Low-dimensional Perovskites Research Articles

Ultrafast Antisolvent Growth of Single-Crystalline CsPbCl3 Microcavity for Low-Threshold Room Temperature Blue Lasing.

All-inorganic perovskite CsPbCl3 has recently attracted considerable attention due to its great potentials for the development of high-efficiency, deep-blue optoelectronic devices. Particularly, single-crystalline CsPbCl3 planar microstructures provide good platforms for both fundamental studies and nanophotonics applications from lasers and detectors to amplifiers. In this study, we report an ultrafast antisolvent deposition route to fabricate single-crystalline CsPbCl3 microplatelets (MPs). The as-grown MPs exhibit uniform morphology, strong emission, and outstanding gain property. Room temperature photoluminescence lasing is realized at 428 nm with a low threshold of 11.5 μJ cm-2 and high net optical gain up to 720 cm-1. These findings advance fundamental understanding on the fabrication and optoelectronic applications of low-dimensional CsPbCl3 perovskite structures.

Highly Orientational Order Perovskite Induced by In situ-generated 1D Perovskitoid for Efficient and Stable Printable Photovoltaics.

Employing low-dimensional perovskite has been proven to be a promising approach to enhance the efficiency and stability of perovskite solar cells. Here, thiopheniformamidine hydrochloride is introduced into CH3 NH3 PbI3 -based printable mesoscopic perovskite solar cells, to form 1D iodide lead thiophenamidine (TFPbI3 ) in situ. This judiciously designed low-dimensional perovskite can effectively passivate the defect of perovskite and induce the perovskite crystals to grow in a direction perpendicular to the substrate. Thus, the obtained 1D@3D perovskite could suppress the charge recombination and promote the charge transfer significantly. Benefiting from its dual effect and robustness, a significantly improved power conversion efficiency of 17.42% is yielded. The authors also develop high-performance printable mesoscopic perovskite solar cells with a champion efficiency approaching 13% for aperture area about 11.8 cm2 , as well as outstanding operational stability, retaining 90% of the original power conversion efficiency after 1000 hours of continuous illumination at the maximum power point in air.

Temperature‐Reliable Low‐Dimensional Perovskites Passivated Black‐Phase CsPbI3 toward Stable and Efficient Photovoltaics

Low-dimensional (LD) perovskites can effectively passivate and stabilize 3D perovskites for high-performance perovskite solar cells (PSCs). Regards CsPbI3 -based PSCs, the influence of high-temperature annealing on the LD perovskite passivation effect has to be taken into account due to fact the black-phase CsPbI3 crystallization requires high-temperature treatment, however, which has been rarely concerned so far. Here, the thermal stability of LD perovskites based on three hydrophobic organic ammonium salts and their passivation effect toward CsPbI3 and the whole device performance, have been investigated. It is found that, phenyltrimethylammonium iodide (PTAI) and its corresponding LD perovskites exhibit excellent thermal stability. Further investigation reveals that PTAI-based LD perovskites are mainly distributed at grain boundaries, which not only enhances the phase stability of CsPbI3 but also effectively suppresses non-radiative recombination. As a consequence, the champion PSC device based on CsPbI3 exhibits a record efficiency of 21.0 % with high stability.

From Bulk to Surface Passivation: Double Role of Chlorine‐Doping for Boosting Efficiency of FAPbI3‐rich Perovskite Solar Cells

Defect‐mediated recombination losses limit the open‐circuit voltage (VOC) of perovskite solar cells (PSCs), negatively affecting the device's performance. Bulk and dimensional engineering have both been reported as promising strategies to passivate shallow defects, thus improving the photovoltaic conversion efficiency (PCE). Here, a combined bulk and surface treatment employing chlorine‐based compounds is employed. Methylammonium chloride (MACl) is used as a bulk additive, while 4‐methylphenethylammonium chloride (MePEACl) is deposited onto the perovskite surface to produce a low‐dimensional perovskite (LDP) and reduce nonradiative recombination. Through structural and morphological investigations, it can be confirmed that bulk and surface doping have a beneficial effect on the film morphology and its overall quality, while electroluminescence (EL) and photoluminescence (PL) analyses demonstrate an increased and more homogeneous emission. Applying this double passivation strategy in PSC fabrication, a boost is observed in both the short‐circuit current density and the VOC of the devices, achieving a champion 21.4% PCE while improving device stability.

Chiral Ligand-Induced Structural Transformation of Low-Dimensional Hybrid Perovskite for Circularly Polarized Photodetection

Chiral Ligand-Induced Structural Transformation of Low-Dimensional Hybrid Perovskite for Circularly Polarized Photodetection

Pressure Tuning of Optical Properties and Structures in All-Inorganic Halide Perovskite Rb7Sb3Cl16.

All lead-free inorganic halide perovskites, as efficient solid-state light emission materials, have become ideal green optoelectronic materials to replace lead halide perovskites for diversified lighting and display applications with their excellent stability. Here, we investigated the pressure-derived optical and structural response of a zero-dimensional lead-free perovskite Rb7Sb3Cl16 through applying controllable pressure. A pressure-induced blue shift of the broadband emission was achieved, and it was followed by the emission color transformation from yellow to green, which was ascribed to the electron-phonon coupling weakening and the suppression of structural deformation upon lattice contraction. In parallel, the band gap was narrowed by about 0.5 eV as a result of enhanced metal halide orbital overlap under high pressure. This work provides a fundamental understanding for modulating the optical properties of the low-dimensional metal halide perovskites.

Uncovering synergistic effect of chloride additives for efficient quasi-2D perovskite solar cells

• MACl and PbCl 2 binary additives form MAPbCl 3 intermediate phase. • Perovskite crystallization is retarded and volatilization of MACl is prevented. • Such a synergistic effect leads to high-quality Q-2D perovskite films. • Charge recombination is suppressed and charge extraction efficiency is enhanced. • The champion PCE of 18.67% is one of the highest PCE for Q-2D RP PSCs with n ≤ 4. Methylammonium chloride (MACl) and lead chloride (PbCl 2 ) are commonly used for improving perovskite film quality. However, the rapid release of volatile MACl would lead to low-quality perovskite films with pinholes and defects. Here, we report a strategy of employing MACl&PbCl 2 binary additives together to prepare high-quality quasi-two-dimensional (Q-2D) Ruddlesden–Popper (RP) perovskite films. We found that MAPbCl 3 intermediate phase is formed via a reaction between MACl and PbCl 2 , which suppresses the fast volatilization of MACl, resulting in a compact and pinhole-free perovskite film with large grains. Moreover, the trap states are passivated via the incorporation of Cl – into the Q-2D perovskite crystals along with the addition of PbCl 2 , leading to a reduced charge recombination loss and an improved charge extraction. A remarkable power conversion efficiency (PCE) of 18.67% is achieved in such Q-2D RP PSCs, one of the highest PCE values among the low-dimensional RP PSCs with n ≤ 4. The environmental stability of the devices is also significantly enhanced. Our results provide an effective strategy by using chloride based additives for fabricating high-quality low-dimensional RP perovskite films for efficient solar cells.

Preparation of tin-based perovskite solar cell thin films assisted by stannous fluoride

While the conversion efficiency is constantly refreshing, perovskite solar cells are also actively moving towards the goal of commercial application. However, its structure contains Pb, a toxic substance, which violates the original intention of energy saving and environmental protection of solar cells and hinders the development of its commercialization. The purpose of this paper is to improve the device performance of environment-friendly lead-free tin-based perovskite solar cells. In this paper, SnF2 is firstly precipitated in perovskite solution and used as heterogeneous nucleation point, which helps tin-based perovskite precipitate faster and more uniformly, and then grows into a flat and compact film after annealing. With the increase of x, the lattice shrinkage of perovskite becomes more obvious, and the unit cell size of the film surface becomes larger. When x increases from 0 to 0.5, the energy conversion efficiency of the same batch of devices reaches 1.803% and VOC is 0.3283 V when x=0.5 is used. Low dimensional tin-based perovskite is formed by doping phenylethylamine into FASnI3 structure, and perovskite thin films are prepared by one-step method with different anti-solvent spin coating, which improves the device performance and greatly improves the stability of solar cells.

Non-selective adsorption of organic cations enables conformal surface capping of perovskite grains for stabilized photovoltaic operation

Chemical passivation of defective perovskite surface is a fundamental strategy to stabilize solar cell operation by impeding the defect-dominant surface ion migration. Here, we show that the configuration of organic cations plays a key role in determining their surface adsorption energetics at various perovskite facets, which will strongly impact the spatial uniformity of the low-dimensional perovskite passivation layer (LDPL). A weak-anisotropic adsorption behavior is demonstrated for tertiary ammonium that can enable a conformal LDPL on the perovskite grain surface. Benefiting from comprehensive surface passivation, the migration of ionic perovskite species was suppressed and the as-fabricated p-i-n solar cells yielded an optimized power conversion efficiency of 22.6% with an expected T 80 lifetime of about 4,000 h under continuous 1-sun illumination. Our findings give insight into the design and preparation of heterostructured perovskite films toward efficient and stable solar cells. • Surface adsorption enthalpy of organic cations is closely related to their configuration • Tertiary ammonium passivation results in conformally capped low-dimension perov. phase • Ion migration is suppressed in heterostructured perovskite film • The as-modified solar cells possess a stable efficiency under various stressors Taking advantage of the weak-anisotropic adsorption nature of tertiary ammonium on perovskite facets, Zhou et al. demonstrate a comprehensive protection of perovskite grain surface by constructing a conformal low-dimensional perovskite passivation layer. The inhibited ion migration enables stabilized solar cell operation.

Temperature-Responsive Photoluminescence and Elastic Properties of 1D Lead Halide Perovskites R- and S-(Methylbenzylamine)PbBr3.

Low-dimensional metal halide perovskites (MHPs) have received much attention due to their striking semiconducting properties tunable at a molecular level, which hold great potential in the development of next-generation optoelectronic devices. However, the insufficient understanding of their stimulus-responsiveness and elastic properties hinders future practical applications. Here, the thermally responsive emissions and elastic properties of one-dimensional lead halide perovskites R- and S-MBAPbBr3 (MBA+ = methylbenzylamine) were systematically investigated via temperature-dependent photoluminescence (PL) experiments and first-principles calculations. The PL peak positions of both perovskites were redshifted by about 20 nm, and the corresponding full width at half maximum was reduced by about 40 nm, from ambient temperature to about 150 K. This kind of temperature-responsive self-trapped exciton emission could be attributed to the synergistic effect of electron–phonon coupling and thermal expansion due to the alteration of hydrogen bonding. Moreover, the elastic properties of S-MBAPbBr3 were calculated using density functional theory, revealing that its Young’s and shear moduli are in the range of 6.5–33.2 and 2.8–19.5 GPa, respectively, even smaller than those of two-dimensional MHPs. Our work demonstrates that the temperature-responsive emissions and low elastic moduli of these 1D MHPs could find use in flexible devices.

Ion Migration in Organic-Inorganic Hybrid Perovskite Solar Cells: Current Understanding and Perspectives.

Organic-inorganic hybrid perovskite (OIHPs) solar cells are the most promising alternatives to traditional silicon solar cells, with a certified power conversion efficiency beyond 25%. However, the poor stability of OHIPs is one of the thorniest obstacles that hinder its commercial development. Among all the factors affecting stability, ion migration is prominent because it is unavoidable and intrinsic in OHIPs. Therefore, it is important to understand the mechanism for ion migration and regulation strategies. Herein, the types of ions that may migrate in OHIPs are first discussed; afterward, the migrating channels are demonstrated. The effects of ion migration are further elaborated. While ion migration can facilitate the p-i-n structure in some cases, the current hysteresis and other adverse effects such as phase segregation in OHIPs attract widespread attention. Based on these, several recent strategies to suppress the ion migration are enumerated, including the introduction of alkali cations, organic additives, grain boundaries passivation, and employment of low-dimensional perovskites. Finally, the prospect for further modulating the ion migration and more stable perovskite solar cells is proposed.

Fabrication of 2D perovskite (PMA)2PbI4 crystal and Cu ion implantation improved x-ray detector

Two-dimensional (2D) perovskites have been demonstrated great promise in x-ray detection application because of their stability, tunability, and the unique electronic properties. The centimeter-sized 2D perovskite (PMA)2PbI4 single crystal and the corresponding x-ray detector were fabricated. The Cu ion implanted device exhibits an excellent sensitivity of 283 μC Gyair−1 cm−2, the significantly enhanced mobility-lifetime (μτ) product of 8.05 × 10−3 cm2 V−1, and the lowest detectable dose rate of 2.13 μGyair s−1. Experimental observation combined with the DFT calculations shows that the improvement in Cu ion implanted x-ray detection is ascribed to the enhanced photoinduced charge carrier density and μτ product, and the increased carrier dissociation capability associated deeply with the decreased binding energy of exciton in the inorganic layer quasi-quantum well. The incorporation of the Cu interstitials by high-energy Cu ion implantation is able to introduce the donor and acceptor states with additional charge transfer channeling, resulting in the decreased exciton binding energy and fast dissociation of the exciton and the quick carrier extraction. Cu ion implantation regulating the dissociation of charge carriers in low-dimensional perovskites will motivate the application for 2D perovskite in high-performance x-ray detectors.

Ultrasensitive Near-Infrared Circularly Polarized Light Detection Using 3D Perovskite Embedded with Chiral Plasmonic Nanoparticles.

Chiral organic ligand‐incorporated low‐dimensional metal‐halide perovskites have received increasing attention for next‐generation photodetectors because of the direct detection capability of circularly polarized light (CPL), which overcomes the requirement for subsidiary optical components in conventional CPL photodetectors. However, most chiral perovskites have been based on low‐dimensional structures that confine chiroptical responses to the ultraviolet (UV) or short‐wavelength visible region and limit photocurrent due to their wide bandgap and poor charge transport. Here, chiroptical properties of 3D Cs0.05FA0.5MA0.45Pb0.5Sn0.5I3 polycrystalline films are achieved by incorporating chiral plasmonic gold nanoparticles (AuNPs) into the mixed Pb—Sn perovskite, without sacrificing its original optoelectronic properties. CPL detectors fabricated using chiral AuNP‐embedded perovskite films can operate without external power input; they exhibit remarkable chirality in the near‐infrared (NIR) region with a high anisotropy factor of responsivity (g res) of 0.55, via giant plasmon resonance shift of chiral plasmonic AuNPs. In addition, a CPL detector array fabricated on a plastic substrate demonstrates highly sensitive self‐powered NIR detection with superior flexibility and durability.

Dimensional Tailoring Endows Tin Halide Perovskite Solar Cells with High Efficiency and Stability

Tin halide perovskite solar cells (TPSCs) have been recognized as one of the most promising candidates for efficient and stable eco-friendly photovoltaic technology. The certified power conversion efficiency of TPSCs has been delivered to over 14% recently. Emerging low-dimensional tin halide perovskites such as Ruddlesden-Popper (RP), Dion−Jacobson (DJ), or 2D-3D perovskite structures have recently offered new approaches to stabilizing tin perovskite devices. Given the important role of low-dimensional tin perovskites, in this review, we focused on the dimensionality regulation in TPSCs to clarify the rule of performance and stability. We first discussed the structural flexibility and optoelectronic properties of tin halide perovskites. Moreover, the updated development along with the use of large organic spacer cations was assessed. Last, we reviewed the status of RP, DJ, 2D-3D mixed perovskites, and surface passivation strategy to boost the efficiency and operational stability of TPSCs, further highlighting the current challenges to enhancing these key performance metrics.

High piezoresponse in low-dimensional inorganic halide perovskite for mechanical energy harvesting

We synthesized 2D CsPb2Br5 layered perovskite which shows piezoelectric and ferroelectric properties at room temperature. Additionally, composites of CsPb2Br5 and PVDF were fabricated to examine energy harvesting behavior as a nanogenerator.

Near-room-temperature reversible switching of quadratic optical nonlinearities in a one-dimensional perovskite-like hybrid

The switching of quadratic nonlinear optical (NLO) effects between two or more NLO states of solid-state materials represents an intriguing new branch in the field of photoelectrics and optics. While structural phase transitions have shown potential in this field, near-room-temperature reversible NLO switches have rarely been reported. To exploit new NLO switching materials within the structurally flexible class of hybrid perovskites, here, we synthesize a one-dimensional perovskite-like hybrid, (MP)PbBr3 (where MP+ is a 1-methylpyrrolidinium cation), through a facile solution method, which exhibits strong second harmonic generation (SHG) activities with an intensity of ~1.6 times as large as potassium dihydrogen phosphate. Intriguingly, (MP)PbBr3 enables the near-room temperature reversible switching of SHG properties, showing a large NLO switching contrast of up to ~40 between its SHG-active and SHG-inactive phases, beyond most of its liquid counterparts. Further microscopic structural analyses reveal that the dynamic ordering of the organic MP+ cation and inorganic chain-like skeleton triggers its centrosymmetric (P63/mmc) to acentric (P212121) phase transition at 316 K upon cooling, resulting in a crucial contribution to its NLO switching properties. This work illustrates the potential of this material as a candidate for solid-state NLO switches and will promote the development of NLO materials within the family of low-dimensional hybrid perovskites.

Insight on noncovalent interactions and orbital constructs in low-dimensional antimony halide perovskites.

Reported is a series of eight antimony halide perovskite derivatives synthesized from acidic aqueous solutions of antimony oxide and halogen substituted pyridines. These materials feature anionic one-dimensional antimony halide (SbX; X = Cl, Br, I) chains or ribbons charge-balanced by organic para-halopyridinium cations (XPy; X = H, Cl, Br) which assemble into three-dimensional networks via halogen and hydrogen noncovalent interactions (NCIs) between ion pairs. Computational density functional theory (DFT) based natural bonding orbital (NBO) and density of state (DOS) methods were utilized to map the band structure and quantify and categorize noncovalent interaction strength and type. Moreover, we determined the presence of hybridized intermediate bands which are responsible for the small bandgap energies within this family and arise from mixing of the halide p-states and the Sb s-states. We note that the degree of hybridization, and thus optical properties, is influenced primarily by changes about inner sphere bonding and independent of second sphere interactions. This report is the first to specifically monitor the evolution of haloantimonate(III) hybrid perovskite atomic and molecular orbitals involved in optical behavior as a function of inner and outer sphere effects.

A first-principles study of exciton self-trapping and electric polarization in one-dimensional organic lead halide perovskites.

Revealing the origin of self-trapped excitons is a prerequisite for further improving the photoluminescence efficiency of low-dimensional organic perovskites. Here, the microscopic formation mechanism of intrinsic self-trapped excitons in one-dimensional (1D) C4N2H14PbX4 (X = Cl, Br and I) systems is investigated, and the polarization-luminescence relationship is established. Our results show that 1D-C4N2H14PbX4 has a low electronic dimension (flat band characteristics), which facilitates the formation of intrinsic self-trapped excitons. The potential well formed by local distortion of the [PbX6] octahedron is the origin of exciton self-trapping. Combined with the electronic density of states and partial charge density, we further confirmed the existence of intrinsic self-trapping excitons in 1D-C4N2H14PbX4. In addition, we found that the breaking of the central inversion symmetry will induce electric polarization, which greatly improves the transition probability of electrons. These results could potentially offer a new direction for improving the luminescence properties of 1D organic lead halide perovskites.

Multi‐Level Passivation of MAPbI3 Perovskite for Efficient and Stable Photovoltaics

AbstractThe photovoltaic performance and long‐term stability of perovskite solar cells (PSCs) are greatly affected by trap states. Herein, a functional ionic liquid of 1‐ethyl‐3‐methylimidazolium trifluoroacetate (EMIMTFA) is introduced, in which the 1‐ethyl‐3‐methylimidazolium cations (EMIM+) can interact with PbI2 to form a stable one‐dimensional (1D) perovskite of EMIMPbI3, and the trifluoroacetic acid anions (TFA−) can passivate the interface between the electron transfer layer and the perovskite layer. Unlike, the widely studied low dimensional perovskite capping layers or quasi‐2D configuration, the EMIM+ cations not only distribute on the top surface and inside the bulk phase, but also accumulate at the buried interface of 3D perovskite film, achieving a multi‐level distribution. The different defect states are successfully passivated by this distribution mode, leading to a significant decrease of non‐radiative recombination. As a result, the methyammonium lead iodide‐based PSCs with the EMIMTFA additive show an enhanced photovoltaic performance with a champion power conversion efficiency up to 22.14% and improved long‐term stability. This work demonstrates that the formation of multilevel low‐dimensional structure is a new strategy for the preparation of efficient and stable PSCs.

Femtosecond Exciton and Carrier Relaxation Dynamics of Two-Dimensional (2D) and Quasi-2D Tin Perovskites.

The dynamics of exciton and free-carrier relaxation of low-dimensional tin iodide perovskites, BA2FAn-1SnnI3n+1, where n = 1 (N1), 2 (N2), 5 (N5), and 10 (N10), were investigated with femtosecond transient absorption spectra (TAS). The absorption and photoluminescence spectra of N1 and N2 show exciton characteristics due to quantum confinement, whereas N5 and N10 display a free-carrier nature, the same as for bulk three-dimensional (3D) films. The TAS profiles were fitted according to a global kinetic model with three time coefficients representing the interactions of biexcitons, trions, and excitons for N1 and N2 and hot carriers, cold carriers, and shallow trap carriers for N5 and N10. The carrier relaxation dynamics of N5 and N10 were similar to those of 3D FASnI3 except for the absence of surface recombination in the deep-trap states due to passivation of the grain surfaces by the long alkyl chain for these quasi-2D samples (N5/N10 vs 3D).