Chalcogenide Perovskite Research Articles

Synthesis of the Sn-based CaSnS3 chalcogenide perovskite thin film as a highly stable photoabsorber for optoelectronic applications

We report the synthesis and characterization of the stannous based CaSnS3 chalcogenide perovskite thin film prepared through simple chemical route, and providing a detailed experimental and theoretical investigation of such material. Several attempts were performed to reach optimal conditions, starting from the oxide thin film deposition to the sulfurization process. The crystal identification using X-ray diffraction (XRD) and Raman analysis indicated the formation of a polycrystalline film with no secondary phases detected within the detection limits of the characterization methods employed. Field emission scanning electron microscopy (FE-SEM) screening displayed a notable enhancement on the resulted surfaces, while energy dispersive X-ray spectrometer (EDX) mapping showed the drastic change in the sulfur content with good distribution and homogeneity of the elements on the obtained surfaces. Optical measurements indicated a direct band gap of 1,72 eV in good agreement with our theoretical calculation using the generalized gradient approximation of the modified Becke-Johnson (GGA-mBJ), alongside with an absorption coefficient in the order of 105 cm−1. The Hall effect measurements revealed a p-type conductivity and a carrier concentration of 1.216.1017 cm−3 with an outstanding carrier mobility recorded at 1.314.102 cm2V−1s−1. The photoresponse test was conducted by collecting the Current-Voltage (I-V) variation in dark and under illumination, demonstrating a strong photoabsorption with high stability in ambient atmosphere. The results set the foundations to further investigate the stannous based chalcogenide perovskites as a promising materials for optoelectronic applications.

Ti-Alloying of BaZrS3 Chalcogenide Perovskite for Photovoltaics.

BaZrS3, a prototypical chalcogenide perovskite, has been shown to possess a direct band gap, an exceptionally strong near band edge light absorption, and good carrier transport. Coupled with its great stability, nontoxicity with earth-abundant elements, it is thus a promising candidate for thin film solar cells. However, its reported band gap in the range of 1.7–1.8 eV is larger than the optimal value required to reach the Shockley–Queisser limit of a single-junction solar cell. Here, we report the synthesis of Ba(Zr1–xTix)S3 perovskite compounds with a reduced band gap. It is found that Ti-alloying is extremely effective in band gap reduction of BaZrS3: a mere 4 atom % alloying decreases the band gap from 1.78 to 1.51 eV, resulting in a theoretical maximum power conversion efficiency of 32%. Higher Ti-alloying concentration is found to destabilize the distorted chalcogenide perovskite phase.

Electronic, optical and transport properties of perovskite BaZrS3 compound doped with Se for photovoltaic applications

The chalcogenide perovskite BaZrS3 compound has a huge scientist interest recently due to their properties, and it is known as a new generation of photovoltaic semiconductor, with a specific gap value which is a major element who influences on the efficiency of panels. In this work, the electronic, optical and transport properties of perovskite BaZrS3-xSex compound doped with different concentrations of Se (x = 0%, 10%, 15% and 20%) are investigated using the density functional theory (DFT). It is found that the band gap values decreases by increasing the doping concentrations from 1.59 eV (for 0% of Se) to 1.35 eV (for 20% of Se). In addition, the optical properties indicate that the perovskite BaZrS3 is a good absorber. Also, from the transport proprieties we observed that the BaZrS3-xSex compound is a p-type material. These results show that the BaZrS3 compound doped with Se is a good candidate for photovoltaics applications.

An Environmentally Stable and Lead‐Free Chalcogenide Perovskite

AbstractOrganic–inorganic halide perovskites are intrinsically unstable when exposed to moisture and/or light. Additionally, the presence of lead in many perovskites raises toxicity concerns. Herein, a thin film of barium zirconium sulfide (BaZrS3), a lead‐free chalcogenide perovskite, is reported. Photoluminescence and X‐ray diffraction measurements show that BaZrS3 is far more stable than methylammonium lead iodide (MAPbI3) in moist environments. Moisture‐ and light‐induced degradations in BaZrS3 and MAPbI3 are compared by using simulations and calculations based on density functional theory. The simulations reveal drastically slower degradation in BaZrS3 due to two factors—weak interaction with water and very low rates of ion migration. BaZrS3 photodetecting devices with photoresponsivity of ≈46.5 mA W−1 are also reported. The devices retain ≈60% of their initial photoresponse after 4 weeks under ambient conditions. Similar MAPbI3 devices degrade rapidly and show a ≈95% decrease in photoresponsivity in just 4 days. The findings establish the superior stability of BaZrS3 and strengthen the case for its use in optoelectronics. New possibilities for thermoelectric energy conversion using these materials are also demonstrated.

Design of Lead-Free and Stable Two-Dimensional Dion–Jacobson-Type Chalcogenide Perovskite A′La2B3S10 (A′ = Ba/Sr/Ca; B = Hf/Zr) with Optimal Band Gap, Strong Optical Absorption, and High Efficiency for Photovoltaics

Searching for energetic photovoltaic absorbers is a favorable solution to the current energy crisis. As a star material for solar cells, MAPbI3 (MA = CH3NH3) has a suitable band gap, strong optical...

Ultralow lattice thermal conductivity of chalcogenide perovskite CaZrSe3 contributes to high thermoelectric figure of merit

An emerging chalcogenide perovskite, CaZrSe3, holds promise for energy conversion applications given its notable optical and electrical properties. However, knowledge of its thermal properties is extremely important, e.g. for potential thermoelectric applications, and has not been previously reported in detail. In this work, we examine and explain the lattice thermal transport mechanisms in CaZrSe3 using density functional theory and Boltzmann transport calculations. We find the mean relaxation time to be extremely short corroborating an enhanced phonon–phonon scattering that annihilates phonon modes, and lowers thermal conductivity. In addition, strong anharmonicity in the perovskite crystal represented by the Grüneisen parameter predictions, and low phonon number density for the acoustic modes, results in the lattice thermal conductivity to be limited to 1.17 W m−1 K−1. The average phonon mean free path in the bulk CaZrSe3 sample (N → ∞) is 138.1 nm and nanostructuring CaZrSe3 sample to ~10 nm diminishes the thermal conductivity to 0.23 W m−1 K−1. We also find that p-type doping yields higher predictions of thermoelectric figure of merit than n-type doping, and values of ZT ~0.95–1 are found for hole concentrations in the range 1016–1017 cm−3 and temperature between 600 and 700 K.

Realization of BaZrS3 chalcogenide perovskite thin films for optoelectronics

BaZrS3 is a prototypical chalcogenide perovskite, an emerging class of unconventional semiconductor. Recent results on powder samples reveal that it is a material with a direct band gap of 1.7–1.8 eV, a very strong light-matter interaction, and a high chemical stability. Due to the lack of quality thin films, however, many fundamental properties of chalcogenide perovskites remain unknown, hindering their applications in optoelectronics. Here we report the fabrication of BaZrS3 thin films, by sulfurization of oxide films deposited by pulsed laser deposition. We show that these films are n-type with carrier densities in the range of 1019-1020 cm−3. Depending on the processing temperature, the Hall mobility ranges from 2.1 to 13.7 cm2/Vs. The absorption coefficient is > 105 cm−1 at photon energy >1.97 eV. Temperature dependent conductivity measurements suggest shallow donor levels. By assuring that BaZrS3 is a promising candidate, these results potentially unleash the family of chalcogenide perovskites for optoelectronics such as photodetectors, photovoltaics, and light emitting diodes.

2D Ca3Sn2S7 Chalcogenide Perovskite: A Graphene‐Like Semiconductor with Direct Bandgap 0.5 eV and Ultrahigh Carrier Mobility 6.7 × 104 cm2 V−1 s−1

Graphene, a star 2D material, has attracted much attention because of its unique properties including linear electronic dispersion, massless carriers, and ultrahigh carrier mobility (104 -105 cm2 V-1 s-1 ). However, its zero bandgap greatly impedes its application in the semiconductor industry. Opening the zero bandgap has become an unresolved worldwide problem. Here, a novel and stable 2D Ruddlesden-Popper-type layered chalcogenide perovskite semiconductor Ca3 Sn2 S7 is found based on first-principles GW calculations, which exhibits excellent electronic, optical, and transport properties, as well as soft and isotropic mechanical characteristics. Surprisingly, it has a graphene-like linear electronic dispersion, small carrier effective mass (0.04 m0 ), ultrahigh room-temperature carrier mobility (6.7 × 104 cm2 V-1 s-1 ), Fermi velocity (3 × 105 m s-1 ), and optical absorption coefficient (105 cm-1 ). Particularly, it has a direct quasi-particle bandgap of 0.5 eV, which realizes the dream of opening the graphene bandgap in a new way. These results guarantee its application in infrared optoelectronic and high-speed electronic devices.

Doping and Anisotropy–Dependent Electronic Transport in Chalcogenide Perovskite CaZrSe3 for High Thermoelectric Efficiency

AbstractThe potential of an environmentally friendly and emerging chalcogenide perovskite CaZrSe3 for thermoelectric applications is examined. The orthorhombic phase of CaZrSe3 has an optimum band gap (1.35–1.40 eV) for single‐junction photovoltaic applications. The predictions reveal that CaZrSe3 possesses an absorption coefficient of ≈4 × 105 cm−1 at photon energies of 2.5 eV with an early onset of optical absorption (≈0.2 eV) well below the optimum band gap. Seebeck coefficient, S, is inversely proportional to the carrier mobility as the calculated average effective mass for electrons is higher than for holes; p‐type doping enhances the electrical conductivity, σ. The electronic thermal conductivity κe remains low at all temperatures. The upper limit of the thermoelectric figure of merit (ZTe) attains ≈1.0 when doped at specific chemical potentials, while a high Seebeck coefficient contributes to the ZTe = 1.95 at 50 K for p‐type doping with 1018 cm−3 carrier concentration, demonstrating high thermoelectric efficiency.