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In this study, a novel and efficient method is employed to fabricate tin dioxide films through the thermal decomposition of Sn(OH)4 in a glove box environment. Initially, SnCl2 was dissolved in ethanol at various concentrations and then annealed in glove box, very little Sn(OH)4 was obtained due to the easy decomposition of ethanol at room temperature, and none of the SnO2 was observed. The formation of SnO2 appeared on the films after SnCl2 in ethanol treatment and annealed in air, but this process leads to the decomposition of perovskite. Therefore, a new method need to be proposed so as to prepare SnO2 in glove box. To address this issue, SnCl2 was then dissolved in isopropanol and annealed inside the glove box. The SnO2 films processed with isopropanol as a solvent exhibited better crystallinity, higher purity, improved conductivity, and fewer defects. Furthermore, devices fabricated using SnO2 films prepared with isopropanol also show good efficiency and stability. [ABSTRACT FROM AUTHOR]

Perovskite light‐emitting diodes (PeLEDs) have shown great potential for low‐cost display and lighting technologies, and all‐inorganic blue PeLEDs are recognized as a promising substitute for blue fluorescent/phosphorescent organic light‐emitting diodes (OLEDs) owing to their superior color purity and great stability potential. However, confined by the solution fabrication process, depositing multi‐layered white PeLEDs remains a challenge. Here, a newly designed hybrid perovskite/organic tandem white LED (POTWLED), integrated with a bottom blue PeLED unit and a top orange/(orange + red) OLED unit, to prevent damage to the underlying perovskite layer caused by the deposition of the top emitting layers, is reported. To optimize the performance of POTWLEDs, a conductive passivator of 2,8‐bis(diphenylphosphoryl)dibenzo[b,d] thiophene, with a strong surface binding group of P═O, is introduced to passivate perovskite defects, which promotes a maximum external quantum efficiency (EQE) of 17.3% for blue PeLEDs with an emission peak at 488 nm. As a result, based on the optimized blue PeLED units, a maximum EQE of 23.9% with a low color temperature of 2522 K is obtained for POTWLEDs, which is the highest efficiency for perovskite‐based WLEDs, illustrating the great potential of the hybrid tandem device in fabricating high‐performance perovskite‐based WLEDs. [ABSTRACT FROM AUTHOR]

Fluorescence resonance energy transfer (FRET) based on quantum dots (QDs) and dye molecules have great application potential in biochemical fields. How to achieve an efficient energy transfer process has become an important research topic. Pressure can be used to regulate the energy transfer process, but its regulation on metal halide perovskite systems is rarely reported. Herein, the efficient FRET process between CsPbBr3 QDs and Rhodamine B (RhB) molecules under high pressure is investigated. Upon compression to 1.3 GPa, the FRET rate of the CsPbBr3–RhB composite reaches 0.21 ns−1 and the FRET efficiency is improved from 12.4% to 62.4%, due to enhanced spectral overlap and shortened minimum distance between CsPbBr3 QDs and RhB molecules. This study provides a strategy for achieving efficient FRET research and further promotes the development of applications based on halide perovskite molecular systems. [ABSTRACT FROM AUTHOR]

Monolithic perovskite/organic tandem solar cells (POTSCs) have significant advantages in next‐generation flexible photovoltaics, owing to their capability to overcome the Shockley–Queisser limit and facile device integration. However, the compromised sub‐cells performance challenges the fabrication of high‐efficiency POTSCs. Especially for all‐inorganic wide‐bandgap perovskite front sub‐cells (AIWPSCs) based n‐i‐p structured POTSCs (AIPOTSCs), for which the power conversion efficiency (PCE) is much lower than organic–inorganic mixed‐halide wide‐bandgap perovskite based POTSCs. Herein, an ionic liquid, methylammonium formate (MAFm), based dual‐interface engineering approach is developed to modify the bottom and top interfaces of wide‐bandgap CsPbI2Br films. In particular, the Fm− group of MAFm can effectively passivate the interface defects, and the top interface modification can facilitate the formation of uniform perovskite films with enlarged grain size, thereby mitigating the defects and perovskite grain boundaries induced carrier recombination. As a result, CsPbI2Br‐based AIWPSCs with a high PCE of 17.0% and open‐circuit voltage (VOC) of 1.347 V are achieved. By integrating these dual‐interface engineered CsPbI2Br‐based front sub‐cells with the narrow‐bandgap PM6:CH1007‐based rear sub‐cells, a record PCE of 23.21% is obtained for AIPOTSCs, illustrating the potential of AIPOTSCs for achieving high‐efficiency tandem solar cells. [ABSTRACT FROM AUTHOR]

The vacancy-ordered double perovskite Cs2PdBr6 has the advantages of good optoelectronic properties, environmental friendliness, and high stability. It has been experimentally confirmed by researchers as an optoelectronic material with broad application prospects and research value, and is regarded as a potential substitute for lead halide perovskites. In this paper, based on the first-principles calculations in the framework of density functional theory, the crystal structure, elastic, electronic, and optical properties of Cs2PdBr6 under hydrostatic pressure of 0–6 GPa have been investigated with a step size of 0.5 GPa. The calculated results obtained under the condition of 0 GPa hydrostatic pressure are in good agreement with the existing experimental values. When the hydrostatic pressure is applied, the crystal structure parameters of Cs2PdBr6 appear nonlinear changes, but it can still maintain a stable cubic crystal structure. With the increase of pressure, the bulk modulus, shear modulus, and Young's modulus of Cs2PdBr6 increase gradually, and its ductility also improves gradually. Hydrostatic pressure can reduce the bandgap value of Cs2PdBr6, thereby enhancing the optoelectronic properties such as absorption and conductivity. In summary, hydrostatic pressure can change the bandgap value of Cs2PdBr6, improve its optoelectronic performance, and make it more suitable for use as the light-absorbing layer in solar cells. [ABSTRACT FROM AUTHOR]

Double halide perovskites have outstanding properties for optoelectronic and renewable energy applications. In the present work, we have analszed the structural, mechanical, electronic and optical properties of K2BI6 (B = Ti, Zr and Hf) using the density functional theory. The results show that these perovskites have good mechanical stability. K2HfI6 is a direct bandgap semiconductor with a bandgap of 3.150 eV. K2TiI6 and K2ZrI6 are indirect bandgap semiconductors with bandgaps of 1.828 and 2.515 eV, respectively, but they can be regarded as quasi-direct bandgap semiconductors. They also show good light absorption properties in the ultraviolet–visible wavelength range. These properties make K2BI6 (B = Ti, Zr and Hf) perovskites good candidates for photovoltaic and optoelectronic applications, such as solar cells, photocatalysts and detectors. [ABSTRACT FROM AUTHOR]

All-inorganic perovskite light-emitting diodes (AIPeLEDs) have been demonstrated with superior thermal stability than organic analogues, but the high defect density and lattice strain of all-inorganic perovskites commonly result in compromised efficiency and stability of the devices. Herein, a self-assembled molecule, 4-bromobenzoic acid (BBA), is adopted as an additive to modify CsPbBr 3 -based green AIPeLEDs. In particular, the formic acid group (-COOH) of BBA can interact with the uncoordinated Pb dangling bonds, leading to reduced defects and released lattice strain of perovskites, thereby facilitating the formation of all-inorganic perovskite films with a high photoluminescence quantum yield of 54.5 %. As a result, AIPeLEDs with a high maximum current efficiency of 42.4 cd A−1, and an external quantum efficiency of 11.4 % are obtained. Moreover, promoted by the inhibited non-radiative recombination and released lattice stress, the T 50 lifetime (at an initial brightness of 200 cd m−2) is also improved from 2 h for the control PeLEDs to 8 h for the BBA-treated PeLEDs, which further confirms the superiority of BBA in passivating the AIPeLEDs. • A self-assembled molecule (SAM), 4-bromobenzoic acid (BBA), is adopted as an additive to modify all-inorganic perovskite CsPbBr 3 film crystallization properties for the fabrication of green AIPeLEDs. • The interaction between the formic acid group (-COOH) of BBA with the uncoordinated Pb dangling bonds can lead to reduced defects and released lattice strain of perovskites, which promotes a high photoluminescence quantum yield (PLQY) of 54.5 %. • High-performance AIPeLEDs with an external quantum efficiency (EQE) of 11.4 % and a T 50 lifetime (at an initial brightness of 200 cd m−2) of 8 h are obtained. [ABSTRACT FROM AUTHOR]

In order to better understand and elucidate the structural stability of perovskite materials, the lattice parameters and tolerance factors of three crystal structures of perovskite materials are calculated based on the first principle of density functional theory. We find that the perovskite crystal structures are relatively stable and is consistent with the experimental facts as the tolerance factor 0.81 < T < 1.11. The elastic modulus of three crystal structures of MAPbI3, FAPbI3 and the elastic modulus of FA0.75Cs0.25Sn0.5PB0.5I3 are studied. By Voigt-Reuss-Hill approximation, the elastic properties such as bulk modulus, shear modulus, Young's modulus and Poisson's ratio are obtained. From the elastic modulus Cij, we can find that the other six kinds of crystal structures are relatively stable except for the orthogonal structure of MAPbI3 (c). The ductility and brittle toughness of the material are also discussed by B/G and Poisson's ratio. It is found that MAPbI3 (a) is the hardest and FAPBI3 (a) the weakest. Form the three-dimensional surface view of Young's modulus it is found that their dependence in three-dimensional direction is spherical for an isotropic system. The degree of deviation of the Young's modulus sphere reflects the anisotropy of crystal structures. The degree of elastic anisotropy of organic–inorganic perovskite materials follows the order of FAPbI3(c) > MAPbI3(a) > FA0.75 Cs0.25 Sn0.5Pb0.5I3 > FAPbI3(a) > MAPbI3(b) > MAPbI3(c) >FAPbI3(b). Furthermore, by the adsorption energies and density of states (DOS) of these seven crystals for water molecules, the reasons why perovskite materials are easily denatured in high humidity environment were explored. The results show that perovskite materials are easy to denaturate in high humidity environment. [ABSTRACT FROM AUTHOR]

Double perovskites A 2 CuSbX 6 (A = Cs, Rb, K; X = Cl, Br, I) have been investigated by first principles calculations. According to the tolerance factor, formation energy, binding energy and elastic stability criterion, the other materials except Cs 2 CuSbI 6 can be judged to have mechanical and thermodynamic stability. All the materials are ductile and show potential in wearable devices. The perovskites possess indirect band structures with bandgaps as 1.163 eV, 0.850 eV, 0.305 eV, 1.140 eV and 1.123 eV for Cs 2 CuSbCl 6 , Cs 2 CuSbBr 6 , Cs 2 CuSbI 6 , Rb 2 CuSbCl 6 and K 2 CuSbCl 6 , respectively. Compared with the other two Cl-based perovskites, K 2 CuSbCl 6 exhibits better optoeletronic properties because of its smaller average effective mass(0.294 m 0 for m h ∗ and 0.201 m 0 for m e ∗), longer carrier lifetime and higher light absorption coefficient (6.58 × 104 cm−1) in visible region. In addition, K 2 CuSbCl 6 has a high Debye temperature which represents better stability. The results indicate that K 2 CuSbCl 6 is an excellent candidate for photovoltaic and optoeletronic devices. [ABSTRACT FROM AUTHOR]

The perovskite CH3NH3PbI3 was prepared on a mesoscopic TiO2 film, starting from electrodepositing PbO, to iodination to PbI2, and then interdiffusion reaction with CH3NH3I. The as-prepared film was used as a light absorber for the perovskite solar cells, exhibiting a high PCE of 12.5% under standard AM 1.5 conditions. [ABSTRACT FROM AUTHOR]

We have discussed the materials of solar cell based on hybrid organic–inorganic halide perovskites with formamidinium ( or FA) lead iodide. Firstly, we build the structure of formamidinium lead iodide (FAPbI3) by using the material studio. By using the first-principles calculations, the energy band structure, density of states (DOS), and partial DOS (PDOS) of the hydrazine-iodide lead halide are obtained. Then, we theoretically analyze a design scheme for perovskite solar cell materials, published in [Science354, 861 (2016)], with the photoelectric conversion efficiency that can reach 20.3%. Also, we use non-toxic elements to replace lead in FAPbI3 without affecting its photoelectric conversion efficiency. Here in this work, we explore the energy band structure, lattice constant, light absorption efficiency, etc. After the Ca, Zn, Ge Sr, Sn, and Ta atoms replacing lead (Pb) and through comparing the spectral distributions of the solar spectrum, it can be found that FAGeI3, FASnI3, and FAZnI3 have better absorbance characteristics in the solar spectrum range. If the band gap structure is taken into account, FAGeI3 will become an ideal material to replace FAPbI3, although its performance is slightly lower than that of FAPbI3. The toxicity of Pb is taken into account, and the Ge element can be used as a substitute element for Pb. Furthermore, we explore one of the perovskite materials, i.e., FA0.75Cs0.25Sn0.25Ge0.75I3 whose photovoltaic properties are close to those of FA0.75Cs0.25Sn0.5Pb0.5I3, but the former does not contain toxic atoms. Our results pave the way for further investigating the applications of these materials in relevant technologies. [ABSTRACT FROM AUTHOR]

The vacancy-ordered double perovskite Cs2PdBr6 has the advantages of good optoelectronic properties, environmental friendliness, and high stability. It has been experimentally confirmed by researchers as an optoelectronic material with broad application prospects and research value, and is regarded as a potential substitute for lead halide perovskites. In this paper, based on the first-principles calculations in the framework of density functional theory, the crystal structure, elastic, electronic, and optical properties of Cs2PdBr6 under hydrostatic pressure of 0–6 GPa have been investigated with a step size of 0.5 GPa. The calculated results obtained under the condition of 0 GPa hydrostatic pressure are in good agreement with the existing experimental values. When the hydrostatic pressure is applied, the crystal structure parameters of Cs2PdBr6 appear nonlinear changes, but it can still maintain a stable cubic crystal structure. With the increase of pressure, the bulk modulus, shear modulus, and Young's modulus of Cs2PdBr6 increase gradually, and its ductility also improves gradually. Hydrostatic pressure can reduce the bandgap value of Cs2PdBr6, thereby enhancing the optoelectronic properties such as absorption and conductivity. In summary, hydrostatic pressure can change the bandgap value of Cs2PdBr6, improve its optoelectronic performance, and make it more suitable for use as the light-absorbing layer in solar cells. [ABSTRACT FROM AUTHOR]

The physical properties of Ba 2 ScXO 6 (X = As, Sb) have been studied using first-principles calculations. The research findings indicate that Ba 2 ScXO 6 (X = As, Sb) has negative formation and binding energies, with no imaginary frequencies in the phonon spectrum; satisfying the Born-Huang stability criterion. This implies that Ba 2 ScXO 6 (X = As, Sb) possesses thermodynamic, dynamic, and mechanical stability. Investigation of its mechanical properties reveals that Ba 2 ScXO 6 (X = As, Sb) are an anisotropic brittle material. Studies on the electronic and optical properties found that Ba 2 ScXO 6 (X = As, Sb) are an indirect bandgap insulator with bandgaps of 3.829 eV and 4.796 eV, respectively. It exhibits high absorption intensity for light with wavelengths of around 100–200 nm, and it has the potential to be an excellent optoelectronic device in this range. Furthermore, thermodynamic investigations demonstrate that the material reaches the Dulong-Petit limit at approximately 700 K. Compared to most semiconductor devices, Ba 2 ScXO 6 (X = As, Sb) have a high melting point of 2000 K, indicating good thermal application performance at high temperatures. In conclusion, our research suggests that Ba 2 ScXO 6 (X = As, Sb) may have significant potential as a candidate material for electromechanical and thermoelectric applications. • The double perovskite oxides basic properties of Ba 2 ScXO 6 (X = As, Sb) are predicted via first-principles. • The theoretical calculation shows that the two materials satisfy the mechanical, thermodynamic and dynamic stability. • The results show that they are potential photoelectric materials and provides a theoretical reference for the further study. [ABSTRACT FROM AUTHOR]

The structural, electronic and optical properties of Cs 2 AgSbX 6 (X = I, Br, Cl) were investigated based on first-principles calculation in this paper. The stability of these materials can be determined by the binding energy, formation energy and two tolerance factors. The results indicate that three materials are indirect band gap, with ideal band gap range of materials for photoelectric applications. The bandgap values of Cs 2 AgSbI 6 , Cs 2 AgSbBr 6 and Cs 2 AgSbCl 6 are 0.84 eV, 1.47 eV and 1.87 eV, respectively. Compared with other perovskites, the effective masses of holes of Cs 2 AgSbX 6 are smaller, which is beneficial to the carrier transport and the performance improvement of optoelectronic devices. Moreover, the exploration of optical characteristics reveal the potential utilization of Cs 2 AgSbX 6 in photovoltaic devices. Based on these calculated results, the double-perovskite Cs 2 AgSbX 6 is a potential candidate for photovoltaic applications. [ABSTRACT FROM AUTHOR]

In this paper, the electronic, mechanical and optical properties of Cs 2 InCoX 6 (X = F, Cl, Br) have been studied by first-principle calculation method. The results show that both Cs 2 InCoCl 6 and Cs 2 InCoBr 6 are brittle while Cs 2 InCoF 6 tends to be ductile. Cs 2 InCoF 6 , Cs 2 InCoCl 6 and Cs 2 InCoBr 6 are direct bandgap semiconductors with bandgap values of 3.002eV, 1.129eV and 0.865eV, respectively. Compared with other commonly used perovskite materials, Cs 2 InCoX 6 (X = F, Cl, Br) material has lower effective mass, which is beneficial to improve carrier transport and photoelectric device performance. In addition, Cs 2 InCoF 6 is more suitable as photodetector and photocatalyst, and the absorption curves of Cs 2 InCoCl 6 and Cs 2 InCoBr 6 are well matched with the spectral irradiance of AM1.5. Because Cs 2 InCoCl 6 has a more suitable band gap, it is a potential candidate for absorbing layer materials in solar cells. (a) Cs 2 InCoX 6 (X = F, Cl and Br) is a stable vacancy ordered double halide perovskite direct band gap semiconductor material.(b) The absorption curves of Cs 2 InCoCl 6 and Cs 2 InCoBr 6 match well with the spectral irradiance of AM1.5. [Display omitted] • The Cs 2 InCoX 6 (X = F, Cl, Br) are stable direct bandgap semiconductors with bandgap values of 3.002eV, 1.129eV and 0.865eV, respectively. • The absorption curves of Cs 2 InCoCl 6 and Cs 2 InCoBr 6 have good match with AM1.5 spectral irradiance. • Cs 2 InCoCl 6 is a good candidate material for solar cell absorption layer. [ABSTRACT FROM AUTHOR]

In this paper, the structural, elastic, electronic and optical properties of double-perovskite halides Rb 2 CuBiX 6 are studied using first-principles calculations based on density functional theory. The results show that Rb 2 CuBiX 6 (X = Br, Cl) have thermodynamic and mechanical stability according to the tolerance factor, binding energy, formation energy and Born-Huang stability criterion. The B/G value and Poisson's ratio indicate that Rb 2 CuBiX 6 is a flexible material. Rb 2 CuBiBr 6 and Rb 2 CuBiCl 6 are indirect bandgap semiconductors with bandgap values of 1.11 eV and 1.43 eV, respectively. In addition, the effective masses of electrons of Rb 2 CuBiX 6 are much smaller than that of other perovskite compounds, indicating that they have better carrier mobility. In the visible light range, Rb 2 CuBiX 6 has good dielectric properties and excellent light absorption properties. Therefore, Rb 2 CuBiX 6 has great potential in photovoltaic application due to their suitable bandgap values and excellent optical properties. • The bandgap values of Rb 2 CuBiX 6 (X = Br, Cl) are very suitable for photosensitive materials of solar cells. • The Rb 2 CuBiX 6 can be a potential candidate for excellent light absorbing material. • Rb 2 CuBiX 6 is the structural and thermodynamic stabilities. [ABSTRACT FROM AUTHOR]

Currently, the hybrid perovskite solar cells were exclusively dominated by the Pb or Sn-based perovskite materials, and these materials, however, exhibit long term instabilities associated with ambient hydrolysis and oxidation, limiting their widespread applications. In this work, two layered cupric bromide hybrid perovskite compounds are prepared as light absorbers for application in heterojunction solar cells. The perovskite layers can be deposited from the solutions of the as-prepared perovskites or directly from their precursor solutions at ambient condition. Their preliminary phoyovoltaic performance was carried out in mesoporous TiO 2 heterojunction solar cells. [ABSTRACT FROM AUTHOR]

The structural, elastic, electronic and optical properties of K 2 CuBiX 6 (X ​= ​Br, Cl) are studied by the first principle calculation in this paper. Their structural and thermodynamic stabilities are guaranteed by the formation energy, binding energy and Born-Huang criterion. The results of elastic constants show that the two materials are ductile and can be applied in foldable optoelectronic devices. Besides, The calculated bandgap values are 1.03 ​eV and 1.44 ​eV for K 2 CuBiBr 6 and K 2 CuBiCl 6 , respectively, which is just in the ideal energy gap range of semiconductors. K 2 CuBiX 6 has very small effective mass advantageous to carrier transport. In addition, the optical properties analysis shows that K 2 CuBiX 6 has excellent light absorption properties in ultraviolet–visible wavelength. Due to their suitable bandgaps and good light absorption, K 2 CuBiX 6 has a promising application in solar cells and other optoelectronic devices. In this study, the perovskites K 2 CuBiX 6 (X ​= ​Br, Cl) are proposed as functional materials in solar cells. [Display omitted] • The K 2 CuBiX 6 (X ​= ​Br, Cl) are very suitable for photosensitive materials of solar cells. • The K 2 CuBiX 6 can be a potential candidate for excellent light absorbing material. • The K 2 CuBiX 6 is the structural and thermodynamic stabilities. [ABSTRACT FROM AUTHOR]

Recently, more and more vacancy-ordered double perovskites have been proposed as functional materials in optoelectronic devices. In this paper, a simulation work on the structural, electronic and optical properties of vacancy-ordered double perovskites Tl 2 TiX 6 (X ​= ​Cl, Br, I) has been carried out by using first-principles calculations to reveal their potential application in optoelectronic devices. The Goldschmidt's tolerance factors of these compounds are very close to the ideal value of 1 for cubic perovskites, which confirm their structural stability. Moreover, the formation energies of these compounds were also calculated to evaluate their thermodynamic stability. The theoretically predicted lattice constants of Tl 2 TiCl 6 , Tl 2 TiBr 6 and Tl 2 TiI 6 are 10.060 ​Å, 10.553 ​Å and 11.320 ​Å, respectively, which can provide references for future experimental research. The calculated electronic properties indicate that Tl 2 TiCl 6 , Tl 2 TiBr 6 and Tl 2 TiI 6 have direct bandgaps of 3.39 ​eV, 2.57 ​eV and 1.58 ​eV, respectively, showing ideal bandgap nature for optoelectronic applications. Compared with many vacancy-ordered double perovskites, the three Tl 2 TiX 6 compounds all show the advantage of small effective mass of holes. In addition, the investigation of optical properties, such as reflectivity, absorption coefficient and energy loss function in the photon energy range of 0–25 ​eV further confirms the potential utilization of these Tl 2 TiX 6 compounds in optoelectronic devices. In this study, vacancy-ordered double perovskites Tl 2 TiX 6 (X ​= ​Cl, Br, I) are proposed as functional materials in solar cells and other optoelectronic devices. [Display omitted] • The structural and optoelectronic properties of perovskite materials Tl 2 TiX 6 (X = Cl, Br, I) were studied theoretically. • The results show that they are functional materials with direct bandgap nature. • Compared with many vacancy-ordered double perovskites, the effective mass of holes of the studied compounds is very small. • The three Tl 2 TiX 6 compounds are suitable for optoelectronic applications. [ABSTRACT FROM AUTHOR]

In this paper, the structural, elastic, electronic and optical properties of lead-free perovskite derivatives Cs 2 SeX 6 (X = Cl, Br, I) were studied based on first-principles. The results show that the structures of these perovskite derivatives are stable and they are all anisotropic materials. The three perovskite derivatives Cs 2 SeX 6 (X = Cl, Br, I) are all indirect band gap semiconductors, and the band gap values are 3.28 eV, 2.66 eV and 1.69 eV, respectively. Among the three perovskite derivatives, Cs 2 SeI 6 has not only a suitable band gap, but also a smaller carrier mass, a better absorption spectrum and a larger dielectric function in the visible region. Therefore, the perovskite derivative Cs 2 SeI 6 has the best photoelectric properties. Due to the suitable bandgaps and excellent light absorption, the perovskite derivative Cs 2 SeI 6 can be used as potential photoelectric absorption layer materials of solar cells, while Cs 2 SeCl 6 and Cs 2 SeBr 6 have the potential to develop as other optoelectronic devices. • First-principles method was adopted to study the structural, electronic and optical properties of lead-free perovskite derivatives Cs 2 SeX 6 (X = Cl, Br, I). • Because of the suitable value of bandgap and excellent light absorption, the perovskite Cs 2 SeI 6 can be used as potential photoelectric absorption layer materials of solar cells. • The structures of three perovskites Cs 2 SeX 6 (X = Cl, Br, I) are all stable. [ABSTRACT FROM AUTHOR]