Light-Triggered Sustainable Defect-Passivation for Stable Perovskite Photovoltaics

Photochemical Shield Enabling Highly Efficient Perovskite Photovoltaics

Oxygen is difficult to be physically removed. Oxygen will be excited by light to form free radicals which further attack the lattice of perovskite. The stabilization of α-FAPbI3 against δ-FAPbI3 is the key to optimize perovskite solar cells. Herein, the simple molecule, benzaldehyde (BAH) is adopted. The photochemical shield will be established in perovskite layer. Moreover, heterogeneous nucleation induced by BAH enhances the crystallization of α-FAPbI3. Consequently, the stability of device is improved significantly. The target device maintains 95% of original power conversion efficiency after 1500 h under air conditions and light-emitting diode light. The power conversion efficiency increases from 23.21% of pristine device to 24.82% of target device.

Mechanical Durability and Flexibility in Perovskite Photovoltaics: Advancements and Applications

The remarkable progress in perovskite solar cell (PSC) technology has witnessed a remarkable leap in efficiency within the past decade. As this technology continues to mature, flexible PSCs (F-PSCs) are emerging as pivotal components for a wide array of applications, spanning from powering portable electronics and wearable devices to integrating seamlessly into electronic textiles and large-scale industrial roofing. F-PSCs characterized by their lightweight, mechanical flexibility, and adaptability for cost-effective roll-to-roll manufacturing, hold immense commercial potential. However, the persistent concerns regarding the overall stability and mechanical robustness of these devices loom large. This comprehensive review delves into recent strides made in enhancing the mechanical stability of F-PSCs. It covers a spectrum of crucial aspects, encompassing perovskite material optimization, precise crystal grain regulation, film quality enhancement, strategic interface engineering, innovational developed flexible transparent electrodes, judicious substrate selection, and the integration of various functional layers. By collating and analyzing these dedicated research endeavors, this review illuminates the current landscape of progress in addressing the challenges surrounding mechanical stability. Furthermore, it provides valuable insights into the persistent obstacles and bottlenecks that demand attention and innovative solutions in the field of F-PSCs.

Enhancing Ultraviolet Stability and Performance of Wide Bandgap Perovskite Solar Cells Through Ultraviolet Light-Absorbing Passivator

Ultraviolet light (UV) has caused tremendous damage to perovskite solar cells (PSCs), degrading the perovskite and shortening their lifetime. Defects act as non-radiative recombination sites, accelerate the degradation process, reduce the efficiency of the device and weaken the stability of solar cell. In this work, to realize efficient and stable p-i-n wide bandgap solar cells under UV, a synergetic strategy utilizing UV light-absorbing passivator, (Trifluoroacetyl) benzotriazole (TFABI), enhance UV photostability and regulate the defect passivation is proposed. By using TFABI, the degradation of the perovskite absorption layer under UV light is suppressed, spectral response is enhanced and the Pb vacancy defects are passivated. As a result, the target device achieves an efficiency of 21.54%, exhibiting excellent long-term stability under 365 nm UV irradiation. After 60 h of irradiation, it retains 85% of its initial value (60 mW cm-2 , RH 25-30%, 25 °C).

Self-Healing Behavior of the Metal Halide Perovskites and Photovoltaics

Perovskite solar cells have achieved rapid progress in the new-generation photovoltaic field, but the commercialization lags behind owing to the device stability issue under operational conditions. Ultimately, the instability issue is attributed to the soft lattice of ionic perovskite crystal. In brief, metal halide perovskite materials are susceptible to structural instability processes, including phase segregation, component loss, lattice distortion, and fatigue failure under harsh external stimuli such as high humidity, strong irradiation, wide thermal cycles, and large stress. Developing self-healing perovskites to further improve the unsatisfactory operational stability of their photoelectric devices under harsh stimuli has become a cutting-edge hotspot in this field. This self-healing behavior needs to be studied more comprehensively. Therefore, the self-healing behavior of the metal halide perovskites and photovoltaics is classified and summarized in this review. By discussing recent advances, underlying mechanisms, strategies, and existing challenges, this review provides perspectives on self-healing of perovskite solar cells in the future.

Molecular modification of MAPbI3 surface: insights from first-principles theory studies

Molecular surface modification has been widely used to improve the stability and the power conversion efficiency of perovskite solar cells. First-principles studies have played a crucial role in the mechanism of surface modification. However, the design of surface modification molecules lacks theoretical guidelines. Herein, we studied the surface modifications of a series of typical small molecules based on first-principles calculations. The relevance of the calculated properties and experimental performance has been investigated. It was found that molecules with nitrogen-containing groups, including amino, π-conjugated N-heterocycle, and (thio)amide groups, could have strong adsorption energies, and may be suitable modifiers. Molecules such as oxygen-containing six-membered rings and 1,2,4-triazine may induce defect states. Based on our calculations, design guidelines for perovskite surface modification molecules have been proposed based on three aspects: interfacial buffering, defect avoidance, and energy level alignment. This work may shed light on the development of perovskite surface modification molecules towards higher power conversion efficiency and more stable perovskite solar cells.

Tailoring passivators for highly efficient and stable perovskite solar cells

There is an ongoing global effort to advance emerging perovskite solar cells (PSCs), and many of these endeavours are focused on developing new compositions, processing methods and passivation strategies. In particular, the use of passivators to reduce the defects in perovskite materials has been demonstrated to be an effective approach for enhancing the photovoltaic performance and long-term stability of PSCs. Organic passivators have received increasing attention since the late 2010s as their structures and properties can readily be modified. First, this Review discusses the main types of defect in perovskite materials and reviews their properties. We examine the deleterious impact of defects on device efficiency and stability and highlight how defects facilitate extrinsic degradation pathways. Second, the proven use of different passivator designs to mitigate these negative effects is discussed, and possible defect passivation mechanisms are presented. Finally, we propose four specific directions for future research, which, in our opinion, will be crucial for unlocking the full potential of PSCs using the concept of defect passivation.

Anti-corrosion strategy to improve the stability of perovskite solar cells

In recent years, perovskite solar cells (PSCs) have been considered as one of the most promising photovoltaic technologies due to their solution processing, cost effectiveness, and excellent performance. The highest certified power conversion efficiency (PCE) achieved to date is 25.8%, which is approaching the best PCE of 26.81% achieved for silicon-based cells. However, perovskite materials are susceptible to various aging stressors, such as humidity, oxygen, temperature, and electrical bias, which hinder the industrialization of perovskite photovoltaic technologies. In this review, we discuss the lifetime of PSCs from the perspective of corrosion science. On one hand, benefiting from a series of anti-corrosion strategies (passivation, surface coating, machining etc.) used in corrosion science, the stability of perovskite devices is remarkably enhanced; on the other hand, given that perovskites are soft crystal lattices, which are different from traditional metals, the revealed degradation processes and specific methods to improve device operation stability can be applied to the field of corrosion, which can enrich and expand corrosion science.

Iodide/triiodide redox shuttle-based additives for high-performance perovskite solar cells by simultaneously passivating the cation and anion defects

Halide perovskite solar cells (PSCs) have received remarkably increasing interests due to their facile fabrication procedures, use of cost-effective raw materials, and high power conversion efficiencies (PCEs) during the past 10 years. Nevertheless, the state-of-the-art organic-inorganic PSCs suffer from high defect concentration and inferior humid/thermal stability, significantly restricting the widespread applications of PSCs. More specifically, point defects including metallic lead (Pb⁰) and halide iodine (I⁰) are easily generated in Pb/I-based PSCs during fabrication processes and operational conditions due to the inferior interaction between the anions and cations in halide perovskites and promote detrimental carrier recombination and ion migration, leading to inferior PCEs and durability of the PSCs. Herein, to tackle the above-mentioned issues, iodide/triiodide (I^-/I₃^-) redox shuttles as a new additive were introduced to simultaneously passivate the cation and anion defects of methylammonium lead iodide (MAPbI₃)-based PSCs. In particular, I^-/I₃^- redox shuttles play a vital role in regenerating the cation (Pb⁰) and anion (I⁰) defects through the redox cycles of Pb⁰/Pb²⁺ and I⁰/I^-. Consequently, the cell with an optimized amount of I^-/I₃^- additive generated a superior PCE of 20.4%, which was 12% higher than the pristine device (18.2%). Furthermore, the introduction of the I^-/I₃^- additive remarkably improved the humid and thermal stability of MAPbI₃-based PSCs. This work manifests the importance of the design of redox shuttle-based additives to boost the efficiency and durability of organic-inorganic PSCs.