Perovskite Solid Solutions Research Articles

Insights into the structural, dielectric, optical and electrochemical characteristics reveal the limiting parameters toward efficient OER catalysts in the perovskite solid solution Sr1-xLaxTi1-xFexO3 (0.2 ≤ x ≤ 0.8)

Due to their structural stability and flexibility, perovskite oxides have paved their way as oxygen evolution reaction (OER) electrocatalysts. The in-depth understanding of the limiting factors toward good activity and fast charge transfer are still considered as major challenges for highly active OER perovskite catalysts. In this work, we disclose the changes in the perovskite structure and properties that influence the activity as we introduce new criteria to be considered for perovskites electrocatalysts design. The activity test of the series Sr1-xLaxTi1-xFexO3 (0.2 ≤ x ≤ 0.8) reveals the overpotential of 300 mV @ 10 mA.cm−1, and Tafel slop of 57.6 mV dec−1, as the lowest values corresponding to the composition x = 0.4. As function of the composition, the dielectric constant is found to decrease from 3000 (x = 0.2) to 953 (x = 0.4), and increases up to 5497 (x = 0.8). This variation of the dielectric constant is found to influence the activity of the catalysts where lowest overpotential of 300 mV @ 10 mA.cm−1 is found for x = 0.4 with the smallest dielectric constant. The phase transition detected in the perovskite series upon substitution has induced a distortion in the unit cell, which is found to be in alignment with the evolution of the overpotential in the perovskites series. The distortion has induced a preferable octahedra orientation for efficient OER reaction, this orientation correspond to the interatomic distance <Ti/Fe-O2> (1) = 1.89 Å and <Ti/Fe-O2> (2) = 2.04 Å (x=0.4) with the condition of <Ti/Fe-O2> (1) remains shorter than <Ti/Fe-O2> (2). The band gap, thus the conduction and valence bands edges, is found to decrease with the increase of the interatomic distance (Fe/Ti-O) and with the deviation of the Bond angle (B)-O2-(B) from the ideal value of 180°. These findings put light on the limiting factors of the perovskites activity by linking the structural parameters and the physical properties with the objective of accurately designing highly-efficient perovskite OER electrocatalysts.

Accelerated discovery of perovskite solid solutions through automated materials synthesis and characterization

Accelerating perovskite solid solution discovery and sustainable synthesis is crucial for addressing challenges in wireless communication and biosensors. However, the vast array of chemical compositions and their dependence on factors such as crystal structure, and sintering temperature require time-consuming manual processes. To overcome these constraints, we introduce an automated materials discovery approach encompassing machine learning (ML) assisted material screening, robotic synthesis, and high-throughput characterization. Our proposed platform for rapid sintering and dielectric analysis streamlines the characterization of perovskites and the discovery of disordered materials. The setup has been successfully validated, demonstrating processing materials within minutes, in stark contrast to conventional procedures that can take hours or days. Following setup validation with established samples, we showcase synthesizing single-phase solid solutions within the barium family, such as (BaxSr1-x)CeO3, identified through ML-guided chemistry.

CaTiO3 nanoparticles as functional additives for the BaTiO3-based X8R type dielectric ceramics

This research investigates the potential of Calcium titanate (CaTiO3 or CT) nanoparticles as functional additives to enhance the dielectric properties of Barium titanate (BaTiO3 or BT)-based ceramic dielectrics. To address the need for high-temperature stability in MLCC (multilayer ceramic capacitor) applications, especially within the automotive and aerospace sectors, we have explored BT-based complex perovskite solid solutions comprising various cation substitutions, including Ca2+ and Yb3+, into barium titanate (BT) as a method to suppress the dielectric property anomaly near the Curie temperature effectively. The focus is on the impact of the application of CT nanoparticles as additive materials on phase formation, microstructure development, and dielectric behavior of the resulting ceramics to align with the Extended 'Temperature Coefficient of Capacitance (TCC)' criteria defined by the EIA X8R specification. When the hydrothermally synthesized CT nanopowder was applied in the Ca-doped BT ceramics fabrications as source material of the Ca dopants, it was beneficial to achieve both temperature stability and high dielectric constant. The CT nanoparticles are believed to play multiple roles during the solid-state reaction with BT and rare earth dopant (Yb). Since the Yb3+ ions can be more easily dissolved into the CT lattice than BT with their amphoteric character, the CT nanoparticles in the BT-CT-Yb2O3 mixture can act as an intermediary, dissolving the Yb3+ first in its A- or B-site before the final solid-solution formation with the BT. The sequential substitutions of the Yb3+ and Ca2+ into BT via CT nanoparticles could affect the site occupancy of Ca2+ in the BT lattice, which is very important in determining the dielectric properties of the Ca-doped BT processed in reducing atmospheres. Through a comprehensive experimental approach, including phase composition analysis via X-ray diffraction (XRD) and microstructural examination using Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM), this work reveals the significance of synthetic methodology and dopant incorporation strategy on achieving a desired core-shell microstructure and improved dielectric performance. This research underscores the efficacy of CT nanoparticles as a promising route towards the development of BT-based dielectric ceramics with superior temperature stability, offering valuable insights for the advancement of MLCC technology to cater to high-temperature applications.

Three Perovskite Phases with Different Cation Orders in Sm2MnMn(Mn4-xSbx)O12.

Cation order, which can be controlled by synthesis conditions and stoichiometry, plays an important role in properties of perovskite materials. Here we show that aliovalent doping by Sb5+ in Sm2MnMn(Mn4-xSbx)O12 quadruple perovskite solid solutions can control cation orders in both A and B sites. Samples with 0.4≤x≤2 were synthesized by a high-pressure, high-temperature method at 6 GPa and 1770 K. Three regions with different cation orders were found at 0.5≤x≤1.0, x=1.5-1.6, and x=1.8. The 0.5≤x≤1.0 compositions have a B-site-disordered and A-site columnar-ordered structure with space group P42/nmc; the x=1.5 and 1.6 samples have a B-site rock-salt-ordered and A-site columnar-ordered structure with space group P42/n; the x=1.8 sample has a B-site rock-salt-ordered and A-site-disordered structure with space group P21/n. All the samples show one ferrimagnetic transition: TC increases from 35 K to 73 K for 0.5≤x≤1.0, TC=81 K for x=1.5 and 1.6, and TC=53 K for x=1.8.

Broadband dielectric spectroscopy of a PbHf1-xSnxO3 material

ABSTRACT The combination of PbHfO3 and PbSnO3 in perovskite solid solutions presents valuable opportunities to study the formation mechanisms of incommensurate phases. Crystals of PbHf1-xSnxO3 with 8% Sn were grown and measured using broadband dielectric spectroscopy to investigate the nature of relaxation and the effects of phase transitions. Our findings reveal significant alterations in the dielectric response of the PbHf0.92Sn0.08O3 solid solution, shedding light on the influence of Sn doping on lattice dynamics during the phase transition.

Polarization- and stress-related lattice dynamics in solid-solution perovskite ferroelectrics

Perovskite ferroelectrics play an essential role in modern science and technology. The excellent properties of perovskites are closely related to their lattice dynamics. Potassium tantalate niobate (KTa1-xNbxO3, abbreviated as KTN) is a typical solid-solution perovskite with superior properties. Although the optical and electrical performances of KTN crystals have been widely explored, information on their lattice dynamics is still scarce, which partially limits the research and performance optimization of KTN. As a solid-solution, spontaneous polarization of KTN exhibits strong tunability, and there is stress within KTN. Here, we performed first-principles calculations in conjunction with experiments to investigate the polarization- and stress-related lattice dynamics in KTN. We assigned the vibration modes of observed Raman peaks, and established the relationship between spontaneous polarization and vibration. Especially, the lattice dynamics evolution of KTN crystal under stress was investigated. And the results provide insights into the regulatory effect of stress on dielectric property from the perspective of lattice dynamics. Finally, the variation trends of phonons under stress, as well as the mechanism of stress effect in tetragonal perovskites were explained. The conclusions drawn for KTN crystal were generalized to tetragonal ferroelectric systems. Our results help to reflect spontaneous polarization and structural characteristics distribution through non-destructive Raman spectra, and give a reference for improving performance by regulating lattice dynamics. The findings will hopefully guide research on performance origin and refined design of perovskite functional materials.

Crystal Growth and Structural and Optical Characterizations of Mixed-Cation MA1-xCsxPbBr3 Halide Perovskite Solid Solutions

Photovoltaic devices fabricated using mixed-cation halide perovskites have demonstrated a superior combination of high efficiency and long operating life. In this study, we synthesize a series of mixed-cation halide perovskites with the composition of MA1-xCsxPbBr3 (MA= CH3NH3), where x varies from 0 to 1. We carefully examine various polar solvents and develop a relatively facile, room temperature solution-based growth method for growing these single crystals under optimal conditions. We conduct a comprehensive investigation of the influence of the Cs+ cation on the structure and optical properties of the perovskite solid solutions. The structural characterization using X-ray diffraction confirms the successful substitution of cesium for the methylammonium (MA) cation in the MA1-xCsxPbBr3 perovskite structure, with a continuous solubility. As the Cs+ content increases, the crystal structure undergoes a gradual transformation from a cubic phase (for MAPbBr3) to an orthorhombic phase (for CsPbBr3). To study the impact of Cs substitution on their optical properties, we perform UV-Vis absorption analysis, and find no significant change in the bandgap value, which remains approximately 2.12 - 2.14 eV for the compositions with x up to 0.7, and for x &gt; 0.7, however, the bandgap value gradually increases to reach 2.21 eV for pure CsPbBr3. This work demonstrates a valid technique for the growth of halide perovskite solid solution crystals, which can be a versatile tool for tailoring the structure, long-term stability, and optoelectronic properties for advanced photovoltaic applications.

Structure and equation of state of Ti-bearing davemaoite: new insights into the chemical heterogeneity in the lower mantle

Abstract Davemaoite (CaSiO3 perovskite) is considered the third most abundant phase in the pyrolytic lower mantle and the second most abundant phase in the subducted mid-ocean ridge basalt (MORB). During the partial melting of the pyrolytic upper mantle, incompatible titanium (Ti) becomes enriched in the basaltic magma, forming Ti-rich MORB. Davemaoite is considered an important Ti-bearing mineral in subducted slabs by forming a Ca(Si,Ti)O3 solid solution. However, the crystal structure and compressibility of Ca(Si,Ti)O3 perovskite solid solution at relevant pressure and temperature conditions were not systematically investigated. In this study, we investigated the structure and equations of state of Ca(Si0.83Ti0.17)O3 and Ca(Si0.75Ti0.25)O3 perovskites at room temperature up to 82 GPa and 64 GPa, respectively, by synchrotron X-ray diffraction (XRD). We found that both Ca(Si0.83Ti0.17)O3 and Ca(Si0.75Ti0.25)O3 perovskites have a tetragonal structure up to the maximum pressures investigated. Based on the observed data and compared to pure CaSiO3 davemaoite, both Ca(Si0.83Ti0.17)O3 and Ca(Si0.75Ti0.25)O3 perovskites are expected to be less dense up to the core-mantle boundary (CMB), and specifically ~1-2 % less dense than CaSiO3 davemaoite in the pressure range of the transition zone (15-25 GPa). Our results suggest that the presence of Ti-bearing davemaoite phases may result in a reduction in the average density of the subducting slabs, which in turn promotes their stagnation in the lower mantle. The presence of low-density Ti-bearing davemaoite phases and subduction of MORB in the lower mantle may also explain the seismic heterogeneity in the lower mantle, such as large low shear velocity provinces (LLSVPs).

Achieving high energy storage density at low operating fields in lead hafnate-based novel perovskite solid solutions

Schematic diagram illustrating the concept, approaches and goal in the design and preparation of a new solid solution system (1 − x)PbHfO3–xAgNbO3, with enhanced maximum polarization and recoverable energy storage density at low operating fields.

Organic cations in halide perovskite solid solutions: exploring beyond size effects.

Halide perovskites are a class of materials of consolidated optoelectronic and electrochemical applications, reaching efficiencies compared to established materials in respective fields. In this scenario, the design and understanding of composition-structure-property relations is imperative. In solid solutions containing mixed cations, some direct relations between the sizes of the substituents and the properties of perovskites are generally observed. However, in several cases, these relations are not observed, implying that other characteristics of these cations play a major role. Despite its importance, this understanding has not been comprehensively deepened. To address this issue, we synthesized and characterized the structure, electrical behavior, and stability of methylammonium lead iodide-based perovskites with equal amounts of the substituents guanidinium, ethylammonium, and acetamidinium. These three large organic cations have essentially equal sizes but other remarkably different characteristics, such as the number of N-H bonds, intrinsic dipole moment, and order of C-N bonds. Herein, we show that these cations have dramatically different effects over important fundamental and applied properties of resulting perovskites, including the orthorhombic-to-tetragonal and tetragonal-to-cubic phase transitions, microstructural development, ionic conductivity, I-V hysteresis, electronic carrier mobility, and stability against light-induced degradation. These effects are correlated with the characteristics of the large substituent cations and help pave the way for a better rational chemical design of halide perovskites.

Significant improvement in energy storage for BT ceramics via NBT composition regulation

Dielectric ceramic capacitors play an important part in modern electronics, but the adoption of environmentally friendly lead-free ceramics is often limited by their inferior energy storage efficiency (η) and density (Wrec). One novel ceramic composition, (1-x)(Ba0.7Sr0.3)(Zr0.2Ti0.8)O3-xNa0.5Bi0.5TiO3 (BSZT-NBT, x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) was designed to achieve large max polarization (Pmax) and outstanding energy storage performance (ESP). Structural analyses indicate that BSZT-NBT ceramics form stable perovskite solid solutions. Dielectric properties testing confirms the enhanced relaxor behavior. Remarkably, the BSZT-NBT (x = 0.5) ceramics exhibit superb ESP, including ultrahigh η of 94.9%, elevated Wrec of 4.45 J·cm–3, large Pmax of 38.01 μC·cm–2. Furthermore, these ceramics demonstrate excellent temperature and frequency stability for ESP. Charge-discharge performance at room temperature and 120 kV·cm–1 showcases excellent Wdis, t0.9 and PD of 0.64 J·cm–3, 69.8 ns and 48 MW·cm–3, respectively. Our results indicate that the introduction of NBT effectively improves the Pmax and ESP of BT-based ceramics. The BSZT-NBT ceramics hold promise for addressing the limitations of lead-free ceramic capacitors and advancing their practical applications in electronic devices.

Structure, magnetic and electrical properties of Tb0.5Nd0.5CoO3 perovskite solid solutions with carbon material flakes (CMF)

In this paper, we study the ceramics of cobaltite [Tb0.5Nd0.5CoO3]1−yCy with equiatomic contents of terbium and neodymium and with the addition of a carbon material flakes (СMF) with the content of carbon in the range of weight fraction 0 < y < 0.01. The ceramics were obtained by the method of solid-phase reactions according to the standard ceramic technology in air. Using X-ray diffraction and energy-dispersive analysis, it was established that the initial (undoped) solid solution is single-phase with perovskite structure. It was shown that Co3+ ions in undoped ceramics under study are in a non-magnetic low-spin state over the entire temperature range under consideration (2–320 K), and the entire contribution to the magnetization is due to Tb3+ and Nd3+ ions. An analysis of the temperature dependences of the electrical resistance R(T) shows that the initial solid solution behaves like a dielectric with a reduced activation energy of about 0.3–0.35 eV in the temperature range of 280–320 K, due to hopping conduction with a constant activation energy (constant range hopping) by defects in Tb0.5Nd0.5CoO3 matrix. At lower temperatures (200 – 275 K) in the initial (undoped) Tb0.5Nd0.5CoO3 samples, the Mott-type hopping conductivity mechanism with a variable range hopping and high values of the characteristic temperature To ∼ 109 K was observed. Simultaneously, at 300 K, we observed hopping conductivity on alternating current according to the law σ(ω) ∼ ω-α(ω), where the exponent α, which determines a hopping probability, depends on the frequency. In [Tb0.5Nd0.5CoO3]1−yCy samples, heavily doped with СMF with y = 0.01, carrier transport in the entire studied temperature range of 2–320 K mainly occurs along highly conductive carbon-based channels, formed inside of Tb0.5Nd0.5CoO3 matrix by СMF. At temperatures below 15–20 K, these samples show hopping behavior of R(T) with a variable range hopping over localized states, described by the Mott–Kirkpatrick law. In the temperature range 20–100 K electrical resistance versus temperature R(T) along carbon-based channels obey the law R(T) ∼ Ln T. In this case, the relative magnetoresistance MR(T, B) is characterized by a negative sign at temperatures below 10 K in magnetic fields less than 1 T. This behavior of the R(T, B) dependences were described on the basis of the theory of quantum corrections to the Drude conductivity for two-dimensional samples under conditions of weak localization, which is consistent with the behavior of layered carbon-based materials known from the literature. At T > 150 K curves R(B) follow to Lorentz-like positive magnetoresistive effect in Tb0.5Nd0.5CoO3 matrix in the whole magnetic field range.

Distinct dominant dielectric relaxation mechanisms in CaCu3Ti4O12 – LaMO3 (M = Mn and Fe) perovskite oxide solid solution

Two synthesized perovskite oxide solid solutions, CaCu3Ti4O12 – LaMnO3 and CaCu3Ti4O12 – LaFeO3, possess a crystalline structure embracing an amalgamation of two distinct phases, namely, hexagonal and orthorhombic phases in CaCu3Ti4O12 – LaMnO3 and cubic and orthorhombic phases in CaCu3Ti4O12 – LaFeO3. Examination of dielectric properties reveals colossal dielectric constant (εr), the peak magnitude of εr at 1 kHz being approximately 6×103 and 2.5×104 for Mn and Fe based compound, respectively. Further, complex impedance investigation (CII) establishes the activation energy (Ea) of grains (0.21 eV and 0.07 eV for Mn and Fe based solid solution, respectively) and grain boundaries (0.19 eV and 0.19 eV for Mn and Fe based solid solution, respectively). The deviation in Ea of grains and grain boundaries, as established through CII, in both, Mn and Fe based samples validates the existence of Maxwell-Wagner (M − W) relaxation. The AC conductivity spectrum for both the samples obeying the Jonscher's universal power law (JUPL): σ(ω,T)=σdc+Aωn. The Ea of bulk samples (0.37 eV and 0.19 eV for Mn and Fe based solid solution, respectively) authenticates predominant M − W relaxation (interfacial polarization) with polaron hopping playing the secondary role in Mn based sample, while both, polaron hopping and M − W relaxation being identical contributors towards dielectric nature of Fe based sample.

Analysis of Phase Diagram of CaO-CoOx-ErOy and Crystal Structure of Perovskite (Ca3−xErx)Co2O6−z Solid Solution

In this work, a series of compounds in the CaO-CoOx-ErOy ternary oxide system were synthesized in air at 885 °C, using a high temperature solid-phase synthesis method. The phase boundary of each solid solution region in the CaO-CoOx-ErOy system was determined by X-ray powder diffraction techniques. The phase diagram of the CaO-CoOx-ErOy system at 885 °C includes three series of ternary oxide solid solutions: (Ca3−xErx)Co4O9−z (0 ≤ x ≤ 0.9), (Ca3−xErx)Co2O6−z (0 ≤ x ≤ 1.25), and (Er1−xCax)CoO3−z (0 ≤ x ≤ 0.33). Four three-phase regions and five solid solution tie-line regions were obtained. The structure of the perovskite solid solution (Ca3−xErx)Co2O6−z has been analyzed by Rietveld refinements. With the increase of Er content, the cell parameters of (Ca3−xErx)Co2O6−z exhibit a decreasing trend in a and b directions and an increasing trend in c direction. A brief comparison of the phase diagrams of the CaO-CoOx-ROy (R = La, Dy, and Er) systems in air at 885 °C is provided.

Ferrimagnetic Ordering and Spin-Glass State in Diluted GdFeO3-Type Perovskites (Lu0.5Mn0.5)(Mn1-xTix)O3 with x = 0.25, 0.50, and 0.75.

ABO3 perovskite materials with small cations at the A site, especially those with ordered cation arrangements, have attracted a great deal of interest because they show unusual physical properties and deviations from the general characteristics of perovskites. In this work, perovskite solid solutions (Lu0.5Mn0.5)(Mn1-xTix)O3 with x = 0.25, 0.50, and 0.75 were synthesized by means of a high-pressure, high-temperature method at approximately 6 GPa and approximately 1550 K. All the samples crystallize in the GdFeO3-type perovskite structure (space group Pnma) and have random distributions of the small Lu3+ and Mn2+ cations at the A site and Mn4+/3+/2+ and Ti4+ cations at the B site, as determined by Rietveld analysis of high-quality synchrotron X-ray powder diffraction data. Lattice parameters are a = 5.4431 Å, b = 7.4358 Å, c = 5.1872 Å (for x = 0.25); a = 5.4872 Å, b = 7.4863 Å, c = 5.2027 Å (for x = 0.50); and a = 5.4772 Å, b = 7.6027 Å, c = 5.2340 Å (for x = 0.75). Despite a significant dilution of the A and B sublattices by non-magnetic Ti4+ cations, the x = 0.25 and 0.50 samples show long-range ferrimagnetic order below TC = 89 K and 36 K, respectively. Mn cations at both A and B sublattices are involved in the long-range magnetic order. The x = 0.75 sample shows a spin-glass transition at TSG = 6 K and a large frustration index of approximately 22. A temperature-independent dielectric constant was observed for x = 0.50 (approximately 32 between 5 and 150 K) and for x = 0.75 (approximately 50 between 5 and 250 K).

Does it mix? Insights and attempts to predict the formability of single phase mixed A-cation lead iodide perovskites

Current data suggest that radii and N–H bonds control the solubility and phase segregation in mixed A-cation lead iodide perovskites.

Optical, impedance, and relaxation response of Fe3+ doped double perovskite solid solution

In this report, the effect of Fe3+-incorporation on the crystal structure, vibrational, optical, impedance, modulus, and ferroelectric responses of BaBi1.8Fe0.2TiO6 was discussed. According to XRD and SEM studies, the crystal structure is monoclinic single-phase polycrystalline. The vibrational modes identification from the FTIR spectrum concedes different modes of symmetric and/or antisymmetric vibrations which are usual characteristics of perovskite compounds. The UV-visible study outlines strong absorption and weak reflection near UV and the visible spectrum has a cutoff wavelength of 560 nm. The Tauc and Wood relation estimated the direct band gap energy in the absorbance spectra is 2.70 eV, while the diffused reflectance spectroscopy (DRS) method revealed its value in the reflectance spectra as Eg = 2.84 eV. The resulting bandgap energies suggest that they could be used in photocatalysis. The impedance and modulus analysis supports the semiconducting nature and non-Debye kind relaxation phenomenon in the compound. The PE hysteresis loop with non-zero remanent polarization indicates the material's ferroelectric property, which is suitable for memory storage applications.

Origin of negative electrocaloric effect in Pnma -type antiferroelectric perovskites

Electrocaloric materials of solid state hold great promise for next-generation high-efficiency cooling technology. Besides the normal electrocaloric effect (ECE) in ferroelectrics or relaxors, anomalous ECE with decreasing temperature upon application of an electric field is known to occur in antiferroelectrics (AFEs), and previous understanding refers to the field-induced canting of electric dipoles if there is no phase transition. Here we use a first-principles-based method to study the ECE in Nd-substituted ${\mathrm{BiFeO}}_{3}$ (BNFO) perovskite solid solutions, which has a Pnma-type AFE ground state. We demonstrate another scenario to achieve and explain anomalous ECE, emphasizing that explicit consideration of octahedral tiltings is indispensable for a correct understanding. This mechanism may be general for AFEs for which the antipolar mode is not the primary order parameter or for other commonly occurring Pnma-type perovskites, even without being AFEs. We also find that the negative ECE can reach a large magnitude in BNFO.

Thermochemical Study of CH3NH3Pb(Cl1-xBrx)3 Solid Solutions.

Hybrid organic-inorganic perovskite halides, and, in particular, their mixed halide solid solutions, belong to a broad class of materials which appear promising for a wide range of potential applications in various optoelectronic devices. However, these materials are notorious for their stability issues, including their sensitivity to atmospheric oxygen and moisture as well as phase separation under illumination. The thermodynamic properties, such as enthalpy, entropy, and Gibbs free energy of mixing, of perovskite halide solid solutions are strongly required to shed some light on their stability. Herein, we report the results of an experimental thermochemical study of the CH3NH3Pb(Cl1-xBrx)3 mixed halides by solution calorimetry. Combining these results with molecular dynamics simulation revealed the complex and irregular shape of the compositional dependence of the mixing enthalpy to be the result of a complex interplay between the local lattice strain, hydrogen bonds, and energetics of these solid solutions.

Narrow bandgap ferroelectric [KNbO3](1-x)-[BaCo1/2Nb1/2O3-δ]x solid solution for bulk photovoltaic cell

We report a stable bulk photovoltaic effect in [KNbO3]0.9-[BaCo1/2Nb1/2O3–δ]0.1 (KBCNO-91) solid solution as a result of the light-induced electric field in the orthorhombic phase of KBCNO. Introducing Ba2+ and Co3+ ions in the host lattice of perovskite solid solution, the bandgap can be tuned from 3.2 to 1.59 eV. A photovoltaic cell consists of a 43 nm thin KBCNO-91 perovskite oxide semiconductor sandwiched between the metal electrodes evoke open-circuit voltage (VOC) of >1.9 V, above the bandgap with short-circuit current of ∼1 nA at no external bias (0 V). The fabrication of a two-dimensional ferroelectric solid solution semiconductor with a narrow bandgap of ∼1.59 eV enables the conversion of visible photons into electrical energy in a compact electrode configuration. The device retains its stability for over one year and is expected to be a potential candidate for the next generation of photovoltaic cells.