Tin Halides Research Articles

Tin Halide Perovskites: From Fundamental Properties to Solar Cells.

Metal halide perovskites have unique optical and electrical properties, which make them an excellent class of materials for a broad spectrum of optoelectronic applications. However, it is with photovoltaic devices that this class of materials has reached the apotheosis of popularity. High power conversion efficiencies are achieved with lead-based compounds, which are toxic to the environment. Tin-based perovskites are the most promising alternative because of their bandgap close to the optimal value for photovoltaic applications, the strong optical absorption, and good charge carrier mobilities. Nevertheless, the low defect tolerance, the fast crystallization, and the oxidative instability of tin halide perovskites currently limit their efficiency. The aim of this review is to give a detailed overview of the crystallographic, photophysical, and optoelectronic properties of tin-based perovskite compounds in their multiple forms from 3D to low-dimensional structures. At the end, recent progress in tin-based perovskite solar cells are reviewed, mainly focusing on the detail of the strategies adopted to improve the device performances. For each subtopic, the current challenges and the outlook are discussed, with the aim to stimulate the community to address the most important issues in a concerted manner.

Large Grain Growth and Energy Alignment Optimization by Diethylammonium Iodide Substitution at A Site in Lead‐Free Tin Halide Perovskite Solar Cells

Environment‐friendly tin perovskite solar cells (T‐PKSCs) are the most suitable alternative candidate for lead‐free PKSCs. However, the photovoltaic performance of such T‐PKSCs is far below those of lead‐based perovskite solar cells due to an energetic mismatch between the perovskite layer and charge transport layers. Herein, it is shown that, by partial substitution of the A‐site cation using diethylammonium iodide (DEAI) substitution, deeper energy levels are obtained. At the same time, the trap density is reduced and the grain size is significantly improved. The fabricated solar cell shows much enhanced efficiency from 7.31% to 10.28%, short‐circuit current density from 18.68 to 21.69 mA cm−2, open‐circuit voltage from 0.59 to 0.67 V, and fill factor from 0.67 to 0.71 after DEAI substitution. Such an efficiency improvement can be explained by matching energy levels at the interfaces between perovskite layer and the charge transport layers. In addition, after 50 days of storage, the modified T‐PKSCs demonstrate high stability maintaining 78% of its initial efficiency, whereas the reference device degrades to 68% during 28 days storage.

Controlling Quantum-Well Width Distribution and Crystal Orientation in Two-Dimensional Tin Halide Perovskites via a Strong Interlayer Electrostatic Interaction.

Two-dimensional (2D) tin halide perovskites have recently emerged as very promising materials for eco-friendly lead-free photovoltaic devices. However, the fine control of the bulky organic cations orderly embedding into the perovskite structure with a narrow quantum-well width distribution and favorable orientation is rather complicated. In this study, we proposed to introduce the F-substituted phenylethlammonium (PEA) cation (i.e., 4-fluorophenethylammonium FPEA) in 2D tin halide perovskite, which may mitigate phase polydispersity and crystal orientation, thus potentially increasing attainable charge-carrier mobility. A strong interlayer electrostatic attraction between electron-deficient F atoms and its adjacent phenyl rings aligns the crystal structure, working together with the validated dipole interaction. Therefore, the fluorination of organic cation leads to orderly self-assembly of solvated intermediates and promotes vertical crystal orientation. Furthermore, the interlayer electrostatic interaction serves as a supramolecular anchor to stabilize the 2D tin halide perovskite structure. Our work uncovers the effect of interlayer molecular interaction on efficiency and stability, which contributes to the development of stable and efficient low-toxicity perovskite solar cells.

The Evolution of Photoluminescence Properties of PEA2SnI4 Upon Oxygen Exposure: Insight into Concentration Effects

AbstractThe time evolution of the photoluminescence properties in phenylethylammonium tin halide perovskite (PEA2SnI4) film as a function of oxygen concentration is reported. Photo‐brightening and reversible photoluminescence quenching are observed in PEA2SnI4 film at ultralow oxygen concentration (< 1.5 vol%). In the case of 1.5 vol% < [O2] < 21 vol%, the photoluminescence emission of PEA2SnI4 film can be partially recovered after resetting the samples to nitrogen box. As the oxygen concentration further increases with the range of 21 to 95 vol%, the photoluminescence emission of PEA2SnI4 film is significantly quenched and can only be slightly recovered after removing it to the nitrogen box. By correlating the material characterizations and theoretical analysis, the interactions between PEA2SnI4 and oxygen contain physisorption and chemical reactions are illustrated. Depending on the oxygen concentration, the chemical reactions between PEA2SnI4 and oxygen can be reversible and/or irreversible. The insights into oxygen concentration effects provide a guideline to optimize the stability of PEA2SnI4 for achieving high‐performance optoelectronic devices.

Advances and Challenges in Tin Halide Perovskite Nanocrystals

A major application limit for lead halide perovskite nanocrystals (NCs) is the presence of the highly toxic lead element, raising critical concerns of environmental pollution and health problems. To address this issue, tin halide perovskite NCs have been pushed to the forefront of perovskite research owing to their eco-friendly merit and tantalizing photophysical properties. In this Review, we critically summarize and assess the latest advances in the synthesis approaches of tin halide perovskite NCs including the hot injection, ligand-assisted reprecipitation, and chemical vapor deposition. More specifically, we detail the state-of-the-art preliminary studies in modulating their photophysical properties and in enhancing the stability with a variety of strategies such as precursor engineering, ligand engineering, and alloyed structure construction. Finally, we highlight the remaining challenges that need to be overcome to attain tin halide perovskite NCs with clear structure–property relationships and comparable physical and chemical properties to their lead-based cousins.

Enhancing Performance and Stability of Tin Halide Perovskite Light Emitting Diodes via Coordination Engineering of Lewis Acid–Base Adducts

AbstractFor resolving toxicity issues of Pb‐based perovskites, Sn‐based perovskites have been widely studied as a promising alternative due to similar valence electron configuration between Sn2+ and Pb2+. However, desired Sn2+ in the precursor solution and film is easily oxidized to Sn4+, causing detrimental Sn vacancies and impurities in the films. Unfortunately, dimethyl sulfoxide, a ubiquitously used Lewis base for the fabrication of high‐quality perovskite thin films via the adduct approach, further accelerates the oxidation of Sn2+ in the precursor solution. Herein, N,N′‐dimethylpropyleneurea (DMPU) is proposed as an alternative Lewis base for the fabrication of high‐quality Sn‐based perovskite thin films. The strongly coordinating Lewis base DMPU is shown to suppress the oxidation of Sn2+ in the precursor solution while promoting growth of uniform and highly crystalline thin films. The PEA2SnI4 perovskite light emitting diode (PeLED) based on DMPU demonstrates dramatically improves luminance (L): a more than sixfold enhanced external quantum efficiency (EQE) and better operational stability than those of the device fabricated without DMPU. The optimum PeLED based on DMPU achieves a maximum L and EQE of 68.84 cd m−2 and 0.361%, respectively. This study provides an important methodological base for studying Sn perovskites for development of high‐performance and eco‐friendly PeLEDs.

Tin(II) Acetylacetonate as a New Type of Tin Compensator Additive for Tin-Based Perovskite Solar Cells.

Tin (Sn)-based perovskite is one of the most promising candidates for lead (Pb)-free perovskite light-absorbing materials applied in solar cells. However, the intrinsic Sn vacancy (VSn) defects seriously hinder the device performance, making the reported maximum power efficiency (PCE) of Sn-based perovskite solar cells (PSCs) far behind those of Pb-based ones. During the study, SnF2 has been demonstrated as an indispensable Sn compensator additive to improve the device performance. Considering that the default use of SnF2 and the selection of a Sn compensator has also been limited to tin(II) halides, i.e., SnCl2, SnBr2, and SnI2, the role and work mechanism of the Sn compensator have not yet been clarified clearly. Herein, a new type of Sn compensator, tin(II) acetylacetonate [Sn (acac)2], is introduced into Sn-based PSCs. It is found that in addition to tin compensation, the organic ligand acac- can coordinate with Sn2+ in the precursor solution and improve the crystallization process of perovskites. Consequently, the maximum PCE of formamidinium tin triiodide (FASnI3) solar cells is enhanced from 3.88 to 7.27% using Sn (acac)2 as the Sn compensator.

Suppression of Sn2+/Sn4+ oxidation in tin-based perovskite solar cells with graphene-tin quantum dots composites in active layer

Tin (Sn) halide perovskite has been a promising candidate in lead-free perovskite solar cells (PSCs), but its chemical instability attributed to Sn2+/Sn4+ oxidation reduces device performance and stability. To address this problem, we propose a new approach, i.e. fabrication of mesoporous n-i-p Sn-based PSCs with the photoactive composite made of mixed-organic-cation Sn halide perovskite and reduced graphene oxide (rGO) sheets anchored with Sn quantum dots (i.e., FA0.8MA0.2SnI3/rGO-Sn QDs). The rGO-Sn QDs in active layer not only suppress the destructive Sn2+/Sn4+oxidation and recombination but also accelerate charge transport, improve charge-carrier lifetime and reduce trap state density. Compared to the power conversion efficiency (PCE) of Sn-PSC without Sn QDs, the composite-basted champion device showed 55% increase in efficiency, attributed to strong suppression of Sn2+/Sn4+oxidation and recombination. Furthermore, the champion device showed remarkable reproducibility and stability improvement, representing an essential step for the practical use of low-cost and lead-free PSCs.

Controlling the Crystallization Kinetics of Lead‐Free Tin Halide Perovskites for High Performance Green Photovoltaics

AbstractTin halide perovskites are promising candidates for lead‐free perovskite solar cells (PSCs) not only due to their low‐toxicity, but also due to their ideal energy bandgap, high charge carrier mobility, and long hot carrier lifetime. The certified efficiency of tin halide PSCs has now reached over 10%, but this is still far from the theoretical expectation. Much of the efficiency gap relates to the poor quality of tin halide perovskite films due to the lack of in‐depth understanding about the crystal nucleation and growth mechanisms for such films. This recognition motivates the present review, which is focused on the crystallization kinetics of tin halide perovskites. In particular, starting from a germane discussion on crystal nucleation and growth theories, several methods that have been used for controlling the rapid crystallization of tin halide perovskites are dissected. Finally, the current challenges and prospects for tin halide PSCs are presented. This comprehensive review summarizes and illuminates the parameter space for the optimization of tin halide perovskite film quality, promoting the future development of ecofriendly PSCs with high efficiency and high stability.

A Facile and Effective Ozone Exposure Method for Wettability and Energy-Level Tuning of Hole-Transporting Layers in Lead-Free Tin Perovskite Solar Cells.

Lead-free perovskite solar cells (PSCs) have attracted interest among scientists searching for eco-friendly energy harvesting devices. Herein, the effects of ozone exposure on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) in lead-free tin halide PSCs as a facile and low-cost process for improving device performance are analyzed. Two types of tin-based PSCs and one typical lead-based PSC were fabricated. The ozone exposure on PEDOT:PSS increases the short-circuit current density (JSC) and the fill factor (FF) of PSCs in all cases with perovskite grain enlargement and hole-mobility enhancement of the devices, respectively. For open-circuit voltage (VOC), the outcome depends on the band gap and the energy levels of the perovskite films. While ozone exposure treatment is favorable for PEA0.15FA0.85SnI3-based tin PSCs, VOC decreases with ozone exposure in the case of Ge:EDA0.01FA0.98SnI3-based tin PSCs because of a misalignment of the energy levels. Regardless, the efficiency of PEA0.15FA0.85SnI3-based tin PSCs increases from 8.7 to 10.1% when measured inside a glovebox upon ozone exposure of PEDOT:PSS. The efficiency of Ge:EDA0.01FA0.98SnI3-based tin PSCs increases from 6.8 to 8.1%, and the devices retain an efficiency of 5.0% even after 50 days in air.

Crystal structures and phase transitions of the methylammonium tin halide perovskites

Crystal structures and phase transitions of the methylammonium tin halide perovskites

Revealing Ultrafast Charge-Carrier Thermalization in Tin-Iodide Perovskites through Novel Pump-Push-Probe Terahertz Spectroscopy.

Tin-iodide perovskites are an important group of semiconductors for photovoltaic applications, promising higher intrinsic charge-carrier mobilities and lower toxicity than their lead-based counterparts. Controllable tin vacancy formation and the ensuing hole doping provide interesting opportunities to investigate dynamic intraband transitions of charge carriers in these materials. Here, we present for the first time an experimental implementation of a novel Optical-Pump–IR-Push–THz-Probe spectroscopic technique and demonstrate its suitability to investigate the intraband relaxation dynamics of charge carriers brought into nonequilibrium by an infrared “push” pulse. We observe a push-induced decrease of terahertz conductivity for both chemically- and photodoped FA0.83Cs0.17SnI3 thin films and show that these effects derive from stimulated THz emission. We use this technique to reveal that newly photogenerated charge carriers relax within the bands of FA0.83Cs0.17SnI3 on a subpicosecond time scale when a large, already fully thermalized (cold) population of charge-carriers is present. Such rapid dissipation of the initial charge-carrier energy suggests that the propensity of tin halide perovskites toward unintentional self-doping resulting from tin vacancy formation makes these materials less suited to implementation in hot-carrier solar cells than their lead-based counterparts.

Jorge Pascual

Angewandte ChemieVolume 133, Issue 39 p. 21267-21267 Introducing …Free Access Jorge Pascual Jorge Pascual First published: 07 August 2021 https://doi.org/10.1002/ange.202109997AboutSectionsPDF ToolsRequest permissionAdd to favorites ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract “Modern science needs to focus on making commodities available to everyone in a sustainable way … My favorite example of science in everyday life is weather …” Find out more about Jorge Pascual in his Introducing … Profile. Jorge Pascual The author presented on this page has published his first article as a submitting corresponding author in Angewandte Chemie: “Fluoride Chemistry in Tin Halide Perovskites”: J. Pascual, M. Flatken, R. Félix, G. Li, S.-H. Turren-Cruz, M. H. Aldamasy, C. Hartmann, M. Li, D. Di Girolamo, G. Nasti, E. Hüsam, R. G. Wilks, A. Dallmann, M. Bär, A. Hoell, A. Abate, Angew. Chem. Int. Ed. 2021, 60, doi.org/10.1002/anie.202107599; Angew. Chem. 2021, 133, doi.org/10.1002/ange.202107599. Position: Postdoctoral researcher, Helmholtz-Zentrum Berlin (Germany) Homepage: https://www.helmholtz-berlin.de/pubbin/vkart.pl?v=nnuyk ORCID: orcid.org/0000-0001-6486-0737 Education: 2010–2015 Bachelor and Masters in Chemistry, University of the Basque Country (Spain) 2019 PhD with Juan Luis Delgado and Ramón Tena-Zaera, University of the Basque Country (Spain) Since 2019 Postdoctoral researcher with Antonio Abate, Helmholtz-Zentrum Berlin (Germany) Research: Perovskites, materials chemistry, solution processing and characterization, NMR spectroscopy Hobbies: Trekking, swimming, languages, politics I am waiting for the day when someone will discover cures for neurodegenerative diseases. The biggest challenge facing my generation of scientists is to rebuild the trust of society in science among fast-spreading lies. My favorite example of science in everyday life is weather. Modern science needs to focus on making commodities available to everyone in a sustainable way. I chose chemistry as a career because I was always interested in the composition of things and their manipulation. The most important factor in the choice of my current research topic was how relatively unexplored its chemistry was. A key experience in my education was realizing how much interest every piece of knowledge has. The next big goal of my research is to improve the processability of tin-based perovskites to attract more interest to them. I recharge my batteries by playing an Age of Empires II match. The advice I wish I had received is to not be afraid of taking any decision as long as the intentions were good. My biggest motivation is the tremendously positive impact that developing a scientific culture has on societies. I celebrate success by sharing some drinks and food with my colleagues. The most important quality of a role model is empathy. In retrospect I would never again criticize any idea non-constructively. My favorite science broadcast is Órbita Laika from the Spanish public TV. Behind the Science References 1One of the most important characteristics of a scientist is to be observing. When we started working with tin perovskite solutions, we observed very pronounced optical changes with little modifications. We started measuring some samples with SnF2 just for curiosity, but we would have never thought that it was having such a strong influence in DMSO-based solutions. The nicest part of this work was how we arranged the combination of very different types of expertise, with several solution and film characterization techniques. I hope this work will help highlighting the need for more solution design and characterization. Google Scholar Volume133, Issue39September 20, 2021Pages 21267-21267 This is the German version of Angewandte Chemie. Note for articles published since 1962: Do not cite this version alone. Take me to the International Edition version with citable page numbers, DOI, and citation export. We apologize for the inconvenience. ReferencesRelatedInformation

Phase Evolution in Lead-Free Cs-Doped FASnI3 Hybrid Perovskites and Optical Properties

Tin halide perovskites are among the candidates having potential to substitute lead-based perovskites due to their environmentally benign components and potential medical usage. Nevertheless, the air stability remains a challenge due to Sn2+ oxidation. The recent developments have shown that adding SnF2 as an additive and A-site cation replacement by an inorganic element such as Cs+ can improve the film stability. However, exploring the structural change through A-site doping in Sn-based perovskites experimentally requires an in-depth investigation. Here, the phase evolution mechanism from the transformation of CsxFA1–xSnI3 to Cs2SnI6 via Cs2–xFAxSnI6 in the presence of the intermediate phase SnI2–(dmf)x due to Cs substitution in FASnI3 and the substitution’s influences on the optical properties were identified and investigated. Introducing a small amount of Cs+ (≤5% CsI) significantly promoted Sn2+ oxidation due to the anharmonic lattice dynamics. Later, at 10% CsI, self-doping was initiated, resulting in the coexistence of Sn2+/Sn4+. However, phase separation of Cs2SnI6 via Cs2–xFAxSnI6 occurred at contents greater than 10% CsI. Notably, the absorption coefficient was amplified along with the increasing Cs content (at 10% CsI, 6 times greater than that of FASnI3). The air stability was also enhanced as a result of Cs substitution. This work demonstrates the structural engineering of A-site cations in order to obtain various material properties for photovoltaic (PV) and non-PV applications.

Uncovering Halogen Mixing and Octahedral Dynamics in Cs2SnX6 by Multinuclear Magnetic Resonance Spectroscopy

Cs2SnX6 (X = Cl, Br, and I) compounds have emerged as promising lead-free and ambient-stable materials for photovoltaic and optoelectronic applications. To advance these promising materials, it is crucial to determine the correlations between physical properties and their local structure and dynamics. Solid-state NMR spectroscopy of multiple NMR-active nuclei (133Cs, 119Sn, and 35Cl) in these cesium tin(IV) halides has been used to reveal the atomic structure, which plays a key role in the materials’ optical properties. The 119Sn NMR chemical shifts span approximately 4000 ppm, and the 119Sn spin-lattice relaxation times span 3 orders of magnitude when the halogen goes from chlorine to iodine in these diamagnetic compounds. Moreover, ultrawideline 35Cl NMR spectroscopy of Cs2SnCl6 indicates an axially symmetric chlorine electric field gradient tensor with a large quadrupolar coupling constant of ca. 32 MHz, suggesting the presence of a chlorine moiety that is directly attached to Sn(IV) ions. Variable-temperature 119Sn spin-lattice relaxation time measurements support the presence of dynamics of octahedral SnI6 units in Cs2SnI6. We further show that complete mixed-halide solid solutions of Cs2SnClxBr6–x and Cs2SnBrxI6–x (0 ≤ x ≤ 6) form at any halogen compositional ratio. 119Sn and 133Cs NMR spectroscopy resolve the unique local SnClnBr6–n and SnBrnI6–n (n = 0–6) octahedral and CsBrmI12–m (m = 0–12) cuboctahedral environments in the mixed-halide samples. The experimentally observed 119Sn NMR results are consistent with magnetic shielding parameters obtained by density functional theory computations that were obtained to model the random halogen distribution in mixed-halide analogues. Finally, we demonstrate the difference in the local structures and the optical absorption properties of Cs2SnI6 samples prepared by solvent-assisted and solvent-free synthesis routes.

Fluoride Chemistry in Tin Halide Perovskites

Tin is the frontrunner for substituting toxic lead in perovskite solar cells. However, tin suffers the detrimental oxidation of SnII to SnIV. Most of reported strategies employ SnF2 in the perovskite precursor solution to prevent SnIV formation. Nevertheless, the working mechanism of this additive remains debated. To further elucidate it, we investigate the fluoride chemistry in tin halide perovskites by complementary analytical tools. NMR analysis of the precursor solution discloses a strong preferential affinity of fluoride anions for SnIV over SnII, selectively complexing it as SnF4. Hard X‐ray photoelectron spectroscopy on films shows the lower tendency of SnF4 than SnI4 to get included in the perovskite structure, hence preventing the inclusion of SnIV in the film. Finally, small‐angle X‐ray scattering reveals the strong influence of fluoride on the colloidal chemistry of precursor dispersions, directly affecting perovskite crystallization.

Ionic Liquid Stabilizing High‐Efficiency Tin Halide Perovskite Solar Cells

AbstractTin halide perovskites attract incremental attention to deliver lead‐free perovskite solar cells. Nevertheless, disordered crystal growth and low defect formation energy, related to Sn(II) oxidation to Sn(IV), limit the efficiency and stability of solar cells. Engineering the processing from perovskite precursor solution preparation to film crystallization is crucial to tackle these issues and enable the full photovoltaic potential of tin halide perovskites. Herein, the ionic liquid n‐butylammonium acetate (BAAc) is used to tune the tin coordination with specific O…Sn chelating bonds and NH…X hydrogen bonds. The coordination between BAAc and tin enables modulation of the crystallization of the perovskite in a thin film. The resulting BAAc‐containing perovskite films are more compact and have a preferential crystal orientation. Moreover, a lower amount of Sn(IV) and related chemical defects are found for the BAAc‐containing perovskites. Tin halide perovskite solar cells processed with BAAc show a power conversion efficiency of over 10%. This value is retained after storing the devices for over 1000 h in nitrogen. This work paves the way toward a more controlled tin‐based perovskite crystallization for stable and efficient lead‐free perovskite photovoltaics.

One-Step Synthesis of SnI2·(DMSO)x Adducts for High-Performance Tin Perovskite Solar Cells.

Contemporary thin-film photovoltaic (PV) materials contain elements that are scarce (CIGS) or regulated (CdTe and lead-based perovskites), a fact that may limit the widespread impact of these emerging PV technologies. Tin halide perovskites utilize materials less stringently regulated than the lead (Pb) employed in mainstream perovskite solar cells; however, even today's best tin-halide perovskite thin films suffer from limited carrier diffusion length and poor film morphology. We devised a synthetic route to enable in situ reaction between metallic Sn and I2 in dimethyl sulfoxide (DMSO), a reaction that generates a highly coordinated SnI2·(DMSO)x adduct that is well-dispersed in the precursor solution. The adduct directs out-of-plane crystal orientation and achieves a more homogeneous structure in polycrystalline perovskite thin films. This approach improves the electron diffusion length of tin-halide perovskite to 290 ± 20 nm compared to 210 ± 20 nm in reference films. We fabricate tin-halide perovskite solar cells with a power conversion efficiency of 14.6% as certified in an independent lab. This represents a ∼20% increase compared to the previous best-performing certified tin-halide perovskite solar cells. The cells outperform prior earth-abundant and heavy-metal-free inorganic-active-layer-based thin-film solar cells such as those based on amorphous silicon, Cu2ZnSn(S/Se)4 , and Sb2(S/Se)3.

Tin Halide Perovskite Polycrystalline Films Formed with Nonhazardous 2-Propanol Solvent

The use of safe and environmentally friendly materials is an important issue for industrial mass production processes. In this study, we demonstrate the deposition of tin halide perovskite films using environmentally benign 2-propanol as a solvent. Sequential deposition of 2-propanol solutions containing SnBr2 and CH3NH3I led to the formation of CH3NH3SnBr3−xIx, which exhibited good crystallinity and visible-light absorption.

Role of Polyhedron Unit in Distinct Photophysics of Zero-Dimensional Organic-Inorganic Hybrid Tin Halide Compounds.

The zero-dimensional (0D) metal halides comprising isolated metal-halide polyhedra are the smallest inorganic quantum systems and accommodate quasi-localized Frenkel excitons with unique photophysics of broadband luminescence, huge Stokes shift, and long lifetime. Little is known about the role of polyhedron type in the characteristics of 0D metal halides. We comparatively study three novel kinds of 0D hybrid tin halides having identical organic groups. They are efficient light emitters with a maximal quantum yield of 92.3%. Their most stable phases are composed of octahedra for the bromide and iodide but disphenoids for the chloride. They separately exhibit biexponential and monoexponential luminescence decays due to different symmetries and electronic structures. The chloride has the largest absorption and smallest emission photon energies. A proposed model regarding unoccupied-energy-band degeneracy explains well the experimental phenomena and reveals the crucial role of polyhedron type in determining optical properties of the 0D tin halides.