First-Principles Calculations on Novel Rb-Based Halide Double Perovskites Alloys for Spintronics and Optoelectronic Applications

The outcomes of computational study of electronic, magnetic and optical spectra for A2BX6 (A = Rb;B = Tc, Pb, Pt, Sn, W, Ir, Ta, Sb, Te, Se, Mo, Mn, Ti, Zr and X = Cl, Br) materials have been proceeded utilizing Vanderbilt Ultra Soft Pseudo Potential (US-PP) process. The Rb2PbBr6 and Rb2PbCl6 are found to be a (Г-Г) semiconductors with energy gaps of 0.275 and 1.142 eV, respectively making them promising photovoltaic materials. The metallic behavior of the materials for Rb2BX6 (B = Tc, W, Ir, Ta, Mn, Sb, Mo) has been confirmed showing the attendance of conducting lineaments. The dielectric function is found to be large close to the ultraviolet districts (3.10 - 4.13 eV). The extinction coefficient of the Rb2BX6 has the ability to be used for implements. The band structures and density of states ensure the magnetic semiconductors’ nature of the Rb2Mn (Cl, Br)6 perovskites. The total calculated magnetic moment of Rb2MnCl6 and Rb2MnB6 is 3.00μβ. Advanced spintronic technology requires room-temperature ferromagnetism. The present work confirms that, bromine and chlorine-founded double perovskites are extremely attractive for photovoltaic and optoelectronic devices.

Phase-stable wide-bandgap perovskites enabled by suppressed ion migration

Wide-bandgap(>1.7 eV)perovskites suffer from severe light-induced phase segregation due to high bromine content,causing irreversible damage to devices stability.However,the strategies of suppressing photoinduced phase segregation and related mechanisms have not been fully disclosed.Here,we report a new passivation agent 4-aminotetrahydrothiopyran hydrochloride(4-ATpHCl)with multifunctional groups for the interface treatment of a 1.77-eV wide-bandgap perovskite film.4-ATpH^(+)impeded halogen ion migration by anchoring on the perovskite surface,leading to the inhibition of phase segregation and thus the passivation of defects,which is ascribed to the interaction of 4-ATpH^(+)with perovskite and the formation of low-dimensional perovskites.Finally,the champion device achieved an efficiency of 19.32%with an open-circuit voltage(V_(OC))of 1.314 V and a fill factor of 83.32%.Moreover,4-ATpHCl modified device exhibited significant improved stability as compared with control one.The target device maintained 80%of its initial efficiency after 519 h of maximum power output(MPP)tracking under 1 sun illumination,however,the control device showed a rapid decrease in efficiency after 267 h.Finally,an efficiency of 27.38%of the champion 4-terminal all-perovskite tandem solar cell was achieved by mechanically stacking this wide-bandgap top subcell with a 1.25-eV low-bandgap perovskite bottom subcell.

Thermochemical splitting of CO_(2) on perovskites for CO production: A review

Energy supply dominated by fossil energy has been and remains the main cause of carbon dioxide emissions,the major greenhouse gas leading to the current grave climate change challenges.Many technical pathways have been proposed to address the challenges.Carbon capture and utilization(CCU) represents one of the approaches and thermochemical CO_(2) splitting driven by thermal energy is a subset of the CCU,which converts the captured CO_(2) into CO and makes it possible to achieve closed-loop carbon recirculation.Redox-active catalysts are among the most critical components of the thermochemical splitting cycles and perovskites are regarded as the most promising catalysts.Here we review the latest advancements in thermochemical cycles based on perovskites,covering thermodynamic principles,material modifications,reaction kinetics,oxygen pressure control,circular strategies,and demonstrations to provide a comprehensive overview of the topical area.Thermochemical cycles based on such materials require the consideration of trade-off between cost and efficiency,which is related to actual material used,operation mode,oxygen removal,and heat recovery.Lots of efforts have been made towards improving reaction rates,conversion efficiency and cycling stability,materials related research has been lacking-a key aspect affecting the performance across all above aspects.Double perovskites and composite perovskites arise recently as a potentially promising addition to material candidates.For such materials,more effective oxygen removal would be needed to enhance the overall efficiency,for which thermochemical or electrochemical oxygen pumps could contribute to efficient oxygen removal as well as serve as means for inert gas regeneration.The integration of thermochemical CO_(2) splitting process with downstream fuel production and other processes could reduce costs and increase efficiency of the technology.This represents one of the directions for the future research.

Surface repair of wide-bandgap perovskites for high-performance all-perovskite tandem solar cells

Wide-bandgap(WBG)perovskite solar cells(PSCs)play a fundamental role in perovskite-based tandem solar cells.However,the efficiency of WBG PSCs is limited by significant open-circuit voltage losses,which are primarily caused by surface defects.In this study,we present a novel method for modifying surfaces using the multifunctional S-ethylisothiourea hydrobromide(SEBr),which can passivate both Pb^(-1)and FA^(-1)terminated surfaces,Moreover,the SEBr upshifted the Fermi level at the perovskite interface,thereby promoting carrier collection.This proposed method was effective for both 1.67 and 1.77 eV WBG PSCs,achieving power conversion efficiencies(PCEs)of 22.47%and 19.90%,respectively,with V_(OC)values of 1.28 and 1.33 V,along with improved film and device stability.With this advancement,we were able to fabricate monolithic all-perovskite tandem solar cells with a champion PCE of 27.10%,This research offers valuable insights for passivating the surface trap states of WBG perovskite through rational multifunctional molecular engineering.

Thermal decomposition effect of MgCo_(2)O_(4)nanosheets on ammonium perchlorate-based energetic molecular perovskites

Energetic molecular perovskites have attracted widespread attention in the fields of energy materials due to their high detonation performance.In this work,we reported the effect of MgCo_(2)O_(4) nanosheets on the thermal decomposition of ammonium perchlorate(NH_(4)ClO_(4),AP)-based energetic molecular perovskites(AP-based energetic molecular perovskites).The morphology and structure of the MgCo_(2)O_(4) nanosheets were characterized.And their catalytic effect on the thermal decomposition of AP-based energetic molecular perovskites(H_2pz)[NH_(4)(ClO_(4))_(3)](PAP-4),(H_2dabco)[NH_(4)(ClO_(4))_(3)](DAP-4),(H_2mpz)[NH_(4)(ClO_(4))_(3)](PAP-M_(4)),and (H_2hpz)[NH_(4)(ClO_(4))_(3)](PAP-H_(4)) was analyzed.The results showed that MgCo_(2)O_(4) nanosheets had excellent intrinsically catalytic performance towards enhancing the thermal decomposition of AP-based energetic molecular perovskites.After adding MgCo_(2)O_(4) nanosheets,the thermal decomposition peak temperatures of PAP-4,DAP-4,PAP-M_(4),and PAP-H_(4) had been reduced by35.7℃,48.4℃,37.9℃,and 43.6℃,respectively.And the activation energy(Ea)of the thermal decomposition of AP-based energetic molecular perovskites had been reduced,the Eaof PAP-H_(4) decreased by 46.4 kJ/mol at most among them.The catalytic mechanism of MgCo_(2)O_(4) nanosheets for AP-based energetic molecular perovskites is analyzed.This work provides a reference for the future application of AP-based energetic molecular perovskites.

Influence of Organic Cations on the Crystal and Electronic Structures of Two-dimensional Lead Iodide Perovskites

The crystal structures and electronic structures(including band gap,project density of states,partial charge density,effective mass and electron localization function)of the 2D lead iodide perovskites hybrids with different organic spacer cations of 4-fluorophenylethanaminium(4F-PEA^(+)),ethanolamine(EA^(+)),thienylethylamine(TEA^(+))were investigated using first-principles calculations.It was found the higher dipole moment,the stronger the hydrogen bonding between the organic amino and iodide in the inorganic layer,and the larger the[PbI_(6)]^(4-)octahedral distortions in these crystal structure.Further quantifying the degree of the distortions using OctaDist software showed that the distortion of adjacent[PbI_(6)]^(4-)octahedra had a decisive effect on the band gap.Specifically,the greater deviation of Pb-I-Pb bond angles from 180°,together with the larger distortion of multiple[PbI_(6)]^(4-)octahedron resulted in a wider band gap,which was verified by calculated band gap using different DFT methods.The results outlined the relationships of hydrogen bonding,ocathedra distortion and band structure in 2D perovskites,highlighting the importance of the cations on the structural tuning and optoelectronic properties.

First Principle Study of Cesium-based Lead-free Halide Double Perovskites

Inorganic halide double perovskites A_(2)B'B"X_(6) have gained significant interests for their diverse composition,stable physicochemical properties,and potential for photoelectric applications.The influences of trivalent and monovalent cations on the formation energy,decomposition energy,electronic structure and optical properties of cesium-based lead-free Cs^(+)_(2)B'B"Br_(6) (B'=Na^(+),In^(+)Cu^(+),or Ag^(+);B"=Bi^(3),Sb^(3+),In^(3+)) are systematically studied.In view of the analysis and results of the selected double perovskites,for the double perovskites with different B-site trivalent cation,the band gap increases in the order of Cs_(2)AgInBr_(6),Cs_(2)AgSbBr_(6) and Cs_(2)AgBiBr_(6),with Cs_(2)AgBiBr_(6) possessing the highest thermodynamic stability.Therefore,the Bi-based perovskites are further studied to elucidate the effect of monovalent cation on their stability and electronics.Results show that the thermodynamic stability rises in the sequence of Cs_(2)NaBiBr_(6),Cs_(2)InBiBr_(6),Cs_(2)AgBiBr_(6) and Cs_(2)CuBiBr_(6).Notably,Cs_(2)CuBiBr_(6) exhibits a relatively narrow and appropriate band gap of 1.4634 eV,together with the highest absorption coefficient than other compounds,suggesting that Cs_(2)CuBiBr_(6) is a promising light absorbing material that can be further explored experimentally and be applied to optoelectronic devices.Our research offers theoretical backing for the potential optoelectronic application of cesium-based lead-free halide double perovskites in solar energy conversion.

Infrared optical absorption of Fr?hlich polarons in metal halide perovskites

The formation of Frohlich polarons in metal halide perovskites,arising from the charge carrier-longitudinal optical(LO)phonon coupling,has been proposed to explain their exceptional properties,but the effective identification of polarons in these materials is still a challenging task.Herein,we theoretically present the infrared optical absorption of Frohlich polarons based on the Huang-Rhys model.We find that multiphonon overtones appear as the energy of the incident photons matches the multiple LO phonons,wherein the average phonon number of a polaron can be directly evaluated by the order of the strongest overtone.These multiphonon structures sensitively depend on the scale of electronic distribution in the ground state and the dimensionality of the perovskite materials,revealing the effective modulation of competing processes between polaron formation and carrier cooling.Moreover,the order of the strongest overtone shifts to higher ones with temperature,providing a potential proof that the carrier mobility is affected by LO phonon scattering.The present model not only suggests a direct way to verify Frohlich polarons but also enriches our understanding of the properties of polarons in metal halide perovskites.

Regulation of excitation energy transfer in Sb-alloyed Cs_(4)MnBi_(2)Cl_(12) perovskites for efficient CO_(2) photoreduction to CO and water oxidation toward H_(2)O_(2)

Lead(Pb)-free halide perovskites have recently attracted increasing attention as potential catalysts for CO_(2) photoreduction to CO due to their potential to capture solar energy and drive catalytic reaction.However,issues of the poor charge transfer still remain one of the main obstacles limiting their performance due to the overwhelming radiative and nonradiative charge-carrier recombination losses.Herein,Pb-free Sb-alloyed all-inorganic quadruple perovskite Cs_(4)Mn(Bi_(1-x)Sb_(x))_(2)Cl_(12)(0≤x≤1)is synthesized as efficient photocatalyst.By Sb alloying,the undesired relaxation of photogenerated electrons from conduction band to emission centers of[MnCl6]^(4-)is greatly suppressed,resulting in a weakened PL emission and enhanced charge transfer for photocatalyst.The ensuing Cs_(4)Mn(Bi_(1-x)Sb_(x))_(2)Cl_(12) photocatalyst accomplishes efficient conversion of CO_(2)into CO,accompanied by a surprising production of H_(2)O_(2),a high valueadded product associated with water oxidation.By optimizing Sb^(3+) concentration,a high CO evolution rate of 35.1μmol g^(-1)h^(-1)is achieved,superior to most other Pb and Pb-free halide perovskites.Our findings provide new insights into the mixed-cation alloying strategies for improved photocatalytic performance of Pb-free perovskites and shed light on the rational design of robust band structure toward efficient energy transfer.

Organic-inorganic halide perovskites for memristors

Organic-inorganic halides perovskites(OHPs)have drawn the attention of many researchers owing to their astonishing and unique optoelectronic properties.They have been extensively used for photovoltaic applications,achieving higher than 26%power conversion efficiency to date.These materials have potential to be deployed for many other applications beyond photovoltaics like photodetectors,sensors,light-emitting diodes(LEDs),and resistors.To address the looming challenge of Moore’s law and the Von Neumann bottleneck,many new technologies regarding the computation of architectures and storage of information are being extensively researched.Since the discovery of the memristor as a fourth component of the circuit,many materials are explored for memristive applications.Lately,researchers have advanced the exploration of OHPs for memristive applications.These materials possess promising memristive properties and various kinds of halide perovskites have been used for different applications that are not only limited to data storage but expand towards artificial synapses,and neuromorphic computing.Herein we summarize the recent advancements of OHPs for memristive applications,their unique electronic properties,fabrication of materials,and current progress in this field with some future perspectives and outlooks.

Comparative Performance Analysis of MAPbI3 and FAPbI3 Perovskites: Study of Optoelectronic Properties and Stability

The exploitation of fossil resources to meet humanity’s energy needs is the root cause of the climate warming phenomenon facing the planet. In this context, non-carbon-based energies, such as photovoltaic energy, are identified as crucial solutions. Organic perovskites MAPbI3 and FAPbI3, characterized by their abundance, low cost, and ease of synthesis, are emerging as candidates for study to enhance their competitiveness. It is within this framework that this article presents a comparative analysis of the performances of MAPbI3 and FAPbI3 perovskites in the context of photovoltaic devices. The analysis focuses on the optoelectronic characteristics and stability of these high-potential materials. The optical properties of perovskites are rigorously evaluated, including band gaps, photoluminescence, and light absorption, using UV-Vis spectroscopy and photoluminescence techniques. The crystal structure is characterized by X-ray diffraction, while film morphology is examined through scanning electron microscopy. The results reveal significant variations between the two types of perovskites, directly impacting the performance of resulting solar devices. Simultaneously, the stability of perovskites is subjected to a thorough study, exposing the materials to various environmental conditions, highlighting key determinants of their durability. Films of MAPbI3 and FAPbI3 demonstrate distinct differences in terms of topography, optical performance, and stability. Research has unveiled that planar perovskite solar cells based on FAPbI3 offer higher photoelectric conversion efficiency, surpassing their MAPbI3-based counterparts in terms of performance. These advancements aim to overcome stability constraints and enhance the long-term durability of perovskites, ultimately aiming for practical application of these materials. This comprehensive comparative analysis provides an enlightened understanding of the optoelectronic performance and stability of MAPbI3 and FAPbI3 perovskites, which is critically important to guide future research and development of solar devices that are both more efficient and sustainable.

Propylamine hydrobromide passivated tin-based perovskites to efficient solar cells

The development of tin-based devices with low toxicity is critical for the commercial viability of perovskite solar cells.However because tin halide is a stronger Lewis acid,its crystallization rate is extremely fast,resulting in the formation of numerous defects that affect the device performance of tin-based perovskite solar cells.Herein,propylamine hydrobromide(PABr)was added to the perovskite precursor solution as an additive to passivate defects and fabricate more uniform and dense perovskite films.Because propylamine cations are too large to enter the perovskite lattices,they only exist at the grain boundary to passivate surface defects and promote crystal growth in a preferred orientation.The PABr additive raises the average short-circuit current density from 19.45 to 25.47 mA·cm^(-2)by reducing carrier recombination induced by defects.Furthermore,the device’s long-term illumination stability is improved after optimization,and the hysteresis effect is negligible.The addition of PABr results in a power conversion efficiency of 9.35%.

Beyond two-dimension: One-and zero-dimensional halide perovskites as new-generation passivators for high-performance perovskite solar cells

Perovskite solar cells(PSCs) as a rising star in the photovoltaic field have received rapidly increasing attention recently due to the boosting power conversion efficiencies(PCEs) from 3.8% to 25.7% in the last13 years. Nevertheless, the conventional PSCs with three-dimensional(3D) halide perovskites as light absorbers suffer from inferior PCEs and poor durability under sunlight, high-temperature and humid conditions due to the high defect amount and structural instability of 3D perovskites, respectively. To tackle these crucial issues, lower-dimensional halide perovskites including zero-dimensional(0D), onedimensional(1D), and two-dimensional(2D) perovskites have been employed as efficient passivators to boost the PCEs and durability of 3D-PSCs due to the high structural stability and superior resistance against moisture, heat and sunlight. Therefore, in order to achieve better understanding about the advantages and superiorities of combining low-dimensional perovskites with their 3D counterparts in improving the PCEs and durability of 3D-PSCs, the recent advances in the development and fabrication of mixeddimensional PSCs with 1D/0D perovskites as passivators are summarized and discussed in the review.The superiority of 1D/0D perovskites as passivators over 2D counterparts, the passivation mechanism and the methods of 1D/0D perovskites are also presented and discussed. Furthermore, the rules to choose1D/0D perovskites or relevant spacer cations are also emphasized. On this basis, several specific strategies to design and fabricate mixed-dimensional PSCs with 1D/0D perovskites are presented and discussed.Finally, the crucial challenges and future research directions of mixed-dimensional PSCs with 1D/0D perovskites as passivators are also proposed and discussed. This review will provide some useful insights for the future development of high-efficiency and durable mixed-dimensional PSCs.

Improving the films quality of Sn-based perovskites through additive treatment for high-performance light-emitting diodes

Hybrid lead halide perovskites have received great attention in the field of light-emitting diodes(LEDs)owing to their excellent optoelectronic properties,low cost,and high color purity.To data,the external quantum efficiency(EQE)of lead halide perovskites LEDs has been reported to exceed 20%[1].Even so,the toxicity of conventional lead has cast a gloomy shadow over their further application.

Antimony Potassium Tartrate Stabilizes Wide-Bandgap Perovskites for Inverted 4-T All-Perovskite Tandem Solar Cells with Efficiencies over 26%

Wide-bandgap(WBG)perovskites have been attracting much attention because of their immense potential as a front light-absorber for tandem solar cells.However,WBG perovskite solar cells(PSCs)generally exhibit undesired large open-circuit voltage(VOC)loss due to light-induced phase segregation and severe non-radiative recombination loss.Herein,antimony potassium tartrate(APTA)is added to perovskite precursor as a multifunctional additive that not only coordinates with unbonded lead but also inhibits the migration of halogen in perovskite,which results in suppressed non-radiative recombination,inhibited phase segregation and better band energy alignment.Therefore,a APTA auxiliary WBG PSC with a champion photoelectric conversion efficiency of 20.35%and less hysteresis is presented.They maintain 80%of their initial efficiencies under 100 mW cm^(-2)white light illumination in nitrogen after 1,000 h.Furthermore,by combining a semi-transparent WBG perovskite front cell with a narrow-bandgap tin–lead PSC,a perovskite/perovskite four-terminal tandem solar cell with an efficiency over 26%is achieved.Our work provides a feasible approach for the fabrication of efficient tandem solar cells.

Alternative lead-free mixed-valence double perovskites for high-efficiency photovoltaic applications

Lead-based organic-inorganic hybrid perovskites have exhibited great potential in photovoltaics,achieving power conversion efficiencies(PCEs) exceeding 25%.However,the toxicity of lead and the instability of these materials under moist conditions pose significant barriers to large-scale production.To overcome these limitations,researchers have proposed mixed-valence double perovskites,where Cs_(2)Au~ⅠAu~ⅢI_6 is a particularly effective absorber due to its suitable band gap and high absorptance efficiency.To further extend the scope of these lead-free materials,we varied the trivalent gold ion and halogen anion in Cs_(2)Au~ⅠAu~ⅢI_6,resulting in 18 new structures with unique properties.Further,using first-principles calculations and elimination criteria,we identified four materials with ideal band gaps,small effective carrier mass,and strong anisotropic optical properties.According to theoretical modeling,Cs_(2)AuSbCl_6,Cs_(2)AuInCl_6,and Cs_(2)AuBiCl_6 are potential candidates for solar cell absorbers,with a spectroscopic limited maximum efficiency(SLME) of approximately 30% in a 0.25 μm-thick film.These three compounds have not been previously reported,and therefore,our work provides new insights into potential materials for solar energy conversion.We aim for this theoretical exploration of novel perovskites to guide future experiments and accelerate the development of high-performance photovoltaic devices.

Recent Advances in Synthesis and Properties of Hybrid Halide Perovskites for Photovoltaics

The progress made by the scientific community in emerging photovoltaic technologies over the past two decades has been outstanding. Numerous methods have been developed for the preparation of hybrid organic–inorganic perovskite solar cells. The power conversion efficiency has been up to 14% by a one-step vacuum deposition technique. A serious concern is the toxicity of the materials. In this review, several methods aimed at resolving these problems to some extent have been compiled, including eco-friendly synthesis. Further efficiency enhancements are expected following optimization, and a better fundamental understanding of the internal electron charge transfer, electron–hole diffusion to the corresponding layers, flexibility, and stability-dependent bandgaps is reported. This paper explores the green synthesis of organic–inorganic perovskites for industrialization. Concerning the above facts, a simple low-cost model called‘‘dispersed photovoltaic cells' ' is presented.

Perovskites for Laser and Detector Applications

Perovskite materials have triggered a renewed interest in photovoltaic research in the recent years.They display crystal forms with 0D,1D and 2D,3D motifs,and several chemical forms,namely inorganic(titanates,rubidiates,nobiates,tantalates etc.),organic/inorganic metal halides with single to multiple cations,and even organic polymer or quantum dot-infused hybrids.Each crystal type and chemical form are endowed with specific physicochemical,optical,electronic,and morphological properties.These unique properties render them suitable for targeted applications,namely photovoltaics,LEDs,photocatalysis/electrolysis/solar fuels/solar and Li-ion batteries,gas-sensors,ferroelectrics,capacitors,transistors and memristors,photodetectors,and lasers,for advanced quantum cryptography and outer space applications.At first,the crystal and material types,and physicochemical,morphological,and optoelectronic properties of perovskite materials are discussed.Particularly,we focus on those properties which cumulatively contribute to their application in the abovementioned fields.Simultaneously,a comprehensive discussion about the advances in each field is presented.Structure/property/application relationships with key advances demonstrate the versatility of perovskites in modern optoelectronic technologies.

Progress of Pb-Sn Mixed Perovskites for Photovoltaics: A Review

Pb-Sn mixed perovskites are becoming increasingly popular as narrowbandgap(1.2–1.3 eV)light absorbers in single-junction perovskite solar cells(PSCs)and as bottom cells for all-perovskite tandem solar cells,for highefficiency,low-cost,lightweight,roll-to-roll printable photovoltaic(PV)applications.From the first report of planar Pb:Sn mixed PSCs in 2014,the power conversion efficiencies(PCE)have increased from 10%to 21%by the end of 2020 with an exponential growth in research conducted in this field.Despite much effort,the performance and stability of Pb-Sn mixed PSCs are still limited,which constrains their long-term use in all-perovskite tandem devices.This review highlights the avenues explored in improving different aspects of Pb-Sn mixed PSCs and provides a comprehensive discussion of the interdependent factors affecting the device performance.This includes compositional engineering of the perovskite crystal,absorber layer fabrication and crystallization methods,bandgap tuning,Sn4+reduction,and surface passivation of the absorber layer,as well as the selection of interlayers and electrodes of the final PSC.

High-throughput computational material screening of the cycloalkane-based two-dimensional Dion–Jacobson halide perovskites for optoelectronics

Two-dimensional(2D) layered perovskites have emerged as potential alternates to traditional three-dimensional(3D)analogs to solve the stability issue of perovskite solar cells. In recent years, many efforts have been spent on manipulating the interlayer organic spacing cation to improve the photovoltaic properties of Dion–Jacobson(DJ) perovskites. In this work, a serious of cycloalkane(CA) molecules were selected as the organic spacing cation in 2D DJ perovskites, which can widely manipulate the optoelectronic properties of the DJ perovskites. The underlying relationship between the CA interlayer molecules and the crystal structures, thermodynamic stabilities, and electronic properties of 58 DJ perovskites has been investigated by using automatic high-throughput workflow cooperated with density-functional(DFT) calculations.We found that these CA-based DJ perovskites are all thermodynamic stable. The sizes of the cycloalkane molecules can influence the degree of inorganic framework distortion and further tune the bandgaps with a wide range of 0.9–2.1 eV.These findings indicate the cycloalkane molecules are suitable as spacing cation in 2D DJ perovskites and provide a useful guidance in designing novel 2D DJ perovskites for optoelectronic applications.