Lead Isolation and Capture in Perovskite Photovoltaics toward Eco-Friendly Commercialization.

Perovskite solar cells (PSCs) are developed rapidly in efficiency and stability in recent years, which can compete with silicon solar cells. However, an important obstacle to the commercialization of PSCs is the toxicity of lead ions (Pb2+) from water-soluble perovskites. The entry of free Pb2+ into organisms can cause severe harm to humans, such as blood lead poisoning, organ failure, etc. Therefore, this work reports a "lead isolation-capture" dual detoxification strategy with calcium disodium edetate (EDTA Na-Ca), which can inhibit lead leakage from PSCs under extreme conditions. More importantly, leaked lead exists in a nontoxic aggregation state chelated by EDTA. For the first time, in vivo experiments are conducted in mice to systematically prove that this material has a significant inhibitory effect on the toxicity of perovskites. In addition, this strategy can further enhance device performance, enabling the optimized devices to achieve an impressive power conversion efficiency (PCE) of 25.19%. This innovative strategy is a major breakthrough in the research on the prevention of lead toxicity in PSCs.

Destabilization of Oxidized Lattice Oxygen in Layered Oxide Cathode.

Integrating anion-redox capacity with orthodox cation-redox capacity is deemed as a promising solution for high-energy-density battery cathodes surmounting the present technical bottlenecks. However, the evolution of oxidized oxygen species during the electrochemical or chemical process easily jeopardizes the reversibility of oxygen redox and remains poorly understood. Herein, we showcase the gradual conversion of the π-interacting oxygen (localized hole states on O) to the σ-interacting oxygen upon resting at a high voltage for P3-type Na0.6Li0.2Mn0.8O2 with nominally stable ribbon-like superstructure, accompanied by the O-O dimerization and the local structural reorganization. We further pinpoint an abnormal Li+ migration process from the alkali-metal layer to the transition-metal layer for desodiated P3-Na0.6Li0.2Mn0.8O2, thereby leading to a partial reconstruction of the ribbon superstructure. The high-voltage plateau of oxygen-redox cathodes is concluded to be exclusively controlled by the oxygen stabilization mechanism rather than the superstructure ordering. In addition, there exists a kinetic competition between π and σ interaction during the uninterrupted electrochemical process.

Efficient and Stable Inverted Perovskite Solar Modules Enabled by Solid-Liquid Two-Step Film Formation.

A considerable efficiency gap exists between large-area perovskite solar modules and small-area perovskite solar cells. The control of forming uniform and large-area film and perovskite crystallization is still the main obstacle restricting the efficiency of PSMs. In this work, we adopted a solid-liquid two-step film formation technique, which involved the evaporation of a lead iodide film and blade coating of an organic ammonium halide solution to prepare perovskite films. This method possesses the advantages of integrating vapor deposition and solution methods, which could apply to substrates with different roughness and avoid using toxic solvents to achieve a more uniform, large-area perovskite film. Furthermore, modification of the NiOx/perovskite buried interface and introduction of Urea additives were utilized to reduce interface recombination and regulate perovskite crystallization. As a result, a large-area perovskite film possessing larger grains, fewer pinholes, and reduced defects could be achieved. The inverted PSM with an active area of 61.56 cm2 (10 × 10 cm2 substrate) achieved a champion power conversion efficiency of 20.56% and significantly improved stability. This method suggests an innovative approach to resolving the uniformity issue associated with large-area film fabrication.

Surface heterojunction based on n-type low-dimensional perovskite film for highly efficient perovskite tandem solar cells.

Enhancing the quality of junctions is crucial for optimizing carrier extraction and suppressing recombination in semiconductor devices. In recent years, metal halide perovskite has emerged as the most promising next-generation material for optoelectronic devices. However, the construction of high-quality perovskite junctions, as well as characterization and understanding of their carrier polarity and density, remains a challenge. In this study, using combined electrical and spectroscopic characterization techniques, we investigate the doping characteristics of perovskite films by remote molecules, which is corroborated by our theoretical simulations indicating Schottky defects consisting of double ions as effective charge dopants. Through a post-treatment process involving a combination of biammonium and monoammonium molecules, we create a surface layer of n-type low-dimensional perovskite. This surface layer forms a heterojunction with the underlying 3D perovskite film, resulting in a favorable doping profile that enhances carrier extraction. The fabricated device exhibits an outstanding open-circuit voltage (VOC) up to 1.34 V and achieves a certified efficiency of 19.31% for single-junction wide-bandgap (1.77 eV) perovskite solar cells, together with significantly enhanced operational stability, thanks to the improved separation of carriers. Furthermore, we demonstrate the potential of this wide-bandgap device by achieving a certified efficiency of 27.04% and a VOC of 2.12 V in a perovskite/perovskite tandem solar cell configuration.

Charge Carrier Regulation for Efficient Blue Quantum-Dot Light-Emitting Diodes Via a High-Mobility Coplanar Cyclopentane[b]thiopyran Derivative.

The performance of blue quantum dot light-emitting diodes (QLEDs) is limited by unbalanced charge injection, resulting from insufficient holes caused by low mobility or significant energy barriers. Here, we introduce an angular-shaped heteroarene based on cyclopentane[b]thiopyran (C8-SS) to modify the hole transport layer poly-N-vinylcarbazole (PVK), in blue QLEDs. C8-SS exhibits high hole mobility and conductivity due to the π···π and S···π interactions. Introducing C8-SS to PVK significantly enhanced hole mobility, increasing it by 2 orders of magnitude from 2.44 × 10-6 to 1.73 × 10-4 cm2 V-1 s-1. Benefiting from high mobility and conductivity, PVK:C8-SS-based QLEDs exhibit a low turn-on voltage (Von) of 3.2 V. More importantly, the optimized QLEDs achieve a high peak power efficiency (PE) of 7.13 lm/W, which is 2.65 times that of the control QLEDs. The as-proposed interface engineering provides a novel and effective strategy for achieving high-performance blue QLEDs in low-energy consumption lighting applications.

Magnetic-biased chiral molecules enabling highly oriented photovoltaic perovskites.

The interaction between sites A, B and X with passivation molecules is restricted when the conventional passivation strategy is applied in perovskite (ABX3) photovoltaics. Fortunately, the revolving A-site presents an opportunity to strengthen this interaction by utilizing an external field. Herein, we propose a novel approach to achieving an ordered magnetic dipole moment, which is regulated by a magnetic field via the coupling effect between the chiral passivation molecule and the A-site (formamidine ion) in perovskites. This strategy can increase the molecular interaction energy by approximately four times and ensure a well-ordered molecular arrangement. The quality of the deposited perovskite film is significantly optimized with inhibited nonradiative recombination. It manages to reduce the open-circuit voltage loss of photovoltaic devices to 360 mV and increase the power conversion efficiency to 25.22%. This finding provides a new insight into the exploration of A-sites in perovskites and offers a novel route to improving the device performance of perovskite photovoltaics.

Electronically Manipulated Molecular Strategy Enabling Highly Efficient Tin Perovskite Photovoltaics.

Buried interface modification can effectively improve the compatibility between interfaces. Given the distinct interface selections in perovskite solar cells (PSCs), the applicability of a singular modification material remains limited. Consequently, in response to this challenge, we devised a tailored molecular strategy based on the electronic effects of specific functional groups. Therefore, we prepared three distinct silane coupling agents, and due to the varying inductive effects of these functional groups, the electronic distribution and molecular dipole moments of the coupling agents are correspondingly altered. Among them, trimethoxy (3,3,3-trifluoropropyl)-silane (F3 -TMOS), which possesses electron-withdrawing groups, generates a molecular dipole moment directed toward the hole transport layer (HTL). This approach changes the work function of the HTL, optimizes the energy level alignment, reduces the open-circuit voltage loss, and facilitates carrier transport. Furthermore, through the buffering effect of the coupling agent, the interface strain and lattice distortion caused by annealing the perovskite are reduced, enhancing the stability of the tin-based perovskite. Encouragingly, tin PSCs treated with F3 -TMOS achieved a champion efficiency of 14.67 %. This strategy provides an expedient avenue for the design of buried interface modification materials, enabling precise molecular adjustments in accordance with distinct interfacial contexts to ameliorate mismatched energetics and enhance carrier dynamics.

Regulating Perovskite Crystallization through Interfacial Engineering Using a Zwitterionic Additive Potassium Sulfamate for Efficient Pure-Blue Light-Emitting Diodes.

Quasi-two-dimensional (quasi-2D) perovskites are emerging as efficient emitters in blue perovskite light-emitting diodes (PeLEDs), while the imbalanced crystallization of the halide-mixed system limits further improvements in device performance. The rapid crystallization caused by Cl doping produces massive defects at the interface, leading to aggravated non-radiative recombination. Meanwhile, unmanageable perovskite crystallization is prone to facilitate the formation of nonuniform low-dimensional phases, which results in energy loss during the exciton transfer process. Here, we propose a multifunctional interface engineering for nucleation and phase regulation by incorporating the zwitterionic additive potassium sulfamate into the hole transport layer. By using potassium ions (K+ ) as heterogeneous nucleation seeds, finely controlled growth of interfacial K+ -guided grains is achieved. The sulfamate ions can simultaneously regulate the phase distribution and passivate defects through coordination interactions with undercoordinated lead atoms. Consequently, such synergistic effect constructs quasi-2D blue perovskite films with smooth energy landscape and reduced trap states, leading to pure-blue PeLEDs with a maximum external quantum efficiency (EQE) of 17.32 %, spectrally stable emission at 478 nm and the prolonged operational lifetime. This work provides a unique guide to comprehensively regulate the halide-mixed blue perovskite crystallization by manipulating the characteristics of grain-growth substrate.

Top-Down Exfoliation Process Constructing 2D/3D Heterojunction toward Ultrapure Blue Perovskite Light-Emitting Diodes.

3D perovskites with low energy disorder and high ambipolar charge mobility represent a promising solution for efficient and bright light-emitting diodes. However, the challenges of regulating the nanocrystal size to trigger the quantum confinement effect and control the surface trap states to reduce charge loss hinder the applications of 3D perovskites in blue perovskite light-emitting diodes (PeLEDs). In this study, we present a top-down exfoliation method to obtain blue 3D perovskite films with clipped nanocrystals and tunable bandgaps by employing methyl cyanide (MeCN) for post-treatment. In this method, the MeCN solvent exfoliates the surface components of the 3D perovskite grains through a partial dissolution process. Moreover, the dissolved precursor can be further utilized to construct an ingenious 2D/3D heterostructure by incorporating an organic spacer into the MeCN solvent, contributing to efficient defect passivation and improved energy transfer. Consequently, efficient PeLEDs featuring ultrapure blue emission at 478 nm achieve a record external quantum efficiency of 12.3% among their 3D counterparts. This work emphasizes the significance of inducing the quantum confinement effect in 3D perovskites for efficient blue PeLEDs and provides a viable scheme for the in situ regulation of perovskite crystals.

Anchoring Charge Selective Self-Assembled Monolayers for Tin-Lead Perovskite Solar Cells.

Self-assembled monolayers (SAMs) have displayed great potential for improving efficiency and stability in p-i-n perovskite solar cells (PSCs). The anchoring of SAMs at the conductiv metal oxide substrates and their interaction with perovskite materials must be rationally tailored to ensure efficient charge carrier extraction and improved quality of the perovskite films. Herein, SAMs molecules with different anchoring groups and spacers to control the interaction with perovskite in the p-i-n mixed Sn-Pb PSCs are selected. It is found that the monolayer with the carboxylate group exhibits appropriate interaction and has a more favorable orientation and arrangement than that of the phosphate group. This results in reduced nonradiative recombination and enhanced crystallinity. In addition, the short chain length leads to an improved energy level alignment of SAMs with perovskite, improving hole extraction. As a result, the narrow bandgap (≈1.25 eV) Sn-Pb PSCs show efficiencies of up to 23.1% with an open-circuit voltage of up to 0.89 V. Unencapsulated devices retain 93% of their initial efficiency after storage in N2 atmosphere for over 2500 h. Overall, this work highlights the underexplored potential of SAMs for perovskite photovoltaics and provides essential findings on the influence of their structural modification.

High-Stable Lead-Free Solar Cells Achieved by Surface Reconstruction of Quasi-2D Tin-Based Perovskites.

Tin halide perovskites are an appealing alternative to lead perovskites. However, owing to the lower redox potential of Sn(II)/Sn(IV), particularly under the presence of oxygen and water, the accumulation of Sn(IV) at the surface layer will negatively impact the device's performance and stability. To this end, this work has introduced a novel multifunctional molecule, 1,4-phenyldimethylammonium dibromide diamine (phDMADBr), to form a protective layer on the surface of Sn-based perovskite films. Strong interactions between phDMADBr and the perovskite surface improve electron transfer, passivating uncoordinated Sn(II), and fortify against water and oxygen. In situ grazing incidence wide-angle X-ray scattering (GIWAXS) analysis confirms the enhanced thermal stability of the quasi-2D phase, and hence the overall enhanced stability of the perovskite. Long-term stability in devices is achieved, retaining over 90% of the original efficiency for more than 200 hours in a 10% RH moisture N2 environment. These findings propose a new approach to enhance the operational stability of Sn-based perovskite devices, offering a strategy in advancing lead-free optoelectronic applications.

Phase-Pure α-FAPbI3 Perovskite Solar Cells via Activating Lead-Iodine Frameworks.

Narrow bandgap cubic formamidine perovskite (α-FAPbI3) is widely studied for its potential to achieve record­breaking efficiency. However, its high preparation difficulty caused by lattice instability is criticized. A popular strategy for stabilizing the α-FAPbI3 lattice is to replace intrinsic FA+ or I- with smaller ions of MA+, Cs+, Rb+, and Br-, whereas this generally leads to broadened optical bandgap and phase separation. Studies show that ions substitution-free phase-pure α-FAPbI3 can achieve intrinsic phase stability. However, the challenging preparation of high-quality films has hindered its further development. Here, a facile synthesis of high-quality MA+, Cs+, Rb+, and Br--free phase-pure α-FAPbI3 perovskite film by a new solution modification strategy is reported. This enables the activation of lead-iodine (Pb─I) frameworks by forming the coated Pb⋯O network, thus simultaneously promoting spontaneous homogeneous nucleation and rapid phase transition from δ to α phase. As a result, the efficient and stable phase-pure α-FAPbI3 PSC is obtained through a one-step method without antisolvent treatment, with a record efficiency of 23.15% and excellent long-term operating stability for 500 h under continuous light stress.

Nonvolatile Memory Organic Light-Emitting Transistors.

In the field of active-matrix organic light emitting display (AMOLED), large-size and ultra-high-definition AMOLED applications have escalated the demand for the integration density of driver chips. However, as Moore's Law approaches the limit, the traditional technology of improving integration density that relies on scaling down device dimension is facing a huge challenge. Thus, developing a multifunctional and highly integrated device is a promising route for improving the integration density of pixel circuits. Here, a novel nonvolatile memory ferroelectric organic light-emitting transistor (Fe-OLET) device which integrates the switching capability, light-emitting capability and nonvolatile memory function into a single device is reported. The nonvolatile memory function of Fe-OLET is achieved through the remnant polarization property of ferroelectric polymer, enabling the device to maintain light emission at zero gate bias. The reliable nonvolatile memory operations are also demonstrated. The proof-of-concept device optimized through interfacial modification approach exhibits 20 times improved field-effect mobility and five times increased luminance. The integration of nonvolatile memory, switching and light-emitting capabilities within Fe-OLET provides a promising internal-storage-driving paradigm, thus creating a new pathway for deploying storage capacitor-free circuitry to improve the pixel aperture ratio and the integration density of circuits toward the on-chip advanced display applications.

Highly Stable and Efficient Formamidinium-Based 2D Ruddlesden-Popper Perovskite Solar Cells via Lattice Manipulation.

Formamidinium (FA)-based 2D perovskites have emerged as highly promising candidates in solar cells. However, the insertion of 2D spacer cations into the perovskite lattice concomitantly introduces microstrain and unfavorable orientations that hinder efficiency and stability. In this study, by finely tuning the FA-based 2D perovskite lattice through spacer cation engineering, a stable lattice structure with balanced distortion, microstrain relaxation, and reduced carrier-lattice interactions is achieved. These advancements effectively stabilize the inherently soft lattice against light and thermal-aging stress. To reduce the photocurrent loss induced by undesired crystal texture, a polarity-matched molecular-type selenourea (SENA) additive is further employed to modulate the crystallization kinetics. The introduction of the SENA significantly inhibits the disordered crystallization induced by spacer cations and drives the templated growth of the quantum well structure with a vertical orientation. This controlled crystallization process effectively reduces crystal defects and enhances charge separation. Ultimately, the optimized FA-based perovskite photovoltaic devices achieve a remarkable power conversion efficiency (PCE) of 20.03% (certified steady-state efficiency of 19.30%), setting a new record for low-n 2D perovskite solar cells. Furthermore, the devices exhibit less than 1% efficiency degradation after operating at maximum power point for 1000 h and maintain excellent stability after thermal aging and cycles of cold-warm shock, respectively.

In Situ and Operando Characterization Techniques in Stability Study of Perovskite-Based Devices.

Metal halide perovskite materials have demonstrated significant potential in various optoelectronic applications, such as photovoltaics, light emitting diodes, photodetectors, and lasers. However, the stability issues of perovskite materials continue to impede their widespread use. Many studies have attempted to understand the complex degradation mechanism and dynamics of these materials. Among them, in situ and/or operando approaches have provided remarkable insights into the degradation process by enabling precise control of degradation parameters and real-time monitoring. In this review, we focus on these studies utilizing in situ and operando approaches and demonstrate how these techniques have contributed to reveal degradation details, including structural, compositional, morphological, and other changes. We explore why these two approaches are necessary in the study of perovskite degradation and how they can be achieved by upgrading the corresponding ex situ techniques. With recent stability improvements of halide perovskite using various methods (compositional engineering, surface engineering, and structural engineering), the degradation of halide perovskite materials is greatly retarded. However, these improvements may turn into new challenges during the investigation into the retarded degradation process. Therefore, we also highlight the importance of enhancing the sensitivity and probing range of current in situ and operando approaches to address this issue. Finally, we identify the challenges and future directions of in situ and operando approaches in the stability research of halide perovskites. We believe that the advancement of in situ and operando techniques will be crucial in supporting the journey toward enhanced perovskite stability.

Ion-Dipole Interaction Enabling Highly Efficient CsPbI3 Perovskite Indoor Photovoltaics.

Metal halide perovskites are ideal candidates for indoor photovoltaics (IPVs) because of their easy-to-adjust bandgaps, which can be designed to cover the spectrum of any artificial light source. However, the serious non-radiative carrier recombination under low light illumination restrains the application of perovskite-based IPVs (PIPVs). Herein, polar molecules of amino naphthalene sulfonates are employed to functionalize the TiO2 substrate, anchoring the CsPbI3 perovskite crystal grains with a strong ion-dipole interaction between the molecule-level polar interlayer and the ionic perovskite film. The resulting high-quality CsPbI3 films with the merit of defect-immunity and large shunt resistance under low light conditions enable the corresponding PIPVs with an indoor power conversion efficiency of up to 41.2% (Pin : 334.11 µW cm-2 , Pout : 137.66 µW cm-2 ) under illumination from a commonly used indoor light-emitting diode light source (2956 K, 1062 lux). Furthermore, the device also achieves efficiencies of 29.45% (Pout : 9.80 µW cm-2 ) and 32.54% (Pout : 54.34 µW cm-2 ) at 106 (Pin : 33.84 µW cm-2 ) and 522 lux (Pin : 168.21 µW cm-2 ), respectively.

Stable Electron-Transport-Layer-Free Perovskite Solar Cells with over 22% Power Conversion Efficiency.

Due to their low cost and simplified production process, electron-transport-layer-free (ETL-free) perovskite solar cells (PSCs) have attracted great attention recently. However, the performance of ETL-free PSCs is still at a disadvantage compared to cells with a conventional n-i-p structure due to the severe recombination of charge carriers at the perovskite/anode interface. Here, we report a strategy to fabricate stable ETL-free FAPbI3 PSCs by in situ formation of a low dimensional perovskite layer between the FTO and the perovskite. This interlayer gives rise to the energy band bending and reduced defect density in the perovskite film and indirect contact and improved energy level alignment between the anode and perovskite, which facilitates charge carrier transport and collection and suppresses charge carrier recombination. As a result, ETL-free PSCs with a power conversion efficiency (PCE) exceeding 22% are achieved under ambient conditions.

Perylene Monoimide Phosphorus Salt Interfacial Modified Crystallization for Highly Efficient and Stable Perovskite Solar Cells.

Reducing the interfacial defects of perovskite films is key to improving the performance of perovskite solar cells (PSCs). In this study, two kinds of perylene monoimide (PMI) derivative phosphonium bromide salts were designed and used as a multifunctional interface-modified layer in PSCs. These two molecules are inserted between SnO2 and perovskite to produce a bidirectional passivation effect. The interaction with SnO2 reduces the oxygen vacancy on the surface of SnO2 and tunes the energy level of the electron transport layer, making more matches with the perovskite layer. The modified layer can promote the growth of perovskite crystals and reduce the interfacial defects of the perovskite film. Furthermore, the power conversion efficiency (PCE) of PSCs increased from 19.49 to 22.85%, and the open-circuit voltage (VOC) increased from 1.06 to 1.14 V. At the same time, the PCE of the SnO2/PMI-TPP-based device remained 88% of the initial PCE after 240 h of continuous illumination. In addition, these two PMI derivatives with a quasi-planar structure can improve the flexibility of flexible PSCs. This study provided a new strategy for the interfacial modification of PSCs and a new insight into the application of flexible PSCs.

Highly efficient p-i-n perovskite solar cells that endure temperature variations.

Daily temperature variations induce phase transitions and lattice strains in halide perovskites, challenging their stability in solar cells. We stabilized the perovskite black phase and improved solar cell performance using the ordered dipolar structure of ß-poly(1,1-difluoroethylene) to control perovskite film crystallization and energy alignment. We demonstrated p-i-n perovskite solar cells with a record power conversion efficiency of 24.6% over 18 square millimeters and 23.1% over 1 square centimeter, which retained 96 and 88% of the efficiency after 1000 hours of 1-sun maximum power point tracking at 25° and 75°C, respectively. Devices under rapid thermal cycling between -60° and +80°C showed no sign of fatigue, demonstrating the impact of the ordered dipolar structure on the operational stability of perovskite solar cells.