scholarly journals Strong self-trapping by deformation potential limits photovoltaic performance in bismuth double perovskite

2021 ◽  
Vol 7 (8) ◽  
pp. eabd3160
Author(s):  
Bo Wu ◽  
Weihua Ning ◽  
Qiang Xu ◽  
Manukumara Manjappa ◽  
Minjun Feng ◽  
...  
Keyword(s):  
Density Functional ◽  
Photovoltaic Performance ◽  
Perovskite Solar Cells ◽  
Double Perovskite ◽  
Density Functional Theory Calculations ◽  
Recombination Coefficient ◽  
Potential Candidate ◽  
Deformation Potential ◽  
Electronic Band ◽  
Self Trapping

Bismuth-based double perovskite Cs2AgBiBr6 is regarded as a potential candidate for low-toxicity, high-stability perovskite solar cells. However, its performance is far from satisfactory. Albeit being an indirect bandgap semiconductor, we observe bright emission with large bimolecular recombination coefficient (reaching 4.5 ± 0.1 × 10−11 cm3 s−1) and low charge carrier mobility (around 0.05 cm2 s−1 V−1). Besides intermediate Fröhlich couplings present in both Pb-based perovskites and Cs2AgBiBr6, we uncover evidence of strong deformation potential by acoustic phonons in the latter through transient reflection, time-resolved terahertz measurements, and density functional theory calculations. The Fröhlich and deformation potentials synergistically lead to ultrafast self-trapping of free carriers forming polarons highly localized on a few units of the lattice within a few picoseconds, which also breaks down the electronic band picture, leading to efficient radiative recombination. The strong self-trapping in Cs2AgBiBr6 could impose intrinsic limitations for its application in photovoltaics.

scholarly journals Predicted polymorph manipulation in an exotic double perovskite oxide

2019 ◽  
Vol 7 (39) ◽  
pp. 12306-12311 ◽  
Author(s):  
He-Ping Su ◽  
Shu-Fang Li ◽  
Yifeng Han ◽  
Mei-Xia Wu ◽  
Churen Gui ◽  
...  
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
First Principles ◽  
Density Functional ◽  
Double Perovskite ◽  
Density Functional Theory Calculations ◽  
Perovskite Oxide ◽  
Functional Theory ◽  
First Time ◽  
Perovskite Type

First-principles density functional theory calculations, for the first time, was used to predict the Mg3TeO6-to-perovskite type phase transition in Mn3TeO6 at around 5 GPa.

scholarly journals Intriguing electronic, optical and photocatalytic performance of BSe, M2CO2 monolayers and BSe–M2CO2 (M = Ti, Zr, Hf) van der Waals heterostructures

RSC Advances ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 42-52
Author(s):  
M. Munawar ◽  
M. Idrees ◽  
Iftikhar Ahmad ◽  
H. U. Din ◽  
B. Amin
Keyword(s):  
Density Functional Theory ◽  
Band Structure ◽  
Density Functional ◽  
Photocatalytic Performance ◽  
Electronic Band Structure ◽  
Van Der Waals ◽  
Density Functional Theory Calculations ◽  
Van Der Waals Heterostructures ◽  
Electronic Band ◽  
Functional Theory

Using density functional theory calculations, we have investigated the electronic band structure, optical and photocatalytic response of BSe, M2CO2 (M = Ti, Zr, Hf) monolayers and their corresponding BSe–M2CO2 (M = Ti, Zr, Hf) van der Waals heterostructures.

scholarly journals NIR-Responsive Carbon Nitride of Five-Membered Rings (C3N2) for Photoelectrochemical Biosensing

2020 ◽  
Author(s):  
Hong Yang ◽  
Qing Zhou ◽  
Zhengzou Fang ◽  
Lufang Zhao ◽  
Jin Ma ◽  
...  
Keyword(s):  
Density Functional ◽  
Carbon Nitride ◽  
Density Functional Theory Calculations ◽  
Electronic Band ◽  
Functional Theory ◽  
Hard Materials ◽  
Polymeric Carbon ◽  
First Time ◽  
Electronic Transition Energy

Polymeric carbon nitrides (pCN) have garnered immense attention, ranging from super-hard materials to artificial photosynthesis, due to their exceptional chemical and optoelectronic properties. The most studied C<sub>3</sub>N<sub>4</sub> along with other stoichiometric pCN, such as C<sub>3</sub>N, C<sub>2</sub>N and C<sub>3</sub>N<sub>5</sub>, commonly employed a six-membered ring as the basic units; while the five-membered rings are also popular in a myriad of natural and artificial molecules with a more polarized framework and intriguing functionalities. Here, we report a facile synthesis of C<sub>3</sub>N<sub>2</sub> with a topological structure of five-membered rings, endowing by far the narrowest the first electronic transition energy (0.81 eV) in pCN family. The basic imidazole unit with dangling bonds, resulting in an unusual electronic band of p-π conjugation and split molecular orbitals, was revealed in C<sub>3</sub>N<sub>2</sub> by both experiments and density functional theory calculations. Moreover, a NIR-responsive photoelectrochemical (PEC) biosensor for non-transparent biosamples was constructed for the first time using C<sub>3</sub>N<sub>2</sub> with outstanding performance. This work would not only open a new vista of pCN with different topological structures but also broaden the horizon of their application, such as prospective <i>in vivo</i> PEC bioassay.

scholarly journals NIR-Responsive Carbon Nitride of Five-Membered Rings (C3N2) for Photoelectrochemical Biosensing

2020 ◽  
Author(s):  
Hong Yang ◽  
Qing Zhou ◽  
Zhengzou Fang ◽  
Lufang Zhao ◽  
Jin Ma ◽  
...  
Keyword(s):  
Density Functional ◽  
Carbon Nitride ◽  
Density Functional Theory Calculations ◽  
Electronic Band ◽  
Functional Theory ◽  
Hard Materials ◽  
Polymeric Carbon ◽  
First Time ◽  
Electronic Transition Energy

Polymeric carbon nitrides (pCN) have garnered immense attention, ranging from super-hard materials to artificial photosynthesis, due to their exceptional chemical and optoelectronic properties. The most studied C<sub>3</sub>N<sub>4</sub> along with other stoichiometric pCN, such as C<sub>3</sub>N, C<sub>2</sub>N and C<sub>3</sub>N<sub>5</sub>, commonly employed a six-membered ring as the basic units; while the five-membered rings are also popular in a myriad of natural and artificial molecules with a more polarized framework and intriguing functionalities. Here, we report a facile synthesis of C<sub>3</sub>N<sub>2</sub> with a topological structure of five-membered rings, endowing by far the narrowest the first electronic transition energy (0.81 eV) in pCN family. The basic imidazole unit with dangling bonds, resulting in an unusual electronic band of p-π conjugation and split molecular orbitals, was revealed in C<sub>3</sub>N<sub>2</sub> by both experiments and density functional theory calculations. Moreover, a NIR-responsive photoelectrochemical (PEC) biosensor for non-transparent biosamples was constructed for the first time using C<sub>3</sub>N<sub>2</sub> with outstanding performance. This work would not only open a new vista of pCN with different topological structures but also broaden the horizon of their application, such as prospective <i>in vivo</i> PEC bioassay.

Insights into the Adsorption of Water and Oxygen on the Cubic CsPbBr3 Surfaces: A First-Principle Study

2021 ◽  
Author(s):  
Xin Zhang ◽  
Ruge Quhe ◽  
Ming Lei
Keyword(s):  
Adsorption Energy ◽  
Density Functional ◽  
Degradation Mechanism ◽  
Perovskite Solar Cells ◽  
Density Functional Theory Calculations ◽  
Adsorbed Water ◽  
Energy Difference ◽  
Device Fabrication ◽  
Water Molecules ◽  
Inorganic Perovskite

Abstract The degradation mechanism of the all-inorganic perovskite solar cells in the ambient environment remains unclear. In this paper, water and oxygen molecule adsorptions on the all-inorganic perovskite (CsPbBr3) surface are studied by density-functional theory calculations. In terms of the adsorption energy, the water molecules are more susceptible than the oxygen molecules to be adsorbed on the CsPbBr3 surface. The water molecules can be adsorbed on both the CsBr- and PbBr-terminated surfaces, but the oxygen molecules tend to be selectively adsorbed on the CsBr-terminated surface instead of the PbBr-terminated one due to the significant adsorption energy difference. While the adsorbed water molecules only contribute deep states, the oxygen molecules introduce interfacial states inside the bandgap of the perovskite, which would significantly impact the chemical and transport properties of the perovskite. Therefore, special attention should be paid to reduce the oxygen concentration in the environment during the device fabrication process so as to improve the stability and performance of the CsPbBr3 based devices.

scholarly journals First-principles identification of the charge-shifting mechanism and ferroelectricity in hybrid halide perovskites

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Bumseop Kim ◽  
Jeongwoo Kim ◽  
Noejung Park
Keyword(s):  
Solar Cells ◽  
Photovoltaic Performance ◽  
Perovskite Solar Cells ◽  
High Power Conversion Efficiency ◽  
Electronic Band ◽  
Guiding Principle ◽  
Molecular Cation ◽  
Spatial Charge ◽  
Halide Perovskites ◽  
Halide Perovskite

AbstractHybrid halide perovskite solar cells have recently attracted substantial attention, mainly because of their high power conversion efficiency. Among diverse variants, (CH3NH3)PbI3 and HC(NH2)2PbI3 are particularly promising candidates because their bandgap well matches the energy range of visible light. Here, we demonstrate that the large nonlinear photocurrent in β-(CH3NH3)PbI3 and α-HC(NH2)2PbI3 is mostly determined by the intrinsic electronic band properties near the Fermi level, rooted in the inorganic backbone, whereas the ferroelectric polarization of the hybrid halide perovskite is largely dominated by the ionic contribution of the molecular cation. The spatial charge shift upon excitation is attributed to the charge transfer from iodine to lead atoms in the backbone, which is independent of the presence of the cationic molecules. Our findings can serve as a guiding principle for the design of future materials for halide-perovskite solar cells with further enhanced photovoltaic performance.

scholarly journals Insulator-to-half metal transition and enhancement of structural distortions in $$\text {Lu}_2 \text {NiIrO}_6$$ double perovskite oxide via hole-doping

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Safdar Nazir
Keyword(s):  
Density Functional ◽  
Mixed Valence ◽  
Substantial Reduction ◽  
Double Perovskite ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
Perovskite Oxide ◽  
Hole Doping ◽  
Metallic State ◽  
Spin Moment

AbstractUsing density functional theory calculations, we found that recently high-pressure synthesized double perovskite oxide $$\text {Lu}_2 \text {NiIrO}_6$$ Lu 2 NiIrO 6 exhibits ferrimagnetic (FiM) Mott-insulating state having an energy band gap of 0.20 eV which confirms the experimental observations (Feng et al. in Inorg Chem 58:397–404, 2019). Strong antiferromagnetic superexchange interactions between high-energy half-filled $$\text {Ni}^{+2}$$ Ni + 2 -$$e_g^2\uparrow$$ e g 2 ↑ and low-energy partially filled $$\text {Ir}^{+4}\,t_{2g}^3\uparrow t_{2g}^2\downarrow$$ Ir + 4 t 2 g 3 ↑ t 2 g 2 ↓ orbitals, results in a FiM spin ordering. Besides, the effect of 3d transition metal (TM = Cr, Mn, and Fe) doping with 50% concentration at Ni sites on its electronic and magnetic properties is explored. It is established that smaller size cation-doping at the B site enhances the structural distortion, which further gives strength to the FiM ordering temperature. Interestingly, our results revealed that all TM-doped structures exhibit an electronic transition from Mott-insulating to a half-metallic state with effective integral spin moments. The admixture of Ir 5d orbitals in the spin-majority channel are mainly responsible for conductivity, while the spin minority channel remains an insulator. Surprisingly, a substantial reduction and enhancement of spin moment are found on non-equivalent Ir and oxygen ions, respectively. This leads the Ir ion in a mixed-valence state of $$+4$$ + 4 and $$+5$$ + 5 in all doped systems having configurations of $$5d^5$$ 5 d 5 ($$t_{2g}^3\uparrow t_{2g}^2\downarrow$$ t 2 g 3 ↑ t 2 g 2 ↓ ) and $$5d^4$$ 5 d 4 ($$t_{2g}^2\uparrow t_{2g}^2\downarrow$$ t 2 g 2 ↑ t 2 g 2 ↓ ), respectively. Hence, the present work proposes that doping engineering with suitable impurity elements could be an effective way to tailor the physical properties of the materials for their technological potential utilization in advanced spin devices.

scholarly journals STRUCTURAL, MECHANICAL AND OPTOELECTRONIC STUDY OF DOUBLE PEROVSKITE Cs2SnBr6 USING FIRST PRINCIPLES CALCULATION

2020 ◽  
pp. 6-9
Author(s):  
MD. ABDUR RAZZAQ ◽  
TARIKUL ISLAM
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Perovskite Solar Cells ◽  
Double Perovskite ◽  
Lattice Parameter ◽  
Dielectric Constants ◽  
First Principles Calculation ◽  
Functional Theory ◽  
Direct Band ◽  
Ductile Behavior

The structural, mechanical, electronic and optical properties of double perovskite Cs2SnBr6 have been measured by density functional theory (DFT) calculations. The calculated value of lattice parameter is perfectly tailored with the experimental data. The material shows ductile behavior by Paugh’s ductility index (B/G) at ambient condition. The anisotropic nature of this compound is endorsed by the calculation of Zener anisotropy factor. The direct band gap semiconducting nature with the value of gap is 1.33 eV using PBE potential is also corroborated by electronics properties. Eventually, different optical properties of Cs2SnBr6 such as dielectric constants, refractive index, conductivity, absorption, reflectivity and loss function have been observed and disclose for radiation up to 20 eV. Finally the optical properties corroborate the optoelectronic applications of this compound as all as elite candidate for photovoltaic perovskite solar cells.

scholarly journals Structural Analysis, Phase Stability, Electronic Band Structures, and Electric Transport Types of (Bi2)m(Bi2Te3)n by Density Functional Theory Calculations

2021 ◽  
Vol 11 (23) ◽  
pp. 11341
Author(s):  
Sungjin Park ◽  
Byungki Ryu ◽  
SuDong Park
Keyword(s):  
Density Functional Theory ◽  
Phase Stability ◽  
Thermoelectric Materials ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Electric Transport ◽  
Band Structures ◽  
Electronic Band ◽  
Functional Theory ◽  
Electronic Band Structures

Thermoelectric power generation is a promising candidate for automobile energy harvesting technologies because it is eco-friendly and durable owing to direct power conversion from automobile waste heat. Because Bi−Te systems are well-known thermoelectric materials, research on (Bi2)m(Bi2Te3)n homologous series can aid the development of efficient thermoelectric materials. However, to the best of our knowledge, (Bi2)m(Bi2Te3)n has been studied through experimental synthesis and measurements only. Therefore, we performed density functional theory calculations of nine members of (Bi2)m(Bi2Te3)n to investigate their structure, phase stability, and electronic band structures. From our calculations, although the total energies of all nine phases are slightly higher than their convex hulls, they can be metastable owing to their very small energy differences. The electric transport types of (Bi2)m(Bi2Te3)n do not change regardless of the exchange–correlation functionals, which cause tiny changes in the atomic structures, phase stabilities, and band structures. Additionally, only two phases (Bi8Te9, BiTe) became semimetallic or semiconducting depending on whether spin–orbit interactions were included in our calculations, and the electric transport types of the other phases were unchanged. As a result, it is expected that Bi2Te3, Bi8Te9, and BiTe are candidates for thermoelectric materials for automobile energy harvesting technologies because they are semiconducting.

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