Pb Perovskite Research Articles

Optimizing Blade‐Coated Tin–lead Perovskite Solar Cells and Tandems with Multi‐Carboxyl and Amino Group Integration

AbstractMixed tin–lead (Sn–Pb) perovskites often face a daunting challenge: rapid and uncontrollable crystallization, leading to a plethora of defects and significant stress. This issue is particularly exacerbated during the blade‐coating preparation of scalable Sn–Pb perovskite films. In this study, a facile strategy involving the addition of ammonium citrate (AC) to narrow‐bandgap mixed Sn–Pb perovskite precursors is introduced. AC, armed with its arsenal of multiple carboxyl and amino groups, acts as a virtuoso conductor, orchestrating controlled crystal growth by harmonizing with Pb2+ and Sn2+ ions. This addition significantly boosts the crystallinity of the perovskite films, alleviates interface stress, inhibits Sn2+ oxidation, and mitigates interfacial defects. Consequently, The blade‐coated AC‐incorporated mixed Sn–Pb perovskite solar cells achieve a high photovoltaic conversion efficiency of nearly 21%. Furthermore, extending this strategy to two‐terminal all‐perovskite tandem solar cells yielded a remarkable maximum efficiency of 27.20%. This work presents an effective strategy for producing efficient blade‐coated mixed Sn–Pb perovskite solar cells, heralding a pathway toward scalable fabrication of all‐perovskite tandem solar cells.

Tin doping modulates electron-hole recombination in Dion-Jacobson phase 2D hybrid perovskite

To obtain less-toxic and optimal-band-gap perovskite materials, tin (Sn)-lead (Pb) hybrid technology comes into the sight of researchers. The Sn–Pb ratio primarily affects the electronic band structure, conductivity, and carrier transport, which are essential for optoelectronic performance. While most reports are about 3D materials, there has been little coverage of 2D Sn–Pb perovskites which exhibiting improved stability. In this paper, the e-h recombination dynamics in Dion-Jacobson Phase 2D Sn–Pb perovskites are studied using time-dependent ab initio nonadiabatic molecular dynamics (NAMD) simulation. It is found that Sn doping plays a significant role in narrowing the band-gap of 2D perovskites and localizing the charge distribution. Only a small amount of Sn doping can minimize NA coupling and shorten decoherence time of frontier orbitals simultaneously, then leading to longer charge recombination time. NAMD simulations reveal the optimal Sn ratio (25 mol%) and provide an effective way to design high-performance 2D perovskite materials.

Bimolecular Crystallization Modulation Boosts the Efficiency and Stability of Methylammonium‐Free Tin–Lead Perovskite and All‐Perovskite Tandem Solar Cells

AbstractThe elimination of methylammonium (MA) cation from mixed tin–lead (Sn–Pb) narrow‐bandgap (NBG) perovskites is an effective approach to enhance the operational stability of all‐perovskite tandem solar cells (TSCs). Unfortunately, the uncontrolled nucleation and crystallization processes of MA‐free Sn–Pb perovskites usually lead to inferior film quality and device performance. Herein, a bimolecular crystallization modulation strategy is reported by using guanidine thiocyanate (GuaSCN) and aminoacetamide hydrochloride (AHC) together as additives to improve the film quality of MA‐free Sn–Pb perovskites. It is demonstrated that the use of bimolecular additives can effectively improve the crystallinity, increase the grain size, and induce a preferred (100) orientation for the corresponding films, leading to high‐quality absorber with considerably reduced defect density and suppressed non‐radiative recombination. In addition, the bimolecular additives can reduce the self‐p‐doping hole concentration within the perovskite films and enhance the charge extraction at the perovskite/electron transport layer interface. The modified NBG perovskite solar cells deliver a power conversion efficiency (PCE) of 22.14%. Coupled with the wide‐bandgap (WBG) subcell, the all‐perovskite TSCs give a champion certified PCE of 27.15%, which is the highest certified PCE for MA‐free all‐perovskite TSCs. Encapsulated tandem devices maintain 90% of the initial PCE after 473 h operation.

Buried Interface Passivation of Sn–Pb Narrow‐Bandgap Perovskite for Highly Efficient All‐Perovskite Tandem Solar Cells

All‐perovskite tandem solar cells (ATSCs) present a remarkable opportunity to overcome the Shockley–Queisser efficiency limit of single‐junction solar cells. However, the stability of ATSCs significantly lags that of their pure Pb‐based single‐junction counterparts. Recent studies have identified that the widely used poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) hole transport layer in narrow‐bandgap (NBG) tin–lead (Sn–Pb) perovskite solar cells (PSCs) hinders the efficiency and stability. Herein, a patching strategy to optimize the interface between perovskite and PEDOT:PSS is proposed. Both theoretical and experimental studies reveal that PenA+ and Ac− can decrease defect states at the interface and strengthen the binding between PEDOT:PSS and Sn–Pb perovskite. Furthermore, the pentylammonium acetate (PenAAc) interlayer improves carrier extraction and suppresses the oxidation of Sn2+ to Sn4+. With the PenAAc buried layer, the fabricated NBG PSCs obtain an impressive power conversion efficiency (PCE) of 21.86%, along with significantly enhanced device stability. By integrating the buried passivated NBG Sn–Pb perovskite with a 1.75 eV wide‐bandgap PSC, the two‐terminal ATSC achieves a PCE of 26.54%. This work provides a valuable approach to fabricate efficient and stable NBG PSCs.

Optical properties of lead-free Cs3Bi2I9 nanowire arrays prepared by template

Bismuth-based (Bi) perovskites have garnered significant interest as alternatives to lead-based (Pb) perovskites in photoelectric applications due to their non-toxicity and diverse structural properties. However, the inherent high limitation of electrons presents a significant challenge to their further utilization in various applications. Herein, all-inorganic Cs3Bi2I9 nanowire arrays have been successfully prepared by AAO template combined with the two-step method of low-temperature solution. Compared to the Cs3Bi2I9 film, the Cs3Bi2I9 nanowire arrays obtained the higher photoluminescence intensity, indicating a strong interaction between Cs3Bi2I9 and AAO, resulting from the significant weakening of the high electron confinement in the valence band of Cs3Bi2I9, which presenting as the valence band of the Cs3Bi2I9-AAO is mainly contributed by the O 2p orbital, while the conduction band does not change significantly. In addition, the Cs3Bi2I9 nanowire arrays have been demonstrated with the enhanced environmental and thermal stability, which maintain 90 % of their initial photoluminescence intensity after 120 h (in a vacuum) heating at 80 °C or after 10 days in the air (relative humidity of 40 %).

A Ferrocene Capping Layer Enabling Highly Efficient and Stable Sn–Pb Mixed Perovskite Solar Cells

The Sn–Pb mixed perovskite with a narrow bandgap is essential for the construction of all‐perovskite tandem solar cells. However, the oxidation of Sn2+ to Sn4+ makes the fabrication of Sn–Pb perovskite solar cells (PSCs) challenging. Herein, a ferrocene (Fc) capping layer is introduced on the surface of Sn–Pb mixed perovskite to maintain a reducing environment. This is due to a strong electron supply capacity from the π‐orbitals in cyclopentadiene in Fc, which effectively suppresses the oxidation of Sn2+, reduces the defect density, and leads to an improvement in carrier lifetime. Therefore, the Fc capping layer significantly improves the power conversion efficiency (PCE) of single‐junction Sn–Pb PSCs from 17.49% to 21.02%. It maintains 87% of its initial PCE after light exposure at 1 sun condition in N2 atmosphere for 288 h, demonstrating good long‐term stability. The strategy outlined herein offers a straightforward and efficient approach to enhance the stability and PCE of narrow‐bandgap Sn–Pb mixed PSCs.

Efficient Sn–Pb Mixed Perovskite Solar Cells Via Minimizing Solvent Oxidation

AbstractTin (Sn)–lead (Pb) mixed perovskite solar cells (PSCs) stand out as the optimal choice for the bottom subcell of the all‐perovskite tandem solar cells. One of the major challenges impeding the further enhancement of Sn–Pb mixed PSCs power conversion efficiency (PCE) is the easy oxidation of Sn2+ to Sn4+ and a large number of Sn vacancies in the perovskite films. In this work, the sources of Sn2+ oxidation in the perovskite precursor solution are systematically investigated, focusing on the oxidation state of raw materials, solvent‐dissolved oxygen, and solvent oxidizing ability. It is discovered that compared to the commonly used dimethyl sulfoxide (DMSO) solvent, N, N'‐Dimethylpropyleneurea (DMPU) exhibits a weaker oxidizing ability while forming excellent coordination with the perovskite precursor. Using a mixed solvent of N, N‐Dimethylformamide (DMF), and DMPU as the precursor solvent not only obviates the need for additional antioxidants but also demonstrates reduced oxidation susceptibility toward Sn–Pb mixed perovskite. Utilizing a gas‐assisted technique without anti‐solvents, high‐efficiency Sn–Pb mixed PSCs are fabricated. These findings not only deepen the understanding of the oxidation phenomena in Sn–Pb perovskite precursor solutions but also provide essential guidance for the scalable production of Sn–Pb mixed PSCs and tandem solar cells.

Synergetic Near- and Far-Field Plasmonic Effects for Optimal All-Perovskite Tandem Solar Cells with Maximized Infrared Absorption.

The efficiency and reliability of perovskite solar cells have rapidly increased in conjunction with the proposition of advanced single-junction and multi-junction designs that allow light harvesting to be maximized. However, Sn-based compositions required for optimized all-perovskite tandem devices have reduced absorption coefficients, as opposed to pure Pb perovskites. To overcome this, we investigate near- and far-field plasmonic effects to locally enhance the light absorption of infrared photons. Through optimization of the metal type, particle size, and volume concentration, we maximize effective light harvesting while minimizing parasitic absorption in all-perovskite tandem devices. Interestingly, incorporating 240 nm silver particles into the Pb-Sn perovskite layer with a volume concentration of 3.1% indicates an absolute power conversion efficiency enhancement of 2% in the tandem system. We present a promising avenue for experimentalists to realize ultrathin all-perovskite tandem devices with optimized charge carrier collection, diminishing the weight and the use of Pb.

Reducing Hole Trap Density in Sn–Pb Perovskite Solar Cells via Molecular Phenylhydrazine

Narrow‐bandgap Sn–Pb‐alloyed perovskite is potential for a bottom cell in perovskite tandem solar cells. However, Sn‐contained perovskites tend to be readily oxidized in air atmosphere, which has ill influence on stability and photovoltaic performance. Herein, a method to suppress oxidation of divalent tin via post‐treatment of perovskite film with phenylhydrazine is reported. Phenylhydrazine‐treated FA0.5MA0.5Pb0.5Sn0.5I3 perovskite films effectively reduce the hole traps caused by the oxidation of Sn2+ on the perovskite surfaces. In addition, surface energetics are well aligned by post‐treatment, which is beneficial for voltage gain and charge transport. As a result, power conversion efficiency (PCE) is increased from 18.16% to 20.67% after post‐treatment due mainly to the significant improvement of open‐circuit voltage from 0.75 to 0.83 V. Furthermore, the device stability is improved, where 91.67% of initial PCE is maintained after 1000 h.

Indium Iodide Additive Realizing Efficient Mixed Sn─Pb Perovskite Solar Cells

AbstractLow‐bandgap mixed tin (Sn)‐lead (Pb) perovskite solar cells promise efficiency beyond the pure‐Pb ones. However, the difference in the interaction rate of SnI2 and PbI2 with organic salts causes spatial distribution heterogeneity of Sn2+ and Pb2+ in mixed Sn─Pb perovskite layers. This causes a Sn‐rich surface, which can trigger more severe Sn2+ oxidation and nonradiative recombination. A strategy, of introducing indium ion (In3+) into the perovskite precursor solution to compete with Sn2+ when reacting with organic salts is developed. Therefore, the nucleation and crystallization of perovskite films are well‐controlled, leading to improved film quality with a more balanced Sn/Pb ratio on the film surface. Additionally, In3+ has a lower reduction potential compared to Sn2+ which can generate an extra energy barrier for Sn2+ oxidation. The improved film quality and reduced surface oxidation result in accelerated electron transfer and reduced carrier recombination rate. The modified devices achieve a power conversion efficiency (PCE) of 23.34%, representing one of the highest PCEs in mixed Sn─Pb solar cells made with PCBM.

Substitution of lead with tin suppresses ionic transport in halide perovskite optoelectronics.

Despite the rapid rise in the performance of a variety of perovskite optoelectronic devices with vertical charge transport, the effects of ion migration remain a common and longstanding Achilles' heel limiting the long-term operational stability of lead halide perovskite devices. However, there is still limited understanding of the impact of tin (Sn) substitution on the ion dynamics of lead (Pb) halide perovskites. Here, we employ scan-rate-dependent current-voltage measurements on Pb and mixed Pb-Sn perovskite solar cells to show that short circuit current losses at lower scan rates, which can be traced to the presence of mobile ions, are present in both kinds of perovskites. To understand the kinetics of ion migration, we carry out scan-rate-dependent hysteresis analyses and temperature-dependent impedance spectroscopy measurements, which demonstrate suppressed ion migration in Pb-Sn devices compared to their Pb-only analogues. By linking these experimental observations to first-principles calculations on mixed Pb-Sn perovskites, we reveal the key role played by Sn vacancies in increasing the iodide ion migration barrier due to local structural distortions. These results highlight the beneficial effect of Sn substitution in mitigating undesirable ion migration in halide perovskites, with potential implications for future device development.

Self-assembly construction of a homojunction of Sn–Pb perovskite using an antioxidant for all-perovskite tandem solar cells with improved efficiency and stability

Self-assembly construction of a homojunction with antioxidant encapsulation for efficient and stable narrow bandgap perovskite solar cells and all-perovskite tandem solar cells.

Tin–lead halide perovskite solar cells with a robust hole transport layer

Cesium carbonate is used to modify the labile PEDOT : PSS into a robust polymer substrate, which suppresses nonradiative recombination and chemical erosion at the buried interface, enabling Sn–Pb perovskite solar cells with >23% efficiency.

Selection of phenyl hydrazine derivatives as an Sn4+ reductant for tin–lead perovskite solar cells

Proposed Sn–Pb perovskites: hydrochlorination suppresses phenyl hydrazine deprotonation, enhancing device stability, photovoltage, and efficiency at AM1.5 with sulfonamide.

Decoupling light- and oxygen-induced degradation mechanisms of Sn–Pb perovskites in all perovskite tandem solar cells

Decoupling light- and oxygen-induced degradation mechanisms of Sn–Pb perovskites in all perovskite tandem solar cells

Unprecedented inorganic HTL-based MA-free Sn–Pb perovskite photovoltaics with an efficiency over 23%

This study presents a highly efficient, stable MA-free Sn–Pb perovskite solar cell with a NiOx-based HTL and GeOx passivation.

Accelerated Redox Reactions Enable Stable Tin‐Lead Mixed Perovskite Solar Cells

AbstractThe facile oxidation of Sn2+ to Sn4+ poses an inherent challenge that limits the efficiency and stability of tin‐lead mixed (Sn−Pb) perovskite solar cells (PSCs) and all‐perovskite tandem devices. In this work, we discover the sustainable redox reactions enabling self‐healing Sn−Pb perovskites, where their intractable oxidation degradation can be recovered to their original state under light soaking. Quantitative and operando spectroscopies are used to investigate the redox chemistry, revealing that metallic Pb0 from the photolysis of perovskite reacts with Sn4+ to regenerate Pb2+ and Sn2+ spontaneously. Given the sluggish redox reaction kinetics, V3+/V2+ ionic pair is designed as an effective redox shuttle to accelerate the recovery of Sn−Pb perovskites from oxidation. The target Sn−Pb PSCs enabled by V3+/V2+ ionic pair deliver an improved power conversion efficiency (PCE) of 21.22 % and excellent device lifespan, retaining nearly 90 % of its initial PCE after maximum power point tracking under light for 1,000 hours.

Tuning Structure and Excitonic Properties of 2D Ruddlesden-Popper Germanium, Tin, and Lead Iodide Perovskites via Interplay between Cations.

The compositional tunability of 2D metal halide perovskites enables exploration of diverse semiconducting materials with different structural features. However, rationally tuning the 2D perovskite structures to target physical properties for specific applications remains challenging, especially for lead-free perovskites. Here, we study the effect of the interplay of the B-site (Ge, Sn, and Pb), A-site (cesium, methylammonium, and formamidinium), and spacer cations on the structure and optical properties of a new series of 2D Ruddlesden-Popper perovskites using the previously unreported spacer cation 4-bromo-2-fluorobenzylammonium (4Br2FBZ). We report eight new crystal structures and study the consequence of varying the B-site (Pb, Sn, Ge) and dimension (n = 1, 2, vs 3D). Dimension strongly influences local distortion and structural symmetry, and the increased octahedral tilting and lone pair effects in Ge perovskites lead to a polar n = 2 perovskite that exhibits second harmonic generation, (4Br2FBZ)2(Cs)Ge2I7. In contrast, the analogous Sn and Pb perovskites remain centrosymmetric, but the B-site metal influences the photoluminescence properties. The Pb perovskites exhibit broad, defect-mediated emission at low temperature, whereas the Sn perovskites show purely excitonic emission over the entire temperature range, but the carrier recombination dynamics depend on dimensionality and dark excitonic states. Wholistic understanding of these differences that arise based on cations and dimensionality can guide the rational materials design of 2D perovskites for targeting physical properties for optoelectronic applications based on the interplay of cations and the connectivity of the inorganic framework.

Assessing the impact of triaxial strain on carrier mobility and dielectric properties in cubic CsBCl3 (B = Pb, Sn, or Ge) perovskites: A first principles study

Investigating the strain and pressure dependence of perovskite materials can provide valuable insights into their structural and electronic responses, enabling the fine-tuning of their properties for various technological applications. This study investigates the influence of controlled lattice compression and expansion on the acoustic phonon-limited carrier mobility in CsBCl3 (B = Pb, Sn, Ge) perovskites, revealing tunable electronic bandgaps ranging from 0.3 to 1.2 eV by varying the B cation type and applied triaxial strain. The research demonstrates significant and monotonic carrier mobility modulation under pressure, with changes of up to 124% even at modest strain levels of −2%, along with linearly increasing exciton binding energy with lattice parameter expansion.

Biotoxicity of Halide Perovskites in Mice.

Halide perovskites are crystalline semiconductors with exceptional optoelectronic properties, rapidly developing toward large-scale applications. Lead (II) (Pb2+ ) is the core element used to prepare halide perovskites. Pb2+ can displace key 2+ elements, including calcium, zinc and iron, that regulate vital physiological functions. Sn2+ can replace Pb2+ within the perovskite structure and, if accidentally dispersed in the environment, it readily oxidizes to Sn4+ , which is compatible with physiological functions and thus potentially safe. The 3+ salt bismuth (III) (Bi3+ ) is also potentially safe for the same reason and useful to prepare double perovskites. Here, this work studies the biotoxicity of Pb, Sn, and Bi perovskites in mice for the first time. This work analyses histopathology and growth of mice directly exposed to perovskites and investigate the development of their offspring generation. This study provides the screening of organs and key physiological functions targeted by perovskite exposure to design specific studies in mammalians.