Sn-based Perovskites Research Articles

Synergetic Regulation of Interface Defects and Carriers Dynamics for High-Performance Lead-Free Perovskite Solar Cells.

Severe nonradiative recombination and open-circuit voltage loss triggered by high-density interface defects greatly restrict the continuous improvement of Sn-based perovskite solar cells (Sn-PVSCs). Herein, a novel amphoteric semiconductor, O-pivaloylhydroxylammonium trifluoromethanesulfonate (PHAAT), is developed to manage interface defects and carrier dynamics of Sn-PVSCs. The amphiphilic ionic modulators containing multiple Lewis-base functional groups can synergistically passivate anionic and cationic defects while coordinating with uncoordinated Sn2+ to compensate for surface charge and alleviate the Sn2+ oxidation. Especially, the sulfonate anions raise the energy barrier of surface oxidation, relieve lattice distortion, and inhibit nonradiative recombination by passivating Sn-related and I-related deep-level defects. Furthermore, the strong coupling between PHAAT and Sn perovskite induces the transition of the surface electronic state from p-type to n-type, thus creating an extra back-surface field to accelerate electron extraction. Consequently, the PHAAT-treated device exhibits a champion efficiency of 13.94% with negligible hysteresis. The device without any encapsulation maintains 94.7% of its initial PCE after 2000h of storage and 91.6% of its initial PCE after 1000h of continuous illumination. This work provides a reliable strategy to passivate interface defects and construct p-n homojunction to realize efficient and stable Sn-based perovskite photovoltaic devices.

Stable two-dimensional tin-based perovskites for warm-white light emitters

Two-dimensional (2D) Sn-based organic-inorganic hybrid perovskites are useful materials for white light emitters due to their super high fluorescence efficiency and higher stability when compared to their three-dimensional (3D) counterparts. Herein, 2D Ruddlesden-Popper (RP) perovskites (BA)2Sn(Br1-x Ix)4 (BA = n-butylammonium, x: 0–1) were prepared and regulated using halogen doping. As iodine content increased, the band gap of (BA)2Sn(Br1-xIx)4 was finely regulated from 2.35 eV to 2.0 eV, thereby tuning the photoluminescence from yellow to red with relatively high PLQY exceeding 40 %. The use of small amounts of Pb2+ to stabilize Sn2+ through the addition of PbO in the precursor solution resulted in high air- and photo stable (BA)2Pb0.1Sn0.9(Br–I)4 phosphors with bright yellow to red light. The mixture with (BA)2PbBr4 (blue light phosphor) followed by excitement by UV LED chips (285 nm) resulted in cold and warm white Sn–Br–I perovskite LEDs. The CIE coordinates and correlated color temperature (CCT) indicated Br0.4I0.6 LED as an ideal warm-white emitter with suitable CIE (0.352, 0.330) and CCT (4376.3 K). The prepared white LEDs showed high photo and air stability without significant luminescence decay (<5 % relative) under continuous UV light excitation over 200 min and exposure to air for 3 months.

First-principles calculations to investigate structural, optoelectronic and thermoelectric properties of Sn-based halide perovskites: CsSnCl3 and CH3NH3SnCl3

First-principles calculations to investigate structural, optoelectronic and thermoelectric properties of Sn-based halide perovskites: CsSnCl3 and CH3NH3SnCl3

Inhibition of Sn2+ Oxidation in FASnI3 Perovskite Precursor Solution and Enhanced Stability of Perovskite Solar Cells by Reductive Additive.

Tin-based halide perovskite solar cells (Sn-PSCs) have attracted a progressive amount of attention as a potential alternative to lead-based PSCs (Pb-PSCs). Sn-perovskite films are fabricated by a solution process spin-coating technique. However, the efficiency of these devices varies significantly with the different batches of precursor solution due to the poor chemical stability of SnI2-DMSO and the oxidation of Sn2+ to Sn4+. This study investigated the origin of Sn2+ oxidation before film formation, and it was identified that the ionization of SnI2 in dimethyl sulfoxide (DMSO) causes the oxidation of free Sn2+ and I- ions. To address these issues, this study introduces the reductive additive 4-fluorophenylhydrazine hydrochloride (4F-PHCl) in the FASnI3 perovskite precursor solution. The hydrazine functional (-NH-NH2) group converted detrimental Sn4+ and I2 defects back to Sn2+ and I- in precursor solution while retaining the properties of the perovskite solution. Furthermore, the addition of 4F-PHCl in the precursor solution effectively slows the crystallization process, enhancing the crystallinity of FASnI3 perovskite films and guaranteeing the Sn2+/I- stoichiometric ratio, ultimately leading to a power conversion efficiency (PCE) of 10.86%. The hydrophobic fluorinated benzene ring in 4F-PHCl ensures moisture stability in perovskite films, allowing unencapsulated PSCs to retain over 92% of their initial PCE in an N2-filled glovebox for 130 days. Moreover, the 4F-PHCl-modified encapsulated PSCs showed superior operational stability for 420 h and maintained 95% of their initial PCE for 300 h under maximum power point tracking at 1 sun continuous illumination. This study's findings provide a promising pathway to create a controlled Sn-based perovskite precursor solution for highly reproducible and stable Pb-free Sn-PSCs.

Unlocking the Potential of Tin-Based Perovskites: Properties, Progress, and Applications in New-Era Electronics.

Electronics have greatly promoted the development of modern society and the exploration of new semiconducting materials with low cost and high mobility continues to attract interest in the advance of next-generation electronic devices. Among emerging semiconductors, the metal-halide perovskite, especially the nontoxic tin (Sn)-based candidates, has recently made breakthroughs in the field of diverse electronic devices due to its excellent charge transport properties and cost-effective large-area deposition capability at low temperatures. To enable a more comprehensive understanding of this emerging research field and promote the development of new-generation perovskite electronics, this review aims to provide an in-depth understanding with the discussion of unique physical properties of Sn-based perovskites and the summarization of recent research progress of Sn-based perovskite field-effect transistors (FETs) and diverse electronic devices. The unique character of negligible ion migration is also discussed, which is fundamentally different from the lead-based counterparts and provides a great prerequisite for device application. The following section highlights the potential broad applications of Sn-perovskite FETs as a competitive and feasible technology. Finally, an outlook and remaining challenges are given to advance the progression of Sn-based perovskite FETs, especially on the origin and solution of stability problems toward high-performance Sn-based perovskite electronics.

A first-principles study to investigate the physical properties of Sn-based hydride perovskites XSnH3 (X = K, Li) for hydrogen storage application

Based on density functional theory, the present study used the Cambridge serial total energy package code to figure out the structural, electronic, magnetic, optical, and mechanical properties of perovskite hydrides XSnH3 (X = K, Li). The band gap, total density of states, and partial density of states of the hydrides under consideration have been calculated, confirming the metallic behavior via the overlapping of the conduction and valence bands with a zero-band gap. The XSnH3 lattice parameters, determined using generalized gradient approximations, are 4.3 Å for KSnH3 and 4.1 Å for LiSnH3. Both of these materials are found to be hard, antiferromagnetic, and anisotropic in nature. The Poisson's ratio indicates that LiSnH3 is brittle while KSnH3 is ductile. The B/G ratio also confirms the brittleness of LiSnH3 and the ductility of KSnH3. The hydrogen storage capacity of KSnH3 and LiSnH3 is calculated to be 1.88 wt % and 2.35 wt %. Both materials have the potential to store hydrogen, as evidenced by the storage properties, but it is determined that LiSnH3 is the superior material to utilize for use in applications involving hydrogen storage.

S-scheme heterojunction-mediated hydrogen production over the graphitic carbon nitride-anchored nickel stannate perovskite

A novel heterojunction between Sn-based perovskite and graphitic carbon nitride (gCN) is synthesized to achieve an enhanced spatial charge separation. The interfacial coupling between cube-shaped nickel tin oxide (NSO) and gCN is achieved through the surface sites in NSO. An improved hydrogen production rate of 646 µmol g−1 h−1 is measured in the composite (NSO-gCN), which is twice that in gCN, using triethanolamine (TEOA) and chloroplatinic acid (1% w/w) as holes scavenger and the precursor for the Pt cocatalyst, respectively. Such significant improvement in H2 production performance of the composite is benefited by the high reductive electrons generated via an S-scheme charge transfer pathway, as evidenced by radical trapping experiments and XPS elemental analysis. The composite shows good stability in hydrogen evolution, with marginal (3%) decrease measured in the materials activity after 5 cycles. This study provides an opportunity to develop an S-scheme heterojunction with the Sn-based perovskite anchored in gCN, as an alternative to Ti-based perovskite for various photocatalytic reactions.

Thermodynamic stability and electronic properties of 2D all-inorganic halogen perovskites

Two-dimensional (2D) all-inorganic metal halide perovskites capture more attentions due to its superior stability compared with three-dimensional (3D) perovskites. However, the power conversion efficiency of 2D all-inorganic perovskite is needed to be largely improved and few theoretical research focuses on its structural stability and optoelectronic properties in depth. Herein, we exploit the electronic structure, thermodynamically stable phase, effective masses, and optical properties of Ruddlesden-Popper (RP) 2D inorganic perovskites Csn+1MnIn+1Cl2n (M = Pb or Sn, n = 1–4 and ∞) by employing density functional theory calculations. It is found that the most stable configuration is closely related to the specific position of the halogen atoms. Moreover, the thermodynamic stability of Pb-based 2D perovskites is further calculated based on the phase diagram, which is notably more stable than that of Cs2SnI2Cl2. In addition, our calculated results show that the band gaps decrease as the number of layers increase in both Sn- and Pb-based perovskites. Moreover, Sn-based 2D perovskites can be adjusted to superior electronic properties with the optimal bandgap ranging from 0.9 to 1.6 eV and small effective mass of carriers considering its future application. This systematic theoretical study provides a significant methodology for fabricating stable, new-type 2D inorganic photoelectric materials according to a reasonable stoichiometric ratio.

Cation-Radius-Controlled Sn-O Bond Length Boosting CO2 Electroreduction over Sn-Based Perovskite Oxides.

Despite the intriguing potential shown by Sn-based perovskite oxides in CO2 electroreduction (CO2 RR), the rational optimization of their CO2 RR properties is still lacking. Here we report an effective strategy to promote CO2 -to-HCOOH conversion of Sn-based perovskite oxides by A-site-radius-controlled Sn-O bond lengths. For the proof-of-concept examples of Ba1-x Srx SnO3 , as the A-site cation average radii decrease from 1.61 to 1.44 Å, their Sn-O bonds are precisely shortened from 2.06 to 2.02 Å. Our CO2 RR measurements show that the activity and selectivity of these samples for HCOOH production exhibit volcano-type trends with the Sn-O bond lengths. Among these samples, the Ba0.5 Sr0.5 SnO3 features the optimal activity (753.6 mA ⋅ cm-2 ) and selectivity (90.9 %) for HCOOH, better than those of the reported Sn-based oxides. Such optimized CO2 RR properties could be attributed to favorable merits conferred by the precisely controlled Sn-O bond lengths, e.g., the regulated band center, modulated adsorption/activation of intermediates, and reduced energy barrier for *OCHO formation. This work brings a new avenue for rational design of advanced Sn-based perovskite oxides toward CO2 RR.

Mechanistic Understanding of Oxidation of Tin-based Perovskite Solar Cells and Mitigation Strategies.

Tin (Sn)-based perovskites as the most promising absorber materials for lead-free perovskite solar cells (PSCs) have achieved the record efficiency of over 14 %. Although suppressing the oxidation of Sn-based perovskites is a frequently concerned topic for Sn-based PSCs, many studies have given vague explanations and the mechanisms are still under debate. This is in principal due to the lack of an in-depth understanding of various and complex intrinsic and extrinsic factors causing the oxidation process. In this context, we critically review the chemical mechanism of facile oxidation of Sn-based perovskites and differentiate its detrimental effects at material- and device-level. More importantly, we classify and introduce the intrinsic factors (raw materials and solvent of perovskite precursors) and extrinsic factors (exposure to neutral oxygen and superoxide) causing the oxidation with their corresponding anti-oxidation improvement methods. The presented comprehensive understanding and prospect of the oxidation provide insightful guidance for suppressing the oxidation in Sn-based PSCs "from the beginning to the end".

14.31 % Power Conversion Efficiency of Sn-Based Perovskite Solar Cells via Efficient Reduction of Sn4.

The photoelectric properties of nontoxic Sn-based perovskite make it a promising alternative to toxic Pb-based perovskite. It has superior photovoltaic performance in comparison to other Pb-free counterparts. The facile oxidation of Sn2+ to Sn4+ presents a notable obstacle in the advancement of perovskite solar cells that utilize Sn, as it adversely affects their stability and performance. The study revealed the presence of a Sn4+ concentration on both the upper and lower surfaces of the perovskite layer. This discovery led to the adoption of a bi-interface optimization approach. A thin layer of Sn metal was inserted at the two surfaces of the perovskite layer. The implementation of this intervention yielded a significant decrease in the levels of Sn4+ and trap densities. The power conversion efficiency of the device was achieved at 14.31 % through the optimization of carrier transportation. The device exhibited operational and long-term stability.

Metal oxide nanoparticles as an electron-transport layer in perovskite solar cell

The research on the application of lead-free perovskite materials as an active layer in solar cells has been positively carried out for the last few years. Although the efficiency of lead-contained metal halide-based Perovskite has reached above 25%, but lead is a highly toxic substance that is hazardous to the environment, and this is one of the obstacles to their commercialization. In this article, a Sn-based Perovskite (CH3NH3SnI3) solar cell with two distinct electron transport layers was simulated using GPVDM (General Purpose Photovoltaic Device Model) and fabricated with a simple sol-gel method. Along with the absorber layer, the charge transport materials also play an essential role in extracting electrical power. The comparison of ZnO and TiO2 as electron collectors has been investigated and characterized, the hole-carrying layer has been eliminated for better findings. Remarkably, we achieve an efficiency of 7.33% and 6.75% in simulation and 6.90% and 5.81% from fabricated devices using ZnO and TiO2, respectively.

A Numerical Approach to Analysis of an Environment-Friendly Sn-Based Perovskite Solar Cell with SnO2 Buffer Layer Using SCAPS-1D

In this research, we have proposed a Sn-based perovskite solar cell using solar cell capacitance software. The main aim of this study is to develop an environment-friendly and highly efficient structure that can be used as an alternative to other toxic lead-based perovskite solar cells. This work performed a numerical analysis for the proposed (Al/ZnO/SnO2/CH3NH3SnI3/Ni) device structure. The absorber layer CH3NH3SnI3, buffer layer SnO2, and electron transport layer (ETL) ZnO, with aluminium as the front contact and nickel as the back contact, have been used in this simulation. Several analyses have been conducted for the proposed structure, such as the impact of the absorber layer thickness, acceptor density, defect density, series and shunt resistances, back contact work function, and operating temperature. The device simulation revealed that the optimum thickness of the absorber layer is 1.5 μm and 0.05 μm for the buffer layer. The proposed Sn-based perovskite structure has obtained a conversion efficiency of 28.19% along with FF of 84.63%, Jsc of 34.634 mA/cm2, and Voc of 0.961 V. This study shows the upcoming lead-free perovskite solar cell’s enormous potential.

Simulation of efficient Sn/Pb-based formamidinium perovskite solar cells with variation of electron transport layers

Numerical modelling on functional Sn-based perovskite solar cells (PSCs) has been performed and compared with Pb-based PSCs by using general-purpose photovoltaic device model software. The effect of variation in active layer thickness and various electron transport layers (ETLs), including tin oxide (SnO2), zinc oxide, C60, titanium dioxide, phenyl-C61- butyric acid methyl ester, on the photovoltaic parameters of Sn-based PSCs has been investigated. The active layer thickness was observed to be 500 nm, and SnO2 as ETL material resulted in the most efficient PSC. The optimized Sn-based device with formamidinium tin iodide as perovskite active layer shows promising results with a maximum power conversion efficiency of 24.41% compared to 27.49% for formamidinium lead iodide-based device. Further, other photovoltaic parameters for lead free PSC devices are quite comparable as for lead-based devices, showing the potential of Sn-based perovskite material as a fair candidate to replace toxic Pb-based-PSCs.

Passivating Grain Boundary Defects with Tris(hydroxymethyl)aminomethane to Achieve Efficient and Stable Tin-Based Perovskite Solar Cells

Although tin (Sn)-based perovskite is regarded as a good substitute for a lead-based analogue due to its environmental friendliness and suitable band gap, Sn-based perovskite solar cells (PSCs) still need to overcome practical stability and efficiency problems. Here, a passivation material tris(hydroxymethyl)aminomethane (THAM) with amino and multihydroxyl groups is added into the formamidinium tin iodide (FASnI3) perovskite to reduce the defect state density and unnecessary nonradiative recombination of the film, which eventually not only improves the light absorption ability and film crystallinity but also inhibits the oxidation of Sn2+. Applications of the THAM-doped FASnI3 perovskite films into PSCs acquire a high power conversion efficiency of 9.18%. Moreover, the storage stabilities of PSCs are obviously prolonged because of the improved Sn-based perovskite film quality, showing excellent stability of 550 h to keep 85% of its initial efficiency (in an N2 environment).

Efficient and stable energy conversion using 2D/3D mixed Sn-perovskite photovoltaics with antisolvent engineering

Sn-based organic-inorganic perovskite is a promising light harvesting material to replace toxic problematic Pb-based perovskite. However, surface morphology of 3-dimensional (3D) or 2D/3D mixed Sn-based perovskite structure is difficult to control owing to its very fast crystal growth. Thus, it is necessary to control Sn-based perovskite crystal growth for an efficient photovoltaic performance. In this regard, this work mainly focused on highly oriented crystal growth of 2D/3D mixed Sn-based perovskite structure using antisolvent engineering approach. The various antisolvents including anisole (AS), chlorobenzene (CB), toluene (TL), and diethyl ether (DE) were employed for formation of 2D/3D Sn-based perovskite film. The evaporation rate of antisolvents plays a key role to control the morphology of 2D/3D Sn-based perovskite by altering the nucleation and crystal growth. As a result, TL assisted perovskite film having compact morphology that exhibited best PCE of 8.78%. However, in case of DE, CB, and AS assisted perovskite films exhibited poor morphology due to faster or slower the evaporation rate of these antisolvents compared to TL. Therefore, the introduced approach provides an interesting insight on development of high quality 2D/3D mixed Sn-based perovskite film.

Ionic liquid functionalized tin halide perovskite investigated by STXM and spectro-ptychography

The structural and compositional properties of tin halide perovskites (CH(NH2)2SnI3, FASnI3) with and without an ionic liquid of 1-Ethyl-3-methylimidazolium bis(trifluormethylsulfonyl) imide (EMITFSI) were investigated using the scanning transmission soft X-ray microscopy (STXM) and spectro-ptychography techniques at the Sn M5,4-edge, I M5,4-edge, O K-edge, C K-edge, and N K-edge. The study offers a comprehensive interpretation of the spectral characteristics of main components (C, N, Sn, and I) in Sn-based perovskites through STXM-based techniques and further reveals differences between the perovskite samples with and without adding EMITFSI ionic liquid. The chemical imaging of Sn and I shows that the perovskite sample without ionic liquid has Sn-rich regions in iodine cavities, while the ionic liquid-treated sample exhibits a more homogeneous perovskite phase. Furthermore, the C and N K-edge XANES resonance features support the interaction between the non-volatile ionic liquid and FA+, thus playing a protective role in the formation and stabilization of perovskite phase.

Engineering Stable Lead-Free Tin Halide Perovskite Solar Cells: Lessons from Materials Chemistry.

Substituting toxic lead with tin (Sn) in perovskite solar cells (PSCs) is the most promising route toward the development of high-efficiency lead-free devices. Despite the encouraging efficiencies of Sn-PSCs, they are still yet to surpass 15% and suffer detrimental oxidation of Sn(II) to Sn(IV). Since their first application in 2014, investigations into the properties of Sn-PSCs have contributed to a growing understanding of the mechanisms, both detrimental and complementary to their stability. This review summarizes the evolution of Sn-PSCs, including early developments to the latest state-of-the-art approaches benefitting the stability of devices. The degradation pathways associated with Sn-PSCs are first outlined, followed by describing how composition engineering (A, B site modifications), additive engineering (oxidation prevention), and interface engineering (passivation strategies) can be employed as different avenues to improve the stability of devices. The knowledge about these properties is also not limited to PSCs and also applicable to other types of devices now employing Sn-based perovskite absorber layers. A detailed analysis of the properties and materials chemistry reveals a clear set of design rules for the development of stable Sn-PSCs. Applying the design strategies highlighted in this review will be essential to further improve both the efficiency and stability of Sn-PSCs.

2D Ruddlesden-Popper Sn-Based Perovskite Weak Light Detector for Image Transmission and Reflection Imaging.

2D Ruddlesden-Popper Sn-based perovskite has excellent optoelectronic properties and weak halide ion migration characteristics, making it an ideal candidate for weak light detection, which has great potential in light communication, and medical applications. Although Sn-based perovskite photodetectors are developed, weak light detection is not demonstrated yet. Herein, a high-performance self-powered photodetector with the capability to detect ultra-weak light signals is designed based on vertical PEA2 SnI4 /Si nanowires heterojunction. Due to the low dark current and high light absorption efficiency, the devices present a remarkable responsivity of 42.4mA W-1 , a high detectivity of 8 × 1011 Jones, and an ultralow noise current of 2.47 × 10-13 A Hz-1/2 . Especially, the device exhibits a high on-off current ratio of 18.6 at light signals as low as 4.60 nW cm-2 , revealing the capacity to detect ultra-weak light. The device is applied as a signal receiver and realized image transmission in light communication system. Moreover, high-resolution reflection imaging and multispectral imaging are obtained using the device as the sensor in the imaging system. These results reveal that 2D PEA2 SnI4 -based self-powered photodetectors with low-noise current possess enormous potential in future weak light detection.

Sn-Based Perovskite Solar Cells towards High Stability and Performance

Recent years have witnessed rapid development in the field of tin-based perovskite solar cells (TPSCs) due to their environmental friendliness and tremendous potential in the photovoltaic field. Most of the high-performance PSCs are based on lead as the light-absorber material. However, the toxicity of lead and the commercialization raise concerns about potential health and environmental hazards. TPSCs can maintain all the optoelectronic properties of lead PSCs, as well as feature a favorable smaller bandgap. However, TPSCs tend to undergo rapid oxidation, crystallization, and charge recombination, which make it difficult to unlock the full potential of such perovskites. Here, we shed light on the most critical features and mechanisms affecting the growth, oxidation, crystallization, morphology, energy levels, stability, and performance of TPSCs. We also investigate the recent strategies, such as interfaces and bulk additives, built-in electric field, and alternative charge transport materials that are used to enhance the performance of the TPSCs. More importantly, we have summarized most of the recent best-performing lead-free and lead-mixed TPSCs. This review aims to help future research in TPSCs to produce highly stable and efficient solar cells.