absorption in the UV region. Low thermal conductivity and electrical resistivity, along with a high value for power factor, resulted in high ZT value of 0.8 and 800 K. The combined qualities provide a stunning and exciting picture of this compound for use in thermoelectric advanced technologies.

Trifunctional Rb+-Intercalation Enhancing the Electrochemical Cyclability of Ammonium Vanadate Cathode for Aqueous Zinc Ion Batteries.

Rechargeable aqueous zinc-ion batteries (AZIBs) have been highly desired due to their low cost, intrinsic safety, environmental friendliness, and great potential in large-scale power storage systems. However, their practical applications are impeded by unstable long-term electrochemical performances induced by microstructure degradation of the cathode material, hydrogen evolution reaction in the electrolyte, and dendritic growth on the zinc anode upon cycling. In this work, rubidium cations (Rb+) are introduced to synthesize an Rb+-preintercalated NH4V4O10 (NVO-Rb) composite. The contribution of Rb+ ions as pillars in V-O interlayers to facilitating Zn2+ storage is investigated first, and then the influences of partial Rb+ ions from the NVO-Rb cathode on the aqueous electrolyte and zinc anode are specially inspected from different viewpoints. Based on a series of characterization results, it is comprehensively elucidated that the partial Rb+ ions into the electrolyte suppress the generation of byproducts on the cathode and regulate the dendrite growth on the zinc anode, thus effectively promoting the long-term electrochemical performances of NVO-based AZIBs. The assembled Zn∥Zn(CF3SO3)2∥NVO-Rb cell can exhibit a high specific capacity and optimized Zn2+ diffusion kinetics, especially an improved electrochemical cyclability with a capacity retention of 87.6% at 5 A g-1 over 10000 cycles. This study enlightens the multiple roles of cation-preintercalation in the layered structure material and provides a feasible strategy for the development of high-performance aqueous batteries.

Strain Regulation of Mixed-Halide Perovskites Enables High-Performance Wide-Bandgap Photovoltaics.

Wide-bandgap mixed-halogen perovskite materials are widely used as top cells in tandem solar cells. However, serious open-circuit voltage (Voc ) loss restricts the power conversion efficiency (PCE) of wide-bandgap perovskite solar cells (PSCs). Herein, it is shown that the resulting methylammonium vacancies induce lattice distortion in methylammonium chloride-assisted perovskite film, resulting in an inhomogeneous halogen distribution and low Voc . Thus, a lattice strain regulation strategy is reported to fabricate high-performance wide-bandgap PSCs. Rubidium (Rb) cations are introduced to fill the A-site vacancy caused by the methylammonium volatilization, which alleviates shrinkage strain of the perovskite crystal. The reduced lattice distortion and increased halide ion migration barrier result in a homogeneous mixed-halide perovskite film. Due to improved carrier transport and suppressed nonradiative recombination, the Rb-treated wide-bandgap PSC (1.68eV) achieves an excellent PCE of 21.72%, accompanied by a high Voc of 1.22V. The resulting device maintains more than 90% of its initial PCE after 1500h under 1-sun illumination conditions.

Dual Functionalities of Rb Cation in Lean Electrolyte Lithium Sulfur Batteries

Achieving large discharge capacity and high cycling stability under high sulfur loading and lean electrolyte condition is critical for practical lithium sulfur batteries. However, it is impeded by the large overpotential for lithium sulfide (Li2S) nucleation at the cathode, caused by the sluggish reduction kinetics of lithium polysulfide and the short-circuit triggered by inhomogeneous Li electroplating at the anode. In this study, we report that adding rubidium cation to lean electrolyte in an additive level (0.05 M) can address the two challenges owing to the modifications of the cathode and anode surfaces by the formation of rubidium sulfide. At the sulfur cathode, the rubidium sulfide acts as a catalyst, accelerating the reduction of lithium polysulfides. At the Li metal anode, a rubidium sulfide-enriched inner SEI quickly passivates the surface, suppressing electrolyte decomposition and promoting uniform lithium deposition due to its lithiophilicity. The drop-in-solution leads to impressive results, delivering more than 3 mAh cm−2 over approximately 80 cycles at a sulfur loading of 3.8 mgsulfur cm−2 and an electrolyte to sulfur ratio of 3 μl mg−1.

Stable Yellow Light-Emitting Diodes Based on Quasi-Two-Dimensional Perovskites.

Perovskite light-emitting diodes (PeLEDs) show great potential in display and lighting because of their tunable wavelength, narrow emission bandwidths, and high color purity. Currently, the external quantum efficiency (EQE) of red and green PeLEDs has reached >23%. However, yellow PeLEDs are still rarely reported because of phase separation in mixed-halide perovskites and the coexistence of multiple phases in quasi-two-dimensional (quasi-2D) perovskites L2An-1BnX3n+1 (n = 1, 2, 3, ...), where L is a bulky organoammonium ligand. Here, we fabricate stable yellow PeLEDs by manipulating the phase distribution and incorporating rubidium cations (Rb+) in quasi-2D perovskites. The transient absorption results confirm that alkylammonium ligand butyl ammonium (BA) has a narrower phase distribution than phenylethyl ammonium (PEA) in the quasi-2D perovskites, resulting in a more blue-shifted emission peak. We further incorporate a proper molar ratio of Rb+ in the (BA)2CsPb2I7 perovskite to blue-shift the emission peak to the yellow range. Finally, the yellow PeLEDs exhibit an EQE of 3.5%, and the stable emission peak is located at 595 nm. Our work provides a useful approach for the fabrication of highly efficient and stable yellow PeLEDs.

Biochemical and structural insights into an unusual, alkali-metal-independent S-adenosyl-L-homocysteine hydrolase from Synechocystis sp. PCC 6803.

The mesophilic cyanobacterium Synechocystis sp. PCC 6803 encodes an S-adenosyl-L-homocysteine hydrolase (SAHase) of archaeal origin in its genome. SAHases are essential enzymes involved in the regulation of cellular S-adenosyl-L-methionine (SAM)-dependent methylation reactions. They are usually active as homotetramers or, less commonly, as homodimers. A SAHase subunit is composed of two major domains: a cofactor (NAD+)-binding domain and a substrate (S-adenosyl-L-homocysteine)-binding domain. These are connected by a hinge element that is also a coordination site for an alkali-metal cation that influences domain movement during the catalytic cycle. Typically, the highest activity and strongest substrate binding of bacterial SAHases are observed in the presence of K+ ions. The SAHase from Synechocystis (SynSAHase) is an exception in this respect. Enzymatic and isothermal titration calorimetry studies demonstrated that in contrast to K+-dependent SAHases, the activity and ligand binding of SynSAHase are not affected by the presence of any particular alkali ion. Moreover, in contrast to other SAHases, the cyanobacterial enzyme is in an equilibrium of two distinct oligomeric states corresponding to its dimeric and tetrameric forms in solution. To explain these phenomena, crystal structures of SynSAHase were determined for the enzyme crystallized in the presence of adenosine (a reaction byproduct or substrate) and sodium or rubidium cations. The structural data confirm that while SynSAHase shares common structural features with other SAHases, no alkali metal is coordinated by the cyanobacterial enzyme as a result of a different organization of the macromolecular environment of the site that is normally supposed to coordinate the metal cation. This inspired the generation of SynSAHase mutants that bind alkali-metal cations analogously to K+-dependent SAHases, as confirmed by crystallographic studies. Structural comparisons of the crystal structure of SynSAHase with other experimental models of SAHases suggest a possible explanation for the occurrence of the cyanobacterial enzyme in the tetrameric state. On the other hand, the reason for the existence of SynSAHase in the dimeric state in solution remains elusive.

Polyoxomolybdate Layered Crystals Constructed from a Heterocyclic Surfactant: Syntheses, Pseudopolymorphism and Introduction of Metal Cations.

Crystals with layered structures are crucial for the construction of functional materials exhibiting intercalation, ionic conductivity, or emission properties. Polyoxometalate crystals hybridized with surfactant cations have distinct layered packings due to the surfactants which can form lamellar structures. Introducing metal cations into such polyoxometalate-surfactant hybrid crystals is significant for the addition of specific functions. Here, polyoxomolybdate–surfactant hybrid crystals were synthesized as single crystals, and unambiguously characterized by X-ray structure analyses. Octamolybdate ([Mo8O26]4–, Mo8) and heterocyclic surfactant of 1-dodecylpyridinium (C12py) were employed. The hybrid crystals were composed of α-type and β-type Mo8 isomers. Two crystalline phases containing α-type Mo8 were obtained as pseudopolymorphs depending on the crystallization conditions. Crystallization with the presence of rubidium and cesium cations caused the formation of metal cation-introduced hybrid crystals comprising β-Mo8 (C12py-Rb-Mo8 and C12py-Cs-Mo8). The yield of the C12py-Rb-Mo8 hybrid crystal was almost constant within crystallization temperatures of 279–303 K, while that of C12py-Cs-Mo8 decreased over 288 K. This means that the C12py-Mo8 hybrid crystal can capture Rb+ and Cs+ from the solution phase into the solids as the C12py-Rb-Mo8 and C12py-Cs-Mo8 hybrid crystals. The C12py-Mo8 hybrid crystals could be applied to ion-capturing materials for heavy metal cation removal.

Interpretation of Rubidium-Based Perovskite Recipes toward Electronic Passivation and Ion-Diffusion Mitigation.

Rubidium cation (Rb+ ) addition is witnessed to play a pivotal role in boosting the comprehensive performance of organic-inorganic hybrid perovskite solar cells. However, the origin of such success derived from irreplaceable superiorities brought by Rb+ remains ambiguous. Herein, grain-boundary-including atomic models are adopted for the accurate theoretical analysis of practical Rb+ distribution in perovskite structures. The spatial distribution, covering both the grain interiors and boundaries, is thoroughly identified by virtue of synchrotron-based grazing-incidence X-ray diffraction. On this basis, the prominent elevation of the halogen vacancy formation energy, improved charge-carrier dynamics, and the electronic passivation mechanism in the grain interior are expounded. As evidenced by the increased energy barrier and suppressed microcurrent, the critical role of Rb+ addition in blocking the diffusion pathway along grain boundaries, inhibiting halide phase segregation, and eventually enhancing intrinsic stability is elucidated. Hence, the linkage avalanche effect of occupied location dominated by subtle changes in Rb+ concentration on electronic defects, ion migration, and phase stability is completely investigated in detail, shedding a new light on the advancement of high-efficiency cascade-incorporating strategies and perovskite compositional engineering.

Crystal Structure and Energetics of Arsenic(III)-Oxide Intercalates with Rubidium Chloride and Their Comparison with Isostructural Intercalates of Potassium Halides

Two intercalation compounds of arsenic(III) oxide and rubidium chloride have been crystallized and characterized. The first, anhydrous RbCl·2As2O3 (PRbCl), crystallizes in space group P6/mmm with cell parameters a = 5.23520(16) Å and c = 9.0495(4) Å, and it is isostructural with anhydrous intercalates of arsenic(III) oxide with potassium halides. The second one, RbCl·As2O3·1/2H2O (Y′RbCl), crystallizes in space group P6/mmm with a = 5.25072(17) Å and c = 12.6472(5) Å, and its crystal structure is very similar to that of KCl·As2O3·1/2H2O. In the case of a large single crystal of compound Y′RbCl, weak satellite reflections were observed. The commensurate superstructure that gives rise to them has been described using the supercell approach (a = 9.019(4) Å, c = 12.6433(7) Å) and briefly discussed. The structures of intercalates PRbCl and Y′RbCl have been studied by 87Rb solid-state magic-angle spinning nuclear magnetic resonance (ssNMR) spectroscopy which has indicated the presence of one and two rubidium cations with distinct chemical environments, respectively. The comparison of these spectra allowed for the assignment of peaks to rubidium cations occupying particular sites. Infrared (IR) spectra and 1H ssNMR spectra of intercalate Y′RbCl have revealed dynamic disorder of water molecules occurring on the time scale of the IR experiment. Last but not least, interlayer interaction energies as well as thermodynamic stability of intercalate PRbCl and isostructural arsenic(III)-oxide intercalates with potassium halides have been studied computationally in the framework of density functional theory. Results of the calculations indicate that an increase in the size of anions or cations leads to an increase in the stability of the obtained intercalates.

A New Modification of Rb[Al(NH2)4] and Condensation in Solid State

A new modification of Rb[Al(NH2)4] in space group C2/c, which differs from the known structural modification in the way the [Al(NH2)4]−-tetrahedra are arranged in the surrounding area of the rubidium cation, was obtained from ammonothermal synthesis at 673 K and 680 bar. The crystal structure was determined by Rietveld refinements and further investigated by infrared and Raman spectroscopy. Thermal gravimetric investigations indicate two decomposition steps up to 450 °C, which can be assigned to ammonia leaving the material while the sample liquefies. During the third and final step, volatile rubidium amide is released, leaving nano-scaled cubic AlN behind. Investigating differently aged samples implies decomposition and condensation of amidoaluminate ions already at ambient temperature, which is supported by refinements of single crystal X-ray diffraction data, revealing lower nitrogen amounts than expected. The observed single crystal also exhibits a significantly smaller volume than the reported structures, further supporting the decomposition–condensation mechanism.

In situ NMR Investigation of the Photoresponse of Perovskite Crystal

Summary Hybrid perovskites are outstanding candidates for use in optoelectronic devices. Nonetheless, hybrid perovskites present numerous fundamental issues that are not yet fully understood. This study seeks to address this problem by reporting on the occurrence of ultraslow dynamic orientation changes in the methylammonium (MA) cations and the corresponding changes in the inorganic lattice of MAPbI3 perovskite crystals occurring over a time scale of 100 s under continuous illumination based on in situ single-crystal 2H nuclear magnetic resonance and in situ X-ray diffraction results. The demonstrated ultraslow dynamic changes in MAPbI3 are far slower than elementary molecular motions typically having time scales of femtoseconds and picoseconds and have never been reported previously. The ultraslow dynamic changes have been correlated with the reduction of band gap and the increase of absorption coefficient of MAPbI3, providing the molecular origins of the stabilization process in the photoresponse of the MAPbI3 device.

Hirshfeld surface analysis and IR investigation for the rubidium hexaaquacopper(II) selenate

Abstract The Tutton's salt, Rb2[Cu(H2O)6](SeO4)2 was grown by slow evaporation at room temperature. It crystallizes in the monoclinic space group P21/c. The unit cell dimensions are: a = 6.363(2) A, b = 12.431(4) A, c = 9.373(4) A, α = γ = 90.00°, β = 104.33(4)°, V = 718.3(5) A3 and Z = 2. The crystals are composed of isolated Cu(H2O)6 octahedral and SeO4 tetrahedrons connected by hydrogen bonds and rubidium cations. The infrared spectra of rubidium hexaaquacopper(II) selenate are presented and discussed. In order to know the intermolecular interactions in the Rb2[Cu(H2O)6](SeO4)2, the analysis of the Hirshfeld surface (HS) and its fingerprint plots was applied.

A‐Site Rubidium Cation‐Incorporated CsPbI2Br All‐Inorganic Perovskite Solar Cells Exceeding 17% Efficiency

Due to its excellent thermal stability and high performance, inorganic cesium lead mixed halide (ABX3, where A = Cs, B = Pb, and X = I/Br) all‐inorganic perovskite solar cells (IPVSCs) have attracted much interest in optoelectronic applications. However, the film quality, enough absorption by desired film thickness, and nature of partial replacement of cations determine the stability of the CsPbI2Br perovskite films. Herein, a hot air method is used to control the thickness and morphology of the CsPbI2Br perovskite thin film, and the A‐site (herein, Cs+) cation is partially incorporated by rubidium (Rb+) cations for making the stable black phase under ambient conditions. The Rb cation‐incorporated Cs1−xRbxPbI2Br (x = 0–0.03) perovskite thin films exhibit high crystallinity, uniform grains, extremely dense, and pinhole‐free morphology. The fabricated device with its Cs0.99Rb0.01PbI2Br perovskite composition with poly(3‐hexylthiophene‐2,5‐diyl) as a hole‐transporting layer exhibits a power conversion efficiency (PCE) of 17.16%, which is much higher than that of CsPbI2Br‐based IPVSCs. The fabricated Cs0.99Rb0.01PbI2Br‐based IPVSC devices retain >90% of the initial efficiency over 120 h at 65 °C thermal stress, which is much higher than that of CsPbI2Br samples.

Impact of Cesium/Rubidium Incorporation on the Photophysics of Multiple‐Cation Lead Halide Perovskites

Incorporating cesium (Cs) or rubidium (Rb) cations into multiple‐cation lead mixed halide perovskites (FA0.83MA0.17Pb(I0.83Br0.17)3) increases their photovoltaic performance. Herein, the fundamental photophysics of perovskites are investigated by steady‐state and transient optical spectroscopy and the reasons for the performance increase are revealed. Cs/Rb‐cation incorporation slightly increases the bandgap, whereas exciton binding energies remain in the range of a few meV. Urbach energies are reduced, suggesting improved perovskite microstructure upon Cs/Rb incorporation. Carrier density‐induced broadening of the photo‐bleaching following the Burstein–Moss model is observed, and the effective carrier masses are determined to be a few tenths of the electron rest mass. From fits of the high‐energy tail of the perovskite's photo bleach to Boltzmann's distribution, subpicosecond hot‐carrier cooling is revealed, implying strong carrier–phonon coupling. Importantly, the charge carrier recombination dynamics indicate that Cs/Rb‐incorporation reduces both the first‐order (trap‐assisted) and the second‐order (radiative) recombination, which appears to be the main reason for the observed performance increase upon Cs/Rb‐cation incorporation. Overall, this work presents a detailed study of the photophysics of multiple‐cation mixed halide lead perovskites and develops a concise picture of the impact of cesium/rubidium incorporation on the photophysics and device performance.

Synthesis, Crystal Structure, and Hirshfeld Surface Analysis of Rubidium trans-Bis(N-methyliminodiacetato)chromate(III)

A new rubidium salt, Rb[Cr(C5H7NO4)2] (C5H7NO4 = mida, methyliminodiacetate), was prepared and its molecular structure was determined from synchrotron X-ray data at 173 K. The complex crystallizes in the space group C2/c of the monoclinic system with four mononuclear formula units in a cell with dimensions a = 16.905(3) A, b = 6.483(2) A, c = 13.906(3) A, and β = 113.95(3)°. The Cr atom is located in a center of symmetry with one independent Cr–N bond length of 2.081(2) A and two Cr–O bond lengths of 1.9534(18) and 1.9628(18) A. The Cr(III) ion is coordinated by two N atoms and four O atoms of symmetrical-facial mida ligands, displaying a distorted octahedral geometry. Hirshfeld surface analysis with 2D fingerprint plots revealed that the O···H, H···H, and O···Rb interactions are the main intermolecular interactions. The crystal structure is stabilized by the O···H, H···H, and O···Rb interactions among rubidium cation, the H atoms and the O atoms of carboxylate group from neighboring mida groups.

Rubidium tetrafluoridobromate(III): redetermination of the crystal structure from single-crystal X-ray diffraction data

Single crystals of rubidium tetrafluoridobromate(III), RbBrF4, were grown by melting and recrystallizing RbBrF4 from its melt. This is the first determination of the crystal structure of RbBrF4 using single-crystal X-ray diffraction data. We confirmed that the structure contains square-planar [BrF4]− anions and rubidium cations that are coordinated by F atoms in a square-antiprismatic manner. The compound crystallizes in the KBrF4 structure type. Atomic coordinates and bond lengths and angles were determined with higher precision than in a previous report based on powder X-ray diffraction data [Ivlev et al. (2015). Z. Anorg. Allg. Chem. 641, 2593–2598].

Synthesis of giant Mo2O2S2-containing seleno-tungstate architectures: New multisite cation receptors

Self-assembly reaction in the system containing Na2WO4, SeO32− and binuclear oxothiocation [Mo2O2(μ-S)2(H2O)6]2+ results in the formation of a nano-sized hybrid ChalcoPOM anionic complex [(W16Se2O58(H2O)2)4(W2O5)2(W4O13)2(Mo2O2(μ-S)2(H2O)2)4(Mo2O2(μ-S)2(SeO3))4]40−. The complex can be isolated as Na+/K+ salt (NaK-1) by slow evaporation of the mother liquor or Rb+ salt after addition of RbBr. Recrystallization of the Rb salt from 1 M LiCl gives red crystals of Rb17Li23[(W16Se2O58(H2O)2)4(W2O5)2(W4O13)2(Mo2O2(μ-S)2(H2O)2)4(Mo2O2(μS)2 (SeO3))4]∙120H2O (Rb-1), which was characterized by XRD, IR, TGA, and elemental analysis. Rubidium cations are encapsulated into two large cavities inside the anion which differ from the cavities in which are embedded Na+ cations.

Improvement of Cs2AgBiBr6 double perovskite solar cell by rubidium doping

Cs 2 AgBiBr 6 having a double perovskite structure is expected to achieve non-lead and stable optoelectronic devices, and has received wide attention recently. A strategy for improving of perovskite films via Rubidium cation (Rb + ) is for the first time reported. When Rb + was incorporated into Cs 2 AgBiBr 6 to form (Cs 1-x Rb x ) 2 AgBiBr 6 , the absorption at long wavelength was enhanced and the density of defect state was reduced without changing the crystal lattice. Furthermore, the mechanism of Rb + doping to improve double perovskites and the optimal doping ratio was studied in this report. The average power conversion efficiency of doped devices is nearly 15% higher than that of standard devices from 20 devices of each group. Moreover, in the champion device, the power conversion efficiency achieved 1.52% with a high fill factory of 0.788. • Rubidium was incorporated into the double perovskite material. • The first report proves that the performance of Cs 2 AgBiBr 6 solar cells can be improved by doping rubidium. • The average PCE of the devices was increased by 15% after doping.