Lead-free Perovskite Materials Research Articles

An inclusive study of lead-free perovskite CsMI3 materials for photovoltaic and optoelectronic appliance explored by a first principles study

The prime objective of this study is to understand the lead-free CsMI3 (M = Pb, Mg, Ga, Ca, Ba, Sr) perovskites for photovoltaic and optoelectronic applications using first-principle calculations. This study considered the structural aspects along with the mechanical, electrical, optical, and thermal properties. The formation energy, phonon dispersion curve, and elastic constants were calculated to check the structural stability of the compounds. The computed Poisson ratios (ν) support the CsMI3 compounds' ductility; only the CsMgI3 compounds lie on the ductile-brittle transition line. However, the compounds' ductility is confirmed by the Cauchy pressure, which also reflects the materials' mechanism of mechanical failure. The band structure calculations confirmed the energy band gap, Eg, in the range of 1.63–3.26 eV, which makes them suitable for absorbing materials in solar cell applications. The optical properties calculations revealed strong photoconductivity, low reflectivity, and high absorption coefficient, all of which show photovoltaic properties given the materials use in the solar cell application. Among the titled compounds, CsMgI3 will be the best replacement of Pb-based perovskites for photovoltaic and optoelectronic appliances. The substitution of I by Br in the CsMgI3 causes a significant improvement (band gap is increased from 1.12 to 1.87 eV; absorption coefficient is also increased) in the photovoltaic properties. The Eg and α further increase due to doping into the CsMg(I1-xBrx)3 where x = (0.25) makes them apposite for solar cell materials. The best combination, CsMg(I0.75Br0.25)3, shows Eg ∼ 1.4 eV, which may be considered as the optimum band gap for the highest efficiency of a single solar cell according to the Shockley-Queisser limit.

A Systematical Study on Bands and Defects of CsBX3 (B = Pb, Sn, Ge, X = Cl, Br, I) Perovskite Based on First Principles.

Metal halide perovskites have attracted considerable attention as novel optoelectronic materials for their excellent optical and electrical properties. Inorganic perovskites (CsPbX3, X = Cl, Br, I) are now viable alternative candidates for third-generation photovoltaic technology because of their high photoelectric conversion efficiency, high carrier mobility, good defect tolerance, simple preparation method and many other advantages. However, the toxicity of lead is problematic for practical implementation. Thus, the fabrication of lead-free perovskite materials and devices has been actively conducted. In this work, the energy band and photoelectric properties of inorganic perovskites CsBX3 (B = Pb, Sn, Ge, X = Cl, Br, I) have been investigated with the first principles calculation, and the possible defect energy levels and their formation energies in different components, in particular, have been systematically studied. The advantages and disadvantages of Sn and Ge as replacement elements for Pb have been demonstrated from the perspective of defects. This study provides an important basis for the study of the properties and applications of lead-free perovskites.

Investigating structural, phonons, optoelectronics, and thermodynamic properties of lead-free double perovskites of A-site cation ordering in LiXTl2Cl6 (X= Sc and Y) compounds for green energy applications

This study explores the structural, phonons, optoelectronic, and thermodynamic properties of LiXTl2Cl6 (X = Sc and Y) compounds. These double perovskite materials are particularly interesting due to their potential for green energy applications. We employ state-of-the-art computational simulation techniques to investigate the structural properties of these compounds, focusing on the cation ordering in the A-site of the perovskite structure. Through density functional theory (DFT) calculations, we determine the equilibrium crystal structure and lattice parameters, shedding light on the stability of these materials. Furthermore, we analyze the phonon spectra to assess the materials' vibrational properties, including the presence of any phonon modes that may impact thermal stability and thermal transport. Optoelectronic properties, such as band gaps and optical absorption spectra, are also explored to evaluate the suitability of these materials for photovoltaic and light-emitting applications. We investigate their electronic structure and consider the potential for efficient charge carrier generation and transport. The thermodynamic properties, such as heat capacity, entropy, and enthalpy, are calculated to provide insight into the compounds' thermal behavior under various environmental conditions, which is crucial for green energy applications, including thermal energy conversion. This comprehensive investigation into the LiXTl2Cl6 (X = Sc and Y) compounds aims to contribute to developing lead-free double perovskite materials with tailored properties for a range of green energy applications, paving the way for more sustainable and environmentally friendly energy solutions.

Synthesis, characterization, and optical studies of lead-free perovskite, Cs3M2Br9 (M = Bi, Sb) nanocrystals

In recent years, there has been a surge in research interest surrounding all inorganic lead perovskite nanocrystals (NCs) owing to their exceptional performance in various optoelectronic devices. Nevertheless, the presence of lead and concerns regarding its toxicity and stability have cast a shadow over their potential wide-ranging applications. In this study, we present the synthesis of two lead-free all-inorganic perovskite materials, Cs3M2Br9 (where M = Bi or Sb), in bulk form, using an aqueous halide acid medium. Additionally, we describe a top-down approach for the fabrication of two lead-free all-inorganic perovskite, Cs3M2Br9 (M = Bi or Sb) NCs. The Cs3Sb2Br9 NCs display a sheet-like morphology, while Cs3Bi2Br9 NCs exhibit a cubic structure. The PL spectra of Cs3Sb2Br9 and Cs3Bi2Br9 NCs exhibit distinct emission peaks at 476 nm and 472 nm, respectively, with relatively narrow full width at half maximum (FWHM) of 44 nm and 38 nm, respectively. Cs3Sb2Br9 and Cs3Bi2Br9 NCs demonstrate excellent thermal stability up to 320 °C and 470 °C, respectively. Notably, the high photoluminescence quantum yield (PLQY) of these NCs, Cs3Sb2Br9 NCs (31 %) and Cs3Bi2Br9 NCs (36 %) are highly beneficial for optoelectronic applications is observed.

First-principles study on the stability and degradation of the lead-free double perovskite materials Cs2B'BiCl6 (B' = Li, Na, K) under natural environment

The stability of perovskite solar cell materials in the natural environment is crucial to their commercial application. Understanding the detailed interaction mechanism between the air or water molecules (H2O) and the perovskite materials is a key way to explore their stabilities. In this study, we evaluate the geometric stabilities and thermodynamic stabilities of the lead-free Cs2B'BiCl6 (B' = Li, Na, K) double perovskite materials, and further explore the effect of air and H2O molecules on the stability and degradation of the Cs2B'BiCl6 double perovskite materials. The calculated results indicate that the pristine Cs2B'BiCl6 materials possess good geometric stabilities and thermodynamic stabilities. Under natural environment, the N2, O2, and CO2 gas molecules hardly penetrate into Cs2LiBiCl6 and Cs2NaBiCl6 because of positive absorption energies, while N2 and O2 can easily penetrate into Cs2KBiCl6 due to negative absorption energies. In contrast, the H2O molecules can easily penetrate into all Cs2B'BiCl6 double perovskite materials with negative absorption energies. Furthermore, the penetration of H2O molecules causes structural deformations of the double perovskites and the resultant rotation or rupture of some octahedra. Further simulations of H2O molecules adsorption on the surface of the double perovskites reveal that the adsorption energies of H2O molecules at all adsorption sites are negative, indicating that the Cs2B'BiCl6 double perovskite materials are prone to absorb H2O molecules in a humid environment. Therefore, the H2O molecules are the main factor affecting the stability and degradation of all Cs2B'BiCl6 double perovskite materials. Additionally, Cs2KBiCl6 shows much worse stability, which is responsible for the scarcely experimental reports on its synthesis and characterization.

Lead-free Cs₂NaInCl₆:Bi³⁺/Mn2⁺ double perovskite nanocrystals to nanosheets with improved photoluminescence quantum yield for anti-counterfeit marks and LED applications

Lead-free double perovskites (DPs) in the form of two-dimensional (2D) nanosheets (NSs) have emerged as exceptional candidates compared to zero-dimensional (0D) nanocrystals (NCs). This preference is attributed to their intriguing fundamental properties and promising applications in optoelectronics. Notably, NSs offer superior performance due to their enhanced surface passivation capabilities, facilitating more efficient treatment of surface defects and thereby enhancing optoelectronic properties. However, the realization of Cs2NaInCl6 as lead-free DPs NSs is yet to be achieved. In this study, we successfully synthesized Cs2NaInCl6 co-doped with Bi3+/Mn2+ NSs. The two-step solution process synthesis enables us to achieve dimensionality control, progressing from 0D NCs to 2D NSs. Comprehensive optical spectroscopy analyses reveal that the NSs exhibit a suppressed non-radiative decay rate (Knr) of 5.03 × 10−3 ns−1 in contrast to NCs with a Knr of 3.21 × 10−2 ns−1. This observation is indicative of a well-passivated surface in NSs. In contrast, NSs with identical composition and surface morphology significantly enhance the photoluminescence quantum yields (PLQYs) up to 73%, which represents the highest PLQYs recorded in Cs2NaInCl6 DPs to the best of our knowledge. Beyond fundamental investigations, the study explores the practical applications of these NSs as anti-counterfeit marks created on a flexible substrate, demonstrating robust emission under UV light. Additionally, the fabrication and testing of a light-emitting diode (LED) showcase the versatility of these NSs in optoelectronic devices. This comprehensive exploration of the optical, morphological, and application aspects of Cs₂NaInCl₆ doped with Bi³⁺/Mn2⁺ NSs contributes valuable insights to the evolving landscape of lead-free perovskite materials, highlighting their potential for diverse technological applications.

Efficient and Stable Multicolor Emissions of the Coumarin-Modified Cs3LnCl6 Lead-Free Perovskite Nanocrystals and LED Application.

Lanthanide-based lead-free perovskite materials hold great promise for the development of high-resolution full-color displays in the future. Here, various Cs3LnCl6 perovskite nanocrystals (NCs) emitting light across the visible to near-infrared spectrum with remarkably high photoluminescence quantum yield (PLQY) are systemically prepared. Especially, by introducing multifunctional coumarin small molecules into Cs3EuCl6 NCs as an intermediate state, Cs3EuCl6 NCs can achieve an impressive PLQY of 92.4% with pure red emission and an exceptional energy transfer efficiency of nearly 93.2%. Furthermore, the lanthanide-based electroluminescent devices in red, green, and blue are successfully fabricated. Among them, the Cs3EuCl6-NC-based red light-emitting diode (LED) demonstrates a FWHM of 18nm at 617nm, an external quantum efficiency up to 5.17%, and a maximum brightness of 2373cd m-2, which is the most excellent reported for lead-free narrowband (within 20nm) emission devices. Notably, these devices exhibit an operating half-life of 440 h at a brightness level of 100cd m-2, surpassing the performance of most reported lead-free perovskite LEDs (PLEDs). This work opens up exciting possibilities for the future commercialization of lanthanide-based PLEDs in the display industry, paving the way for more vibrant, energy-efficient, and long-lasting display technologies.

All oxide lead-free bismuth ferrite perovskite absorber based FTO/ZnO/BiFeO3/Au solar cell with efficiency ∼ 12%: First principle material and macroscopic device simulation studies

We report the photovoltaic response of bismuth ferrite (BiFeO3) multiferroic absorber based all oxide FTO/ZnO/BiFeO3/Au solar cell using density functional theory for materials optoelectronic properties and macroscopic device simulation-based hybrid approach. The structural, electronic, and optical properties of BiFeO3 are investigated using density functional theory (DFT). The band structure and density of states of R3c-BiFeO3 are computed considering the Hubbard parameter Ueff∼4.2eV for both Fe-3d and O-2p orbitals for matching the experimental bandgap of ∼2.5eV. The computed optical properties, such as absorption for rhombohedral R3c-BiFeO3, are used to investigate FTO/ZnO/BiFeO3/Au solar cell performance using a macroscopic device simulation approach. The thickness, acceptor concentration, defect concentration of the absorber layer, interface defect density, electron affinity of the electron transport layer, and the impact of series, shunt resistance, and metal back contact are investigated to optimize the photovoltaic response under realistic conditions. The optimum photoconversion efficiency (PCE) is ∼11.92% with open circuit voltage (Voc) of 1.033V, short circuit current density (Jsc) of 15.27mA/cm2, and fill factor (FF) of 75.59%. This study on BiFeO3-based absorber materials opens a way to realize lead-free perovskite absorber material with a potential for realizing all oxide solar cells.

Near-infrared Cr3+-doped lead-free halide perovskite microcrystals for information encryption and temperature thermometry

Lead-free double perovskite materials have attracted lots of interest because they can be doped with luminescence activators to modify their optical characteristics and improve photoluminescence performances.

Morphological, structural, optical and dielectric analysis of Cs2TiBr6 perovskite nanoparticles.

In the pursuit of lead-free perovskite materials suitable for harnessing solar energy, a recent discovery has emerged regarding Cs2TiBr6. This compound has garnered attention as a prospective candidate, exhibiting favorable optical and electrical characteristics alongside exceptional resilience when subjected to environmental strains. This study details the successful synthesis of non-hazardous metal halide nanoparticles of Cs2TiBr6via the slow cooling method. Comprehensive investigations into the structural, optical, and dielectric characteristics have been undertaken. The temperature sensitivity of various electrical properties, including the dielectric constant, loss factor, electric modulus, and AC/DC conductivity, is evident in this perovskite material. This phenomenon is observed across a frequency range of 1 to 107 Hz. Furthermore, examination of the Nyquist plot highlights the distinctive contributions of both grain and grain boundaries to the overall impedance characteristics. In the high-frequency range, it is observed that the dielectric constant exhibits an upward trend as the temperature rises. Examination of the adapted Cole-Cole plot unveils that both space charge and free charge conductivity escalate with increasing temperature, while concurrently, the relaxation time experiences a reduction with the temperature's ascent. We observed an asymmetrical pattern in the electric modulus spectra at varying temperatures using a modified Kohlrausch-Williams-Watts equation. This asymmetry is consistent with the inherent non-Debye nature of perovskite materials. Additionally, as the temperature increases, we note a shift in the imaginary component of the electric modulus spectra, transitioning from a non-Debye character towards a semi-Debye nature, though it does not achieve a strictly Debye-type response. This transformation indicates the semiconducting properties of the material. We elucidate the AC conductivity behavior in Cs2TiBr6 by employing the non-overlapping small-polaron tunneling (NSPT) mechanism as the basis. The activation energy, as determined from both the modulus spectra and DC conductivity, aligns closely, providing robust evidence for the congruence between the relaxation dynamics and the conduction mechanism. In addition to these attributes, Cs2TiBr6 exhibits a substantial dielectric constant coupled with negligible dielectric loss, thus establishing its potential suitability for energy harvesting devices.

Comparative Study of Lead-free Perovskite Materials MASnI3, MASnBr3 and MAGeI3 to Design, Simulate and Optimize Lead Free PSC

Comparative Study of Lead-free Perovskite Materials MASnI3, MASnBr3 and MAGeI3 to Design, Simulate and Optimize Lead Free PSC

In situ doped Cs2AgIn0.9Bi0.1Cl6:8%Yb,2%Er/PVDF composite films for the printing of multimodal fluorescent anti-counterfeiting marks

The fluorescent anti-counterfeiting technology has become one of the most desirable candidates in practical anti-counterfeiting applications owing to its adjustable emission, high recognition and design flexibility. However, the security level of single emitting fluorescent materials was lower, and no longer able to cope with current forgery techniques, so the development of higher level multimodal fluorescent anti-counterfeiting technologies was urgent. In this report, lead-free double perovskite (DP) material CsAgBiCl6 was chosen as the host and a technique for in situ growth in polymer polyvinylidene difluoride (PVDF) was proposed to obtain large-scale high-quality Cs2AgBiCl6/PVDF composite films (CFs). Subsequently, the Cs2AgIn0.9Bi0.1Cl6:8%Yb,2%Er/PVDF CFs with both down-conversion and up-conversion optical properties was achieved by hybrid (In3+/Yb3+/Er3+) doping, which was able to displayed inconsistent fluorescence emission (orange and green) under different excitation sources, and their fluorescence intensities exhibited tunability with the change of the environmental temperature, greatly enhancing its competitiveness in the field of fluorescent anti-counterfeiting. Finally, different anti-counterfeiting marks have been designed by the screen-printing process, and the complex encryption once again ensured the security of the information, while bringing a new gospel to the subsequent development of lead-free DP materials.

Revealing high temperature structural behavior behind the enhanced piezoelectric properties of lead-free 0.7BiFeO3-0.3BaTiO3 ceramics by in-situ process

Local domain evolution plays a vital role in modulating the high-temperature piezoelectricity of ferroelectric ceramics. Herein, 0.7BiFeO3-0.3BaTiO3-xBi(Zn0.5Ti0.5)O3 (referred to as BF-BT-xBZT, 0.00≤x≤0.05) high temperature lead free piezoelectric ceramics were prepared by a solid-phase method. All ceramics are at the morphotropic phase boundary (MPB), with an overall decreasing trend of the R/Pc phase fraction upon heating. STEM reveals the in-situ heterogeneity of polar nanodomains. Due to the modulation with proper R/PC ratio and a multilayer nanodomain ratio, the in-situ d33 and Tdr values increase from 495 pC/N and 314 °C to 502 pC/N and 360 °C with increasing content of (Zn1/2Ti1/2)3+ from x=0 to x=0.04 while maintaining a high Curie temperature (Tc>470 °C). This study provides a new paradigm for studying the in-situ depolarization behavior of lead-free perovskite materials and to optimizing the high-temperature piezoelectric properties by tuning the domain scale.

Impact of Structural Strain in Perovskite Epitaxial Thin Films on Their Functional Properties

The strain engineering effects induced by different means, e.g., the substrate lattice mismatch and/or chemical doping, on the functional properties of perovskite thin films have triggered interest in the use of these materials in different applications such as energy storage/generation or photonics. The effects of the film’s thickness and strain state of the structure for the lead-free perovskite ferrite-based materials (BiFeO3-BFO; Y-doped BiFeO3-BYFO; LaFeO3-LFO) on their functional properties are highlighted here. As was previously demonstrated, the dielectric properties of BFO epitaxial thin films are strongly affected by the film thickness and by the epitaxial strain induced by the lattice mismatch between substrate and film. Doping the BiFeO3 ferroelectric perovskite with rare-earth elements or inducing a high level of structural deformation into the crystalline structure of LaFeO3 thin films have allowed the tuning of functional properties of these materials, such as dielectric, optical or photocatalytic ones. These changes are presented in relation to the appearance of complex ensembles of nanoscale phase/nanodomains within the epitaxial films due to strain engineering. However, it is a challenge to maintain the same level of epitaxial strain present in ultrathin films (<10 nm) and to preserve or tune the positive effects in films of thicknesses usually higher than 30 nm.

First-principles prediction of optoelectronic and thermoelectric properties of novel materials A2PdCl6 for Photovoltaic Applications

Lead-based organic-inorganic perovskites have demonstrated their excellent response to optoelectronic and solar cell applications. Their applications are limited because of the lead toxicity and instability of organic cations. Hence the primary objective of this research is to explore the potential of lead-free perovskite materials for their photovoltaic applications. In this study, DFT calculations are aimed at investigating structural, optoelectronic, and thermodynamic properties of A2BX6 (A = Cs, K &Rb; BPd; X = Cl) lead-free perovskites. The computed bond lengths and lattice constants agree with the reported experimental, and theoretical results. Our computed results of optoelectronic and thermoelectric properties of the title perovskites at the level of the most simple and straightforward approach “modified Becke Johnson (mBJ)” and “hybrid functional (HSE06)” methodology show that these materials are semiconductors with values of 2.28, 2.29, and 2.68 eV for K2PdCl6, Rb2PdCl6, and Cs2PdCl6, respectively. In addition, optical properties including optical conductivity, dielectric constant, and the coefficient of absorption are determined for radiation up to 10 eV. The distinctive optoelectronic characteristics of A2PdCl6 perovskites such as ideal band gaps, high dielectric constants, and optimal absorption values show their adeptness for designing the high-performance single junction and multi-junction perovskite solar cells.

Electrical and optical investigations lead-free Cesium Bismuth iodide single crystal

Extensive research efforts are currently focused on lead-free all-inorganic perovskite single crystals (SCs) due to their lower biological toxicity and improved material stability. These advancements address two significant obstacles in the implementation of practical device applications. Positive photoconductivity (PPC) under light illumination has been observed in lead-halide perovskite SCs. Given the optical activity of lead-free perovskites, it is anticipated that they will exhibit comparable characteristics. Nevertheless, we present in this study the discovery of negative photoconductivity (NPC) induced by light, coupled with a slow recovery method, in lead-free Cs3Bi2I9 perovskite material, which was successfully synthesized through the novel top-seed solution (TSS) process. In-depth investigations using femtosecond transient reflectance (fs-TR) spectroscopy demonstrate that these unique electronic transport characteristics originate from the generation of light-triggered trap states that are metastable within the perovskite crystal lattice. We computed the performance metrics of Cs3Bi2I9 SC detectors, encompassing detectivity (1.68 × 1012 Jones), responsivity (32 mA/W), and the current ratio (∼10257). The distinctiveness of these findings lies in the unique behavior of Cs3Bi2I9 SCs, which, despite being optically active, exhibit retroactive photocurrent upon irradiation. This behavior has rarely been observed in other lead-free perovskite materials.

Ab-initio calculation of halogen elements effect on the behavior of new double perovskite Cs2InSbX6 (X = F, Cl, Br, I): 1st part structural and optoelectronic properties

In recent years, there has been a growing fascination with lead-free perovskite materials, particularly in the realms of solar energy and photonics. It is imperative to conduct comprehensive theoretical investigations of these materials to effectively guide experimental pursuits. In this research, we harnessed the power of density functional theory (DFT) calculations, employing the Wien2k code, to delve into the distinctive characteristics of double-perovskite halides Cs2InSbX6 (X = F, Cl, Br, I). The viability and stability of their cubic structures were meticulously assessed, taking into consideration essential metrics such as the tolerance factor, octahedral factor and formation energy. Notably, the pronounced influence of spin–orbit coupling necessitated gap energy adjustments, achieved through a dual-pronged approach utilizing the generalized Perdew–Burke–Ernzerhof gradient approximation (PBE-GGA) and the modified Becke-Johnson (mBJ) exchange potential. The intricacies of band structure and state density were scrutinized using the GGA + mBJ method. The comprehensive findings elucidate that these compounds manifest fundamental electronic bandgaps spanning a range from 0.26 to 2.67 eV. Furthermore, they exhibit remarkably low carrier effective masses and a substantial degree of band dispersion. Of significance is the profound influence of halogen atom substitutions on their optical properties. Notably, a high absorption coefficient in the ultraviolet spectrum and the presence of a negative real dielectric function provide strong evidence for the adoption of metallic properties within a specific energy range. These compelling outcomes underscore the potential of these materials as highly promising candidates for a diverse array of photonic applications.

A study on defect, doping, and performance of ETLs (ZnO, TiO2, and IGZO) for the lead-free CsSnCl3 perovskite solar cell by SCAPS-1D framework

The potential of lead-free perovskite materials using cesium as an organic cation has been explored as a replacement for lead-based perovskite absorbers to minimize toxicity. These materials exhibit high stability, a tunable bandgap, and superior optoelectronic properties compared to lead-based materials. Extensive studies have investigated Sn-based cesium tin chloride (CsSnCl3) in the literature, focusing on multiple hole transporting layers (HTLs) and electron transporting layers (ETLs). A numerical study has been conducted to study the effects of thickness, series, and shunt resistance, as well as favorable band alignment with the absorber, HTL, and ETL layers. According to the literature, ETLs such as TiO2, ZnO, and IGZO, in combination with CBTS as the HTL, have emerged as the most promising candidates for achieving optimal fabrication of CsSbCl3 devices. However, several investigations have yet to be covered in the reports. These include analyzing the effects of absorber and interface defects on the ETLs/HTLs layers, determining the optimal metal back contact electrode, and optimizing the doping concentration of the absorber or ETLs/HTLs to achieve device optimization and the desired operating temperature. Through the optimization process, the study identified the optimum numerical values necessary to achieve higher device performance. It specifically found that ZnO performs the best as an ETL candidate, and the configuration combination of ITO/ZnO/(CsSnCI3)/CBTS/Se emerged as the most favorable compared to the values reported in the literature.

Unveiling the Structure-Luminescence-Stability relationship in 5s2-Based Antimony halides toward High-Performance emitters

Emerging low-dimensional metal halides have attracted enormous research interests due to their prominent photoluminescence (PL) properties and extensive application potentials. However, the systematic discussion on the structure-luminescence-stability relationship is still lacking. Herein, a series of novel lead-free metal halides are developed to unveil the underlying relationship. The as-synthesized (C6H5NH3)6SbCl9·H2O single crystal is structurally unstable that would spontaneously transform into (C6H5NH3)3ClSbCl5·H2O in the mother liquor, due to the strong antibonding Sb-5s2 lone pair with a spherical distribution in highly symmetrical geometry. To suppress this effect and stabilize the metastable phase, In3+ without ns electrons is introduced into the lattice of (C6H5NH3)6SbCl9·H2O, as a result, the changed coordination environment, including band structure, lattice constant and intermolecular electronic interaction, not only inhibits the structure transformation, but also leads to an enhanced PL efficiency (83.37 %) at ∼ 600 nm. This work promotes the understanding of structure-luminescence-stability relationship in organic–inorganic materials, and provides a new insight for further searching for high-performance lead-free perovskite luminescent materials.

1D Chiral Enantiomer Lead-Free Perovskites Induced Chiralopical Activity and Photoelectric Response.

Chirality is a fascinating geometrical concept with widespread applications in biology, chemistry, and materials. Incorporating chirality into hybrid perovskite materials can induce novel physical properties (chiral optical activity, nonlinear optics, etc.). Hybrid lead-free or lead-substituted perovskite materials, as representatives of perovskites, have been widely used in fields such as photovoltaics, sensors, catalysis, and detectors. However, the successful introduction of chirality into hybrid lead-free perovskites, which can enable their potential applications in areas such as circularly polarized light photodetectors, memories, and spin transistors, remains a challenging research topic. Here, we synthesized two new chiral lead-free perovskites, [(R)-2-methylpiperazine][BiI5] and [(S)-2-methylpiperazine][BiI5]. The material possesses a perovskite structure with a one-dimensional (1D) arrangement, denoted as ABX5. This structure is composed of chiral cations, specifically methylpiperazine, and endless chains of [BiI3] along the a-axis. These chains are assembled from distorted coplanar [BiI5]2- octahedra. The testing results revealed that (R)-1 and (S)-1 have narrow band gaps (Eg-R = 2.016 eV, Eg-S = 1.964 eV), high photoelectric response, and long carrier lifetime [R = 4.94 μs (τ), S = 7.85 μs (τ)]. It is worth noting that 1D chiral lead-free perovskites (R)-1 and (S)-1, which are synthesized in this study with narrow band gaps, high photoelectric response, and long carrier lifetime, have the potential to serve as alternative materials for the perovskite layer in future iterations of lead-free perovskite solar cells. Moreover, this research will inspire the preparation of multifunctional, lead-free perovskites.