qingde sun - Academia.edu (original) (raw)

Papers by qingde sun

Research paper thumbnail of Data-driven strategy for bandgap database construction of perovskites and the potential segregation study

Journal of materials informatics, May 28, 2024

Data-driven strategy for bandgap database construction of perovskites and the potential segregati... more Data-driven strategy for bandgap database construction of perovskites and the potential segregation study.

Research paper thumbnail of Theoretical exploration of band gap error dependency on band gap size in density functional theory Calculations: CdTe and GeTe as representative cases of two band structure semiconductor types

Computational materials science, Apr 1, 2024

Research paper thumbnail of A simple descriptor for magnetic classification of 2D MXene materials

AIP Advances

Classification of the magnetic state is an essential step to investigate two-dimensional magnetic... more Classification of the magnetic state is an essential step to investigate two-dimensional magnetic materials. Combining high-throughput calculations and machine-learning methods, we have classified the magnetic states of 23 825 MXenes in the aNANt database. A simple descriptor, obtained by averaging the product of the element feature, connectivity, and Coulomb matrix, was found to improve the performance of the machine-learning models. Using this descriptor on 4153 data produced using first-principles calculations, predictive machine-learning models were developed and 1432 MXene with a high saturation magnetization were predicted. The proposed descriptor is useful for the magnetic classification of other materials, and the identified magnetic MXene materials can be used as an important reference for further study.

Research paper thumbnail of Critical Review of Cu‐Based Hole Transport Materials for Perovskite Solar Cells: From Theoretical Insights to Experimental Validation

Advanced materials, May 20, 2024

Research paper thumbnail of Hydrogenated Cs2AgBiBr6 for significantly improved efficiency of lead-free inorganic double perovskite solar cell

Nature Communications, Jun 13, 2022

Development of lead-free inorganic perovskite material, such as Cs 2 AgBiBr 6 , is of great impor... more Development of lead-free inorganic perovskite material, such as Cs 2 AgBiBr 6 , is of great importance to solve the toxicity and stability issues of traditional lead halide perovskite solar cells. However, due to a wide bandgap of Cs 2 AgBiBr 6 film, its light absorption ability is largely limited and the photoelectronic conversion efficiency is normally lower than 4.23%. In this text, by using a hydrogenation method, the bandgap of Cs 2 AgBiBr 6 films could be tunable from 2.18 eV to 1.64 eV. At the same time, the highest photoelectric conversion efficiency of hydrogenated Cs 2 AgBiBr 6 perovskite solar cell has been improved up to 6.37% with good environmental stability. Further investigations confirmed that the interstitial doping of atomic hydrogen in Cs 2 AgBiBr 6 lattice could not only adjust its valence and conduction band energy levels, but also optimize the carrier mobility and carrier lifetime. All these works provide an insightful strategy to fabricate high performance lead-free inorganic perovskite solar cells.

Research paper thumbnail of Bandgap Engineering of Stable Lead‐Free Oxide Double Perovskites for Photovoltaics

Advanced Materials, Mar 6, 2018

Research paper thumbnail of Elucidating the Role of Chalcogenide‐Based Interface Passivators in Enhancing the Stability of Perovskite Solar Cells

Advanced Functional Materials

Chalcogenide‐based Lewis bases are widely used in perovskite solar cells (PSCs) due to their effe... more Chalcogenide‐based Lewis bases are widely used in perovskite solar cells (PSCs) due to their effectiveness in passivating Pb2+ and Pb0‐related defects. However, the underlying principles governing their defect passivation and the relative efficacy of different chalcogen elements remain poorly understood. This study evaluates the effectiveness of oxygen, sulfur, and selenium‐based interface passivator molecules in enhancing the stability and power conversion efficiency (PCE) of perovskite solar cell devices. The hard and soft acid and base (HSAB) principle has been utilized here to gain insights into the defect passivation behavior of chalcogenide‐based molecules. The photoluminescence, ideality factor, and trap density measurements reveal that the sulfide and selenide‐passivated devices exhibit superior defect passivation compared to the oxide‐passivated control device. In terms of stability, the average T75 lifetime (time at which 75% of the initial PCE is retained) of the oxide, s...

Research paper thumbnail of Direct Observation of GroupV Dopant Substitutional Defects in CdTe Single Crystals

Research paper thumbnail of Thermodynamic Stability Landscape of Halide Double Perovskites via High‐Throughput Computing and Machine Learning

Advanced Functional Materials, 2019

Formability and stability issues are of core importance and difficulty in current research and ap... more Formability and stability issues are of core importance and difficulty in current research and applications of perovskites. Nevertheless, over the past century, determination of the formability and stability of perovskites has relied on semiempirical models derived from physics intuition, such as the commonly used Goldschmidt tolerance factor, t. Here, through high‐throughput density functional theory (DFT) calculations, a database containing the decomposition energies, considered to be closely related to the thermodynamic stability of 354 halide perovskite candidates, is established. To map the underlying relationship between the structure and chemistry features and the decomposition energies, a well‐functioned machine learning (ML) model is trained over this theory‐based database and further validated by experimental observations of perovskite formability (F1 score, 95.9%) of 246 A2B(I)B(III)X6 compounds that are not present in the training database; the model performs a lot bette...

Research paper thumbnail of Oxide perovskites, double perovskites and derivatives for electrocatalysis, photocatalysis, and photovoltaics

Energy & Environmental Science, 2019

Oxide perovskites and their derivatives are attractive candidates for the diverse applications in... more Oxide perovskites and their derivatives are attractive candidates for the diverse applications in renewable energy conversions due to their unique structural and compositional flexibility and high material stability.

Research paper thumbnail of Simple descriptor derived from symbolic regression accelerating the discovery of new perovskite catalysts

Nature Communications, Jul 14, 2020

Symbolic regression (SR) is an approach of interpretable machine learning for building mathematic... more Symbolic regression (SR) is an approach of interpretable machine learning for building mathematical formulas that best fit certain datasets. In this work, SR is used to guide the design of new oxide perovskite catalysts with improved oxygen evolution reaction (OER) activities. A simple descriptor, μ/t, where μ and t are the octahedral and tolerance factors, respectively, is identified, which accelerates the discovery of a series of new oxide perovskite catalysts with improved OER activity. We successfully synthesise five new oxide perovskites and characterise their OER activities. Remarkably, four of them, Cs 0.4 La 0.6 Mn 0.25 Co 0.75 O 3 , Cs 0.3 La 0.7 NiO 3 , SrNi 0.75 Co 0.25 O 3 , and Sr 0.25 Ba 0.75 NiO 3 , are among the oxide perovskite catalysts with the highest intrinsic activities. Our results demonstrate the potential of SR for accelerating the data-driven design and discovery of new materials with improved properties.

Research paper thumbnail of Inverse design of stable spinel compounds with high optical absorption <i>via</i> materials genome engineering

Journal of materials chemistry. A, Materials for energy and sustainability, 2022

Materials genome engineering and first principle calculations are used to systematically investig... more Materials genome engineering and first principle calculations are used to systematically investigate the optical properties of AB2X4 (X = O, S and Se) spinel compounds and to provide insight into the design of stable candidates with high absorption coefficients.

Research paper thumbnail of Disparity of the Nature of the Band Gap between Halide and Chalcogenide Single Perovskites for Solar Cell Absorbers

Journal of Physical Chemistry Letters, Jul 25, 2019

have been considered as promising candidates to overcome the stability and toxic issues of halide... more have been considered as promising candidates to overcome the stability and toxic issues of halide perovskites. In this work, we unveiled the disparity of bandgap nature between halide and chalcogenide perovskites. First-principles calculations show that the prototype cubic phase of chalcogenide perovskites exhibit indirect bandgaps with valence band maximum and conduction band minimum located at R and Γ points respectively in Brillion zone. Therefore, the optical transitions near band edges of chalcogenide perovskites differ from its halide counterparts, although its stable orthorhombic phase embodies a direct bandgap. We have further found that the direct-indirect bandgap difference of chalcogenide perovskites in cubic phase demonstrates a linear correlation with t+µ, where t and μ are the tolerance and octahedral factor, respectively, therefore, providing a viable way to search chalcogenide perovskites with a quasi-direct bandgap.

Research paper thumbnail of Thermodynamic Stability Trend of Cubic Perovskites

Journal of the American Chemical Society, Oct 11, 2017

The Supporting Information is available free of charge on the ACS Publications website at DOI: ... more The Supporting Information is available free of charge on the ACS Publications website at DOI:  Computational methodologies, the ΔHD dependence on tolerance factor t, octahedral factor μ and atomic packing ratio η, the linear correlation between ΔHD and (μ + t) η under Shannon' crystal radii, Pauling's covalent radii and various coordination environments,

Research paper thumbnail of Oxide perovskites, double perovskites and derivatives for electrocatalysis, photocatalysis, and photovoltaics

Energy and Environmental Science, 2019

Broader Context Clean energy conversion is crucial to sustain the rapid development of human soci... more Broader Context Clean energy conversion is crucial to sustain the rapid development of human society and mitigate the greenhouse effect and environmental pollution from fossil fuel. Practical utilization of clean energies requires the energy conversions involving different process such as photovoltaics (PV, from solar energy to electrical energy), electrocatalysis (EC, from electrical energy to chemical energy), photocatalysis (PC, from solar energy to chemical energy). A key issue to realize high-efficiency conversion process is to search stable, low-cost and environment-friendly functional materials. Due to the extreme structural and compositional flexibilities, oxide perovskites and their derivates are attractive candidates for the diverse applications aforementioned. This paper reviews the structural and compositional flexibility oxide perovskites and their derivatives and the progress of their applications in clean energy conversion. It attempts to describe how the properties of oxide perovskites and their derivates are tuned for specific applications.

Research paper thumbnail of Stability Engineering of Halide Perovskite via Machine Learning

arXiv (Cornell University), Mar 15, 2018

Perovskite stability is of the core importance and difficulty in current research and application... more Perovskite stability is of the core importance and difficulty in current research and application of perovskite solar cells. Nevertheless, over the past century, the formability and stability of perovskite still relied on simplified factor based on human knowledge, such as the commonly used tolerance factor t. Combining machine learning (ML) with first-principles density functional calculations, we proposed a strategy to firstly calculate the decomposition energies, considered to be closely related to thermodynamic stability, of 354 kinds halide perovskites, establish the machine learning relationship between decomposition energy and compositional ionic radius and investigate the stabilities of 14,190 halide double perovskites. The ML-predicted results enable us to rediscover a series of stable rare earth metal halide perovskites (up to ~10 3 kinds), indicating the generalization of this model and further provide elemental and concentration suggestion for improving the stability of mixed perovskite. The emergence of new applicable materials can often promote the long-lasting development of a particular field in modern science and technology. As a typical example, recent years have witnessed a surge of research interest in solar cell field 1-4 , which is rooted to the discovery of cuttingedge halide perovskite materials. Perovskites solar cells (22.7%) have become a new front runner in the race of cell efficiency and surpassed CdTe (22.1%) and Cu 2 (In,Ga)Se 2 (22.6%) 5 , major contenders in the thin-film solar cell industry. The main remaining obstacle for the commercialization of perovskite solar cell is the long-term stability. Although great efforts are made in cell architecture and encapsulation, the ultimate way is to improve the intrinsic stability of perovskite materials. Apart from photovoltaics, stable halide perovskites also exhibit their great potential in opt-electric applications, such as wide-spectrum light-emitting-diode 6 and highsensitivity X-ray detector 7. Prototype CH 3 NH 3 PbI 3 is easily decomposed into secondary phases such as CH 3 NH 3 I, PbI 2 and I 2 under moisture, air, temperature and light, leading to fast degradation of cell performance, which is reflected by its almost neutral decomposition energy 8. To address the stability issue, compositional management of perovskite ABX 3 leads to tremendous mixed perovskites with double or multiple elemental mixing 9-19 of (K, Rb, Cs, MA, FA), (Pb, Sn, Cd, Mn) and (I, Br, Cl) on A, B and X sites respectively, demonstrating enhanced stability in comparison to their single perovskite counterpart. For example, although the photo-active perovskite phase of RbPbI 3 , CsPbI 3 and FAPbI 3 are unstable at room temperature, proper mixing of (Rb, Cs, FA) on A-site can result in stable mixed-A-site perovskite 15,17. Now, precise control of stability in experiment aims to utilize more mixing elements such as triple-A (Cs,MA,FA)InBiBr 6 20 , triple-A double-X Cs x (MA 0.17 FA 0.83) (1x) Pb(I 0.83 Br 0.17) 3 14 and quadruple-A double-X Rb-FA 0.75 MA 0.15 Cs 0.1 PbI 2 Br 21 , making the problem more complicated. Fundamental insight is urged to understand the effect of elemental mixing and provide guidance for stability engineering i.e. the type of mixing elements and their concentrations. Apart from mixed perovskite, the class of double halide perovskites with a formula W.Y. thank Prof. Xingao Gong for insightful discussion and acknowledge the funding

Research paper thumbnail of Optimization of Doping <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mi>Cd</mml:mi><mml:mi>Te</mml:mi></mml:mrow></mml:math> with Group-V Elements: A First-Principles Study

Physical review applied, May 20, 2021

Group-V substitution at the Te site, X Te (X = P, As, Sb), under Cd-rich conditions is an effecti... more Group-V substitution at the Te site, X Te (X = P, As, Sb), under Cd-rich conditions is an effective way to enhance the hole density and, in the meantime, suppresses the dominant nonradiative carrier recombination center in CdTe, thus, improving the performance of CdTe thin-film solar cells. However, it is not clear which group-V dopant, X, is the most effective dopant, because it is expected that P Te will have the shallowest acceptor level due to its high electronegativity, whereas Sb Te will have the smallest formation energy due to its small size mismatch with Te. Our systematic first-principles study shows that the hole concentration contributed by the acceptor X − Te is limited by the related compensating AX + center that increases simultaneously with X − Te as the chemical potential of dopant X increases. However, the ratio of X − Te acceptors to the AX + donors can be significantly increased if the sample is grown at high temperature and then annealed to room temperature, achieving a high hole density and low Fermi level (E F). We find that all group-V (P, As, and Sb) dopings can achieve maximum hole densities of about 10 17 cm −3 , which are consistent with previous experimental results. Despite the relatively deep acceptor level of 150 meV, Sb doping can achieve a considerable hole density due to the low formation energy of substituting Sb for Te with similar atomic radii. P doping can achieve a higher hole density than that of Sb due to its shallow transition energy at ε(0/−) = 70 meV. However, the highest hole density is achieved through As doping, which is attributed to its balanced defect level at ε(0/−) = 80 meV and relatively small formation energy.

Research paper thumbnail of Thermodynamic Stability Landscape of Halide Double Perovskites via High‐Throughput Computing and Machine Learning

Advanced Functional Materials, Jan 17, 2019

Formability and stability issues are of core importance and difficulty in current research and ap... more Formability and stability issues are of core importance and difficulty in current research and applications of perovskites. Nevertheless, over the past century, determination of the formability and stability of perovskites has relied on semi empirical models derived from physics intuition, such as the commonly used Goldschmidt tolerance factor, t. Here, through high-throughput density functional theory (DFT) calculations, a database containing the decomposition energies, considered to be closely related to the thermodynamic stability of 354 halide perovskite candidates, is established. To map the underlying relationship between the structure and chemistry features and the decomposition energies, a well-functioned machine learning (ML) model is trained over this theory-based database and further validated by experimental observations of perovskite formability (F 1 score, 95.9%) of 246 A 2 B(I)B(III)X 6 compounds that are not present in the training database; the model performs a lot better than empirical descriptors such as tolerance factor t (F 1 score, 77.5%). This work demonstrates that the experimental engineering of stable perovskites by ML could solely rely on training data derived from high-throughput DFT computing, which is much more economical and efficient than experimental attempts at materials synthesis.

Research paper thumbnail of Symbolic Regression Discovery of New Perovskite Catalysts with High Oxygen Evolution Reaction Activity

arXiv (Cornell University), Aug 19, 2019

Symbolic regression (SR) is an emerging method for building analytical formulas to find models th... more Symbolic regression (SR) is an emerging method for building analytical formulas to find models that best fit data sets. Here, SR was used to guide the design of new oxide perovskite catalysts with improved oxygen evolution reaction (OER) activities. An unprecedentedly simple descriptor, μ/t, where μ and t are the octahedral and tolerance factors, respectively, was identified, which accelerated the discovery of a series of new oxide perovskite catalysts with improved OER activity. We successfully synthesized five new oxide perovskites and characterized their OER activities. Remarkably, four of them, Cs0.4La0.6Mn0.25Co0.75O3, Cs0.3La0.7NiO3, SrNi0.75Co0.25O3, and Sr0.25Ba0.75NiO3, outperform the current state-of-the-art oxide perovskite catalyst, Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF). Our results demonstrate the potential of SR for accelerating data-driven design and discovery of new materials with improved properties.

Research paper thumbnail of Hydrogenated Cs2AgBiBr6 for High-Efficient Lead-Free Inorganic Double Perovskite Solar Cell

Research Square (Research Square), Jun 15, 2021

Development of the stable, lead-free inorganic perovskite material is of greatly importance on fa... more Development of the stable, lead-free inorganic perovskite material is of greatly importance on fabricating the third-generation solar cell. Until now, double perovskite, such as Cs2AgBiBr6, has been proved to be one of the most potential candidates to solve the toxicity and stability issues of traditional lead halide perovskite solar cells (PSCs). However, due to a wide and indirect bandgap of Cs2AgBiBr6 film, its light absorption ability is largely limited and the photoelectronic conversion efficiency (PCE) is normally lower than 2.5%. In this text, by using a hydrogenation method, the bandgap (Eg) of Cs2AgBiBr6 films could be tunable from 2.14 eV to 1.61 eV. At the same time, the highest PCE of hydrogenated Cs2AgBiBr6 perovskite solar cell has been improved more than 150% up to 6.27%. To the 2 best of our knowledge, this is a record high efficiency of Cs2AgBiBr6-based perovskite solar cell. Further investigations confirmed that the interstitial doping of atomic hydrogen (H *) in Cs2AgBiBr6 lattice could not only adjust its valence and conduction band energy levels, but also optimize the carrier mobility from 1.71 cm 2 V-1 s-1 to 9.28 cm 2 V-1 s-1 and enhance the carrier lifetime from 18.85 ns to 41.86 ns. All these works provide a new strategy to fabricate the high performance lead-free inorganic PSCs.

Research paper thumbnail of Data-driven strategy for bandgap database construction of perovskites and the potential segregation study

Journal of materials informatics, May 28, 2024

Data-driven strategy for bandgap database construction of perovskites and the potential segregati... more Data-driven strategy for bandgap database construction of perovskites and the potential segregation study.

Research paper thumbnail of Theoretical exploration of band gap error dependency on band gap size in density functional theory Calculations: CdTe and GeTe as representative cases of two band structure semiconductor types

Computational materials science, Apr 1, 2024

Research paper thumbnail of A simple descriptor for magnetic classification of 2D MXene materials

AIP Advances

Classification of the magnetic state is an essential step to investigate two-dimensional magnetic... more Classification of the magnetic state is an essential step to investigate two-dimensional magnetic materials. Combining high-throughput calculations and machine-learning methods, we have classified the magnetic states of 23 825 MXenes in the aNANt database. A simple descriptor, obtained by averaging the product of the element feature, connectivity, and Coulomb matrix, was found to improve the performance of the machine-learning models. Using this descriptor on 4153 data produced using first-principles calculations, predictive machine-learning models were developed and 1432 MXene with a high saturation magnetization were predicted. The proposed descriptor is useful for the magnetic classification of other materials, and the identified magnetic MXene materials can be used as an important reference for further study.

Research paper thumbnail of Critical Review of Cu‐Based Hole Transport Materials for Perovskite Solar Cells: From Theoretical Insights to Experimental Validation

Advanced materials, May 20, 2024

Research paper thumbnail of Hydrogenated Cs2AgBiBr6 for significantly improved efficiency of lead-free inorganic double perovskite solar cell

Nature Communications, Jun 13, 2022

Development of lead-free inorganic perovskite material, such as Cs 2 AgBiBr 6 , is of great impor... more Development of lead-free inorganic perovskite material, such as Cs 2 AgBiBr 6 , is of great importance to solve the toxicity and stability issues of traditional lead halide perovskite solar cells. However, due to a wide bandgap of Cs 2 AgBiBr 6 film, its light absorption ability is largely limited and the photoelectronic conversion efficiency is normally lower than 4.23%. In this text, by using a hydrogenation method, the bandgap of Cs 2 AgBiBr 6 films could be tunable from 2.18 eV to 1.64 eV. At the same time, the highest photoelectric conversion efficiency of hydrogenated Cs 2 AgBiBr 6 perovskite solar cell has been improved up to 6.37% with good environmental stability. Further investigations confirmed that the interstitial doping of atomic hydrogen in Cs 2 AgBiBr 6 lattice could not only adjust its valence and conduction band energy levels, but also optimize the carrier mobility and carrier lifetime. All these works provide an insightful strategy to fabricate high performance lead-free inorganic perovskite solar cells.

Research paper thumbnail of Bandgap Engineering of Stable Lead‐Free Oxide Double Perovskites for Photovoltaics

Advanced Materials, Mar 6, 2018

Research paper thumbnail of Elucidating the Role of Chalcogenide‐Based Interface Passivators in Enhancing the Stability of Perovskite Solar Cells

Advanced Functional Materials

Chalcogenide‐based Lewis bases are widely used in perovskite solar cells (PSCs) due to their effe... more Chalcogenide‐based Lewis bases are widely used in perovskite solar cells (PSCs) due to their effectiveness in passivating Pb2+ and Pb0‐related defects. However, the underlying principles governing their defect passivation and the relative efficacy of different chalcogen elements remain poorly understood. This study evaluates the effectiveness of oxygen, sulfur, and selenium‐based interface passivator molecules in enhancing the stability and power conversion efficiency (PCE) of perovskite solar cell devices. The hard and soft acid and base (HSAB) principle has been utilized here to gain insights into the defect passivation behavior of chalcogenide‐based molecules. The photoluminescence, ideality factor, and trap density measurements reveal that the sulfide and selenide‐passivated devices exhibit superior defect passivation compared to the oxide‐passivated control device. In terms of stability, the average T75 lifetime (time at which 75% of the initial PCE is retained) of the oxide, s...

Research paper thumbnail of Direct Observation of GroupV Dopant Substitutional Defects in CdTe Single Crystals

Research paper thumbnail of Thermodynamic Stability Landscape of Halide Double Perovskites via High‐Throughput Computing and Machine Learning

Advanced Functional Materials, 2019

Formability and stability issues are of core importance and difficulty in current research and ap... more Formability and stability issues are of core importance and difficulty in current research and applications of perovskites. Nevertheless, over the past century, determination of the formability and stability of perovskites has relied on semiempirical models derived from physics intuition, such as the commonly used Goldschmidt tolerance factor, t. Here, through high‐throughput density functional theory (DFT) calculations, a database containing the decomposition energies, considered to be closely related to the thermodynamic stability of 354 halide perovskite candidates, is established. To map the underlying relationship between the structure and chemistry features and the decomposition energies, a well‐functioned machine learning (ML) model is trained over this theory‐based database and further validated by experimental observations of perovskite formability (F1 score, 95.9%) of 246 A2B(I)B(III)X6 compounds that are not present in the training database; the model performs a lot bette...

Research paper thumbnail of Oxide perovskites, double perovskites and derivatives for electrocatalysis, photocatalysis, and photovoltaics

Energy & Environmental Science, 2019

Oxide perovskites and their derivatives are attractive candidates for the diverse applications in... more Oxide perovskites and their derivatives are attractive candidates for the diverse applications in renewable energy conversions due to their unique structural and compositional flexibility and high material stability.

Research paper thumbnail of Simple descriptor derived from symbolic regression accelerating the discovery of new perovskite catalysts

Nature Communications, Jul 14, 2020

Symbolic regression (SR) is an approach of interpretable machine learning for building mathematic... more Symbolic regression (SR) is an approach of interpretable machine learning for building mathematical formulas that best fit certain datasets. In this work, SR is used to guide the design of new oxide perovskite catalysts with improved oxygen evolution reaction (OER) activities. A simple descriptor, μ/t, where μ and t are the octahedral and tolerance factors, respectively, is identified, which accelerates the discovery of a series of new oxide perovskite catalysts with improved OER activity. We successfully synthesise five new oxide perovskites and characterise their OER activities. Remarkably, four of them, Cs 0.4 La 0.6 Mn 0.25 Co 0.75 O 3 , Cs 0.3 La 0.7 NiO 3 , SrNi 0.75 Co 0.25 O 3 , and Sr 0.25 Ba 0.75 NiO 3 , are among the oxide perovskite catalysts with the highest intrinsic activities. Our results demonstrate the potential of SR for accelerating the data-driven design and discovery of new materials with improved properties.

Research paper thumbnail of Inverse design of stable spinel compounds with high optical absorption <i>via</i> materials genome engineering

Journal of materials chemistry. A, Materials for energy and sustainability, 2022

Materials genome engineering and first principle calculations are used to systematically investig... more Materials genome engineering and first principle calculations are used to systematically investigate the optical properties of AB2X4 (X = O, S and Se) spinel compounds and to provide insight into the design of stable candidates with high absorption coefficients.

Research paper thumbnail of Disparity of the Nature of the Band Gap between Halide and Chalcogenide Single Perovskites for Solar Cell Absorbers

Journal of Physical Chemistry Letters, Jul 25, 2019

have been considered as promising candidates to overcome the stability and toxic issues of halide... more have been considered as promising candidates to overcome the stability and toxic issues of halide perovskites. In this work, we unveiled the disparity of bandgap nature between halide and chalcogenide perovskites. First-principles calculations show that the prototype cubic phase of chalcogenide perovskites exhibit indirect bandgaps with valence band maximum and conduction band minimum located at R and Γ points respectively in Brillion zone. Therefore, the optical transitions near band edges of chalcogenide perovskites differ from its halide counterparts, although its stable orthorhombic phase embodies a direct bandgap. We have further found that the direct-indirect bandgap difference of chalcogenide perovskites in cubic phase demonstrates a linear correlation with t+µ, where t and μ are the tolerance and octahedral factor, respectively, therefore, providing a viable way to search chalcogenide perovskites with a quasi-direct bandgap.

Research paper thumbnail of Thermodynamic Stability Trend of Cubic Perovskites

Journal of the American Chemical Society, Oct 11, 2017

The Supporting Information is available free of charge on the ACS Publications website at DOI: ... more The Supporting Information is available free of charge on the ACS Publications website at DOI:  Computational methodologies, the ΔHD dependence on tolerance factor t, octahedral factor μ and atomic packing ratio η, the linear correlation between ΔHD and (μ + t) η under Shannon' crystal radii, Pauling's covalent radii and various coordination environments,

Research paper thumbnail of Oxide perovskites, double perovskites and derivatives for electrocatalysis, photocatalysis, and photovoltaics

Energy and Environmental Science, 2019

Broader Context Clean energy conversion is crucial to sustain the rapid development of human soci... more Broader Context Clean energy conversion is crucial to sustain the rapid development of human society and mitigate the greenhouse effect and environmental pollution from fossil fuel. Practical utilization of clean energies requires the energy conversions involving different process such as photovoltaics (PV, from solar energy to electrical energy), electrocatalysis (EC, from electrical energy to chemical energy), photocatalysis (PC, from solar energy to chemical energy). A key issue to realize high-efficiency conversion process is to search stable, low-cost and environment-friendly functional materials. Due to the extreme structural and compositional flexibilities, oxide perovskites and their derivates are attractive candidates for the diverse applications aforementioned. This paper reviews the structural and compositional flexibility oxide perovskites and their derivatives and the progress of their applications in clean energy conversion. It attempts to describe how the properties of oxide perovskites and their derivates are tuned for specific applications.

Research paper thumbnail of Stability Engineering of Halide Perovskite via Machine Learning

arXiv (Cornell University), Mar 15, 2018

Perovskite stability is of the core importance and difficulty in current research and application... more Perovskite stability is of the core importance and difficulty in current research and application of perovskite solar cells. Nevertheless, over the past century, the formability and stability of perovskite still relied on simplified factor based on human knowledge, such as the commonly used tolerance factor t. Combining machine learning (ML) with first-principles density functional calculations, we proposed a strategy to firstly calculate the decomposition energies, considered to be closely related to thermodynamic stability, of 354 kinds halide perovskites, establish the machine learning relationship between decomposition energy and compositional ionic radius and investigate the stabilities of 14,190 halide double perovskites. The ML-predicted results enable us to rediscover a series of stable rare earth metal halide perovskites (up to ~10 3 kinds), indicating the generalization of this model and further provide elemental and concentration suggestion for improving the stability of mixed perovskite. The emergence of new applicable materials can often promote the long-lasting development of a particular field in modern science and technology. As a typical example, recent years have witnessed a surge of research interest in solar cell field 1-4 , which is rooted to the discovery of cuttingedge halide perovskite materials. Perovskites solar cells (22.7%) have become a new front runner in the race of cell efficiency and surpassed CdTe (22.1%) and Cu 2 (In,Ga)Se 2 (22.6%) 5 , major contenders in the thin-film solar cell industry. The main remaining obstacle for the commercialization of perovskite solar cell is the long-term stability. Although great efforts are made in cell architecture and encapsulation, the ultimate way is to improve the intrinsic stability of perovskite materials. Apart from photovoltaics, stable halide perovskites also exhibit their great potential in opt-electric applications, such as wide-spectrum light-emitting-diode 6 and highsensitivity X-ray detector 7. Prototype CH 3 NH 3 PbI 3 is easily decomposed into secondary phases such as CH 3 NH 3 I, PbI 2 and I 2 under moisture, air, temperature and light, leading to fast degradation of cell performance, which is reflected by its almost neutral decomposition energy 8. To address the stability issue, compositional management of perovskite ABX 3 leads to tremendous mixed perovskites with double or multiple elemental mixing 9-19 of (K, Rb, Cs, MA, FA), (Pb, Sn, Cd, Mn) and (I, Br, Cl) on A, B and X sites respectively, demonstrating enhanced stability in comparison to their single perovskite counterpart. For example, although the photo-active perovskite phase of RbPbI 3 , CsPbI 3 and FAPbI 3 are unstable at room temperature, proper mixing of (Rb, Cs, FA) on A-site can result in stable mixed-A-site perovskite 15,17. Now, precise control of stability in experiment aims to utilize more mixing elements such as triple-A (Cs,MA,FA)InBiBr 6 20 , triple-A double-X Cs x (MA 0.17 FA 0.83) (1x) Pb(I 0.83 Br 0.17) 3 14 and quadruple-A double-X Rb-FA 0.75 MA 0.15 Cs 0.1 PbI 2 Br 21 , making the problem more complicated. Fundamental insight is urged to understand the effect of elemental mixing and provide guidance for stability engineering i.e. the type of mixing elements and their concentrations. Apart from mixed perovskite, the class of double halide perovskites with a formula W.Y. thank Prof. Xingao Gong for insightful discussion and acknowledge the funding

Research paper thumbnail of Optimization of Doping <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mi>Cd</mml:mi><mml:mi>Te</mml:mi></mml:mrow></mml:math> with Group-V Elements: A First-Principles Study

Physical review applied, May 20, 2021

Group-V substitution at the Te site, X Te (X = P, As, Sb), under Cd-rich conditions is an effecti... more Group-V substitution at the Te site, X Te (X = P, As, Sb), under Cd-rich conditions is an effective way to enhance the hole density and, in the meantime, suppresses the dominant nonradiative carrier recombination center in CdTe, thus, improving the performance of CdTe thin-film solar cells. However, it is not clear which group-V dopant, X, is the most effective dopant, because it is expected that P Te will have the shallowest acceptor level due to its high electronegativity, whereas Sb Te will have the smallest formation energy due to its small size mismatch with Te. Our systematic first-principles study shows that the hole concentration contributed by the acceptor X − Te is limited by the related compensating AX + center that increases simultaneously with X − Te as the chemical potential of dopant X increases. However, the ratio of X − Te acceptors to the AX + donors can be significantly increased if the sample is grown at high temperature and then annealed to room temperature, achieving a high hole density and low Fermi level (E F). We find that all group-V (P, As, and Sb) dopings can achieve maximum hole densities of about 10 17 cm −3 , which are consistent with previous experimental results. Despite the relatively deep acceptor level of 150 meV, Sb doping can achieve a considerable hole density due to the low formation energy of substituting Sb for Te with similar atomic radii. P doping can achieve a higher hole density than that of Sb due to its shallow transition energy at ε(0/−) = 70 meV. However, the highest hole density is achieved through As doping, which is attributed to its balanced defect level at ε(0/−) = 80 meV and relatively small formation energy.

Research paper thumbnail of Thermodynamic Stability Landscape of Halide Double Perovskites via High‐Throughput Computing and Machine Learning

Advanced Functional Materials, Jan 17, 2019

Formability and stability issues are of core importance and difficulty in current research and ap... more Formability and stability issues are of core importance and difficulty in current research and applications of perovskites. Nevertheless, over the past century, determination of the formability and stability of perovskites has relied on semi empirical models derived from physics intuition, such as the commonly used Goldschmidt tolerance factor, t. Here, through high-throughput density functional theory (DFT) calculations, a database containing the decomposition energies, considered to be closely related to the thermodynamic stability of 354 halide perovskite candidates, is established. To map the underlying relationship between the structure and chemistry features and the decomposition energies, a well-functioned machine learning (ML) model is trained over this theory-based database and further validated by experimental observations of perovskite formability (F 1 score, 95.9%) of 246 A 2 B(I)B(III)X 6 compounds that are not present in the training database; the model performs a lot better than empirical descriptors such as tolerance factor t (F 1 score, 77.5%). This work demonstrates that the experimental engineering of stable perovskites by ML could solely rely on training data derived from high-throughput DFT computing, which is much more economical and efficient than experimental attempts at materials synthesis.

Research paper thumbnail of Symbolic Regression Discovery of New Perovskite Catalysts with High Oxygen Evolution Reaction Activity

arXiv (Cornell University), Aug 19, 2019

Symbolic regression (SR) is an emerging method for building analytical formulas to find models th... more Symbolic regression (SR) is an emerging method for building analytical formulas to find models that best fit data sets. Here, SR was used to guide the design of new oxide perovskite catalysts with improved oxygen evolution reaction (OER) activities. An unprecedentedly simple descriptor, μ/t, where μ and t are the octahedral and tolerance factors, respectively, was identified, which accelerated the discovery of a series of new oxide perovskite catalysts with improved OER activity. We successfully synthesized five new oxide perovskites and characterized their OER activities. Remarkably, four of them, Cs0.4La0.6Mn0.25Co0.75O3, Cs0.3La0.7NiO3, SrNi0.75Co0.25O3, and Sr0.25Ba0.75NiO3, outperform the current state-of-the-art oxide perovskite catalyst, Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF). Our results demonstrate the potential of SR for accelerating data-driven design and discovery of new materials with improved properties.

Research paper thumbnail of Hydrogenated Cs2AgBiBr6 for High-Efficient Lead-Free Inorganic Double Perovskite Solar Cell

Research Square (Research Square), Jun 15, 2021

Development of the stable, lead-free inorganic perovskite material is of greatly importance on fa... more Development of the stable, lead-free inorganic perovskite material is of greatly importance on fabricating the third-generation solar cell. Until now, double perovskite, such as Cs2AgBiBr6, has been proved to be one of the most potential candidates to solve the toxicity and stability issues of traditional lead halide perovskite solar cells (PSCs). However, due to a wide and indirect bandgap of Cs2AgBiBr6 film, its light absorption ability is largely limited and the photoelectronic conversion efficiency (PCE) is normally lower than 2.5%. In this text, by using a hydrogenation method, the bandgap (Eg) of Cs2AgBiBr6 films could be tunable from 2.14 eV to 1.61 eV. At the same time, the highest PCE of hydrogenated Cs2AgBiBr6 perovskite solar cell has been improved more than 150% up to 6.27%. To the 2 best of our knowledge, this is a record high efficiency of Cs2AgBiBr6-based perovskite solar cell. Further investigations confirmed that the interstitial doping of atomic hydrogen (H *) in Cs2AgBiBr6 lattice could not only adjust its valence and conduction band energy levels, but also optimize the carrier mobility from 1.71 cm 2 V-1 s-1 to 9.28 cm 2 V-1 s-1 and enhance the carrier lifetime from 18.85 ns to 41.86 ns. All these works provide a new strategy to fabricate the high performance lead-free inorganic PSCs.