Antiseptic Povidone-Iodine Heals the Grain Boundary of Perovskite Solar Cells

In Situ Film Stress Measurements Capture Increased Photostability in Additive-Engineered Mixed-Halide Perovskites

Mixed-halide perovskites segregate into iodide- and bromide-rich phases under light and have limited long-term reliability. We report for the first time on mechanical instability originating from illumination, which is monitored through thin-film stress measurements, both ex situ and in situ. We show that low-cost polymer additives, namely, corn starch and polyvinylpyrrolidone, not only induce a desirable compressive intrinsic stress in the thin film but also suppress the photoactivated phenomenon. The additives show no significant changes in stress and photoluminescence (PL) responses when the perovskite films are illuminated under ambient conditions. The controlled real-time in situ monitoring of the relative changes in stress quantifies mechanical durability under 1 sun illumination cycles. We therefore demonstrate a facile route to a photostable mixed-halide perovskite thin film using a scalable deposition technique with a quench-free processing route using nontoxic additives.

A Decade of Lead Halide Perovskites for Direct-Conversion X-ray and Gamma Detection: Technology Readiness Level and Challenges

Over the past decade, lead halide perovskites (LHPs) have become a vibrant thrust in the field of direct conversion X-ray and gamma-ray radiation detectors, offering promising cost-effective and robust alternatives to traditional semiconductors. This review article chronicles the significant strides made since the inception of this field, emphasizing the material, structural, and functional advancements. It begins with an overview of the fundamental properties of perovskites that render them suitable for high-energy radiation detection, such as their high atomic number, prominent charge carriers' mobility and lifetime, and high resistivity. The review highlights key developments in material synthesis and processing techniques that have enhanced these detectors' stability, efficiency, and scalability. Furthermore, the review discusses the evolution of device architectures from single-channel photodiodes to complex multi-pixel arrays for imaging applications. The conclusion is focused on the remaining challenges that hamper the immediate progression of LHP radiation detectors to higher technology levels. This review is intended as a resource for academic researchers and industry stakeholders, summarizing the first decade of LHP detectors and forecasting the trajectory of this promising field, while remembering that forecasting the future trajectory, though challenging, is guided by current technological trends.

Injectable iodine-containing peptide hydrogel for treatment of MRSA infection

Iodine is widely acknowledged for its potent antimicrobial properties. However, its clinical utility is often hampered by its unsatisfactory stability, uncontrolled release of active iodine and toxicity in moist environments. In this study, we report a novel iodine-containing hydrogel (I2@Nap-FFGP) designed for sustained iodine delivery under humid physiological and pathological conditions. I2@Nap-FFGP was fabricated using a self-assembling peptide-based hydrogel containing a proline motif to form a stable iodine complex. The resulting hydrogel exhibited excellent biocompatibility and robust antibacterial effect, it significantly inhibited bacteria-associated endometrial infections in mice and effectively alleviated inflammation. Moreover, the hydrogel successfully restored endometrial architecture and function. Notably, I2@Nap-FFGP remarkably improved pregnancy rates in mice with endometritis owing to its therapeutic effects. Our findings highlight the potential of this innovative hydrogel system for stable iodine application under humid and aqueous physiological conditions, offering a promising platform for future antibacterial therapies in clinical settings.

High-Quality Subsurface Construction of Perovskite Film for Efficient and Stable Solar Cells

The subsurface of perovskite (PVK) triggers non-radiative recombination and initiates film degradation due to the impurities and defects. This study investigates the limitations of the conventional surface post-treatment and proposes an innovative pre-treatment strategy to achieve complete impurity elimination and defect passivation of the subsurface. The considerable activity of unannealed PVK films provides a sufficient basis for effective subsurface modification. Following the pre-treatment, the cadmium ions (Cd2+) can occupy the lead (Pb) vacancies or substitute lead ions(Pb2+), while the introduced ionic ions (I-) are able to fill the ionic (I) vacancies. The stronger ionic bond between Cd2+ and I- helps prevent the loss of I-, leading to a reduction of defects in film, inhibiting non-radiative recombination and ionic migration at the interface. This innovative strategy successfully eliminates impurities and passivates defects, resulting in a perovskite subsurface characterized by high crystallinity, low defect density, and minimal impurity. These enhancements contribute to enhanced open circuit voltage (VOC)and fill factor (FF), leading to an impressive power conversion efficiency (PCE) of 24.49%. Notably, after 1600 h of aging in ambient air, the cell retained 87% of its initial performance.

Enhancing perovskite solar cell performance through PbI2 in situ passivation using a one-step process: experimental insights and simulations

The in situ passivation of a methylammonium lead triiodide (MAPbI3) phase spin-coated via a one-step process was experimentally investigated to elucidate their fundamental properties. Structural analysis revealed that MAPbI3 adopts a tetragonal crystal structure with a small excess of PbI2 (0.03 M) segregating at grain boundaries. Optical characterization indicated a band gap of 1.53 eV, highlighting the material's potential as an effective visible light absorber. To facilitate the fabrication of efficient perovskite solar cells (PSCs), we employed a primary n-i-p planar structure (ITO/SnO2/MAPbI3/spiro-OMeTAD/Au) in drift-diffusion SCAPS-1D simulations using experimental data from MAPbI3 layers containing excess PbI2. The simulations predicted a high power conversion efficiency (PCE) of approximately 24%. We further analyzed the impact of series resistance, shunt resistance, MAPbI3 thickness, defect density, as well as radiative and Auger recombination on photovoltaic performance, aiming to identify optimal parameters for enhanced device efficiency. Additionally, the use of ohmic contacts with AZO and IZO as the front and rear contacts, respectively, in the optimized device structure (AZO/SnO2/MAPbI3/spiro-OMeTAD/IZO) resulted in a PCE of 26.03%. These findings provide valuable insights for future research aimed at achieving high-efficiency bifacial MAPbI3 perovskite solar cells.

New Insights into MAI Additives in 2D-Assisted 3D Controlled Crystallization Toward High-Quality α-Phase FAPbI3 Perovskites

The highly oriented 2D perovskite templates of n = 1 have typically been created to attain controllable and oriented crystallization of 3D α-phase formamidinium lead triiodide (α-FAPbI3) perovskites. However, the role of methylammonium iodide (MAI), a widely used α-FAPbI3 phase stabilizer, in regulating the growth dynamics of 2D/3D perovskites is generally ignored. Herein, Ruddlesden-Popper type n = 1 2D octylammonium lead iodide (OA2PbI4) perovskites are added into FAPbI3 precursor solution. The template of n = 2 (OA2MAPb2I7), which is spontaneously constructed by the mixture of n = 1 2D and methylammonium chloride (MACl), acts as a skeleton to template the epitaxial growth of α-FAPbI3. However, the volatilization of MACl inevitably causes damage to the 2D structure during thermal annealing. This study reveals that small amounts of less volatile MAI additive enables the creation of stable 2D template, leading to more controlled vertical orientation crystallization. Consequently, the high-quality mixed-dimensional perovskite film delivers a high efficiency of 24.19% together with improved intrinsic stability. This work provides an in-depth understanding of 2D-assisted controlled epitaxial growth of α-FAPbI3.

Surface Reconstruction with Aprotic Trimethylsulfonium Iodide for Efficient and Stable Perovskite Solar Cells

Organic ammonium salts are widely used for surface passivation to enhance the photovoltaic (PV) performance and stability of perovskite solar cells (PSCs). However, the protic nature of ammonium units results in the quick degradation of perovskites due to the hydrogen bonding interaction with water molecules. Recently, organo-sulfur compounds have attracted growing interest as passivation layers on three-dimensional perovskites due to their moisture-resistive behavior. Herein, trimethylsulfonium iodide (TMSI), an aprotic S-based organic compound, is employed for surface modification of methylammonium lead iodide-based PSCs to impede moisture penetration, improve charge transfer, and passivate surface defects. The TMSI effectively passivates uncoordinated Pb through Pb···S interactions, and the optimized PSC exhibits a power conversion efficiency (PCE) of 21.03% with an open-circuit voltage of ca. 1.13 V under one-sun illumination, while it reached up to 37.58 and 37.69% under low-intensity indoor illuminations, 1000 and 2000 lx with LED 5000 K, respectively. TMSI-treated cells display enhanced device stability by retaining 92.7% of their initial PCE after 50 days of storage in ambient conditions. This study provides a novel and effective surface reconstruction strategy with aprotic materials to improve PV performance and device stability in PSCs.

Facet-Dependent Passivation for Efficient Perovskite Solar Cells

Understanding the interplay between the surface structure and the passivation materials and their effects associated with surface structure modification is of fundamental importance; however, it remains an unsolved problem in the perovskite passivation field. Here, we report a surface passivation principle for efficient perovskite solar cells via a facet-dependent passivation phenomenon. The passivation process selectively occurs on facets, which is observed with various post-treatment materials with different functionality, and the atomic arrangements of the facets determine the alignments of the passivation layers. The profound understanding of facet-dependent passivation leads to the finding of 2-amidinopyridine hydroiodide as the material for a uniform and effective passivation on both (100) and (111) facets. Consequently, we achieved perovskite solar cells with an efficiency of 25.10% and enhanced stability. The concept of facet-dependent passivation can provide an important clue on unidentified passivation principles for perovskite materials and a novel means to enhance the performance and stability of perovskite-based devices.

Improved Crystallization of Lead Halide Perovskite in Two-Step Growth Method by Polymer-Assisted "Slow-Release Effect"

Fast reaction between organic salt and lead iodide always leads to small perovskite crystallites and concentrated defects. Here, polyacrylic acid is blended with organic salt, so as to regulate the crystallization in a two-step growth method. It is observed that addition of polyacrylic acid retards aggregation and crystallization behavior of the organic salt, and slows down the reaction rate between organic salt and PbI₂ , by which "slow-release effect" is defined. Such effect improves crystallization of perovskite. X-ray diffraction study shows that, after addition of 2 mm polyacrylic acid, average crystallite size of perovskite increases from ≈40 to ≈90 nm, meanwhile, grain size increases. Thermal admittance spectroscopy study shows that trap density is reduced by nearly one order (especially for deep energy levels). Due to the improved crystallization and reduced trap density, charge recombination is obviously reduced, while lifetime of charge carriers in perovskite film and devices are prolonged, according to time-resolved photoluminescence and transient photo-voltage decay curve tests, respectively. Accordingly, power conversion efficiency of the device is promoted from 19.96 (±0.41)% to 21.84 (±0.25)% (with a champion efficiency of 22.31%), and further elevated to 24.19% after surface modification by octylammonium iodide.

Improved Thermal Stability and Film Uniformity of Halide Perovskite by Confinement Effect brought by Polymer Chains of Polyvinyl Pyrrolidone

Polyvinyl pyrrolidone (PVP) is doped to PbI₂ and organic salt during two-step growth of halideperovskite. It is observed that PVP molecules can interact with both PbI₂ and organic salt, reduce the aggregation and crystallization of the two, and then slow down the coarsening rate of perovskite. As doping concentration increases from 0 to 1 mM in organic salt, average crystallite size of perovskite decreases monotonously from 90 to 34 nm; Surface fluctuation reduces from 259.9 to 179.8 nm at first, and then increases; Similarly, surface roughness decreases from 45.55 to 26.64 nm at first, and then rises. Accordingly, a kind of "confinement effect" is resolved to crystallite growth and surface fluctuation/roughness, which helps to build compact and uniform perovskite film. Density of trap states (t-DOS) is cut down by ≈60% at moderate doping  (0.2 mM). Due to the "confinement effect", power conversion efficiency of perovskite solar cells is improved from 19.46 (±2.80) % to 21.50 (±0.99) %, and further improved to 24.11% after surface modification. Meanwhile, "confinement effect" strengthens crystallite/grain boundaries and improves thermal stability of both film and device. T₈₀ of device increases to 120 h, compared to 50 h for reference ones.

Atomic layer deposition of SnO2 using hydrogen peroxide improves the efficiency and stability of perovskite solar cells

Low-temperature processed SnO₂ is a promising electron transporting layer in perovskite solar cells (PSCs) due to its optoelectronic advantage. Atomic layer deposition (ALD) is suitable for forming a conformal SnO₂ layer on a high-haze substrate. However, oxygen vacancy formed by the conventional ALD process using H₂O might have a detrimental effect on the efficiency and stability of PSCs. Here, we report on the photovoltaic performance and stability of PSCs based on the ALD-SnO₂ layer with low oxygen vacancies fabricated via H₂O₂. Compared to the ALD-SnO₂ layer formed using H₂O vapors, the ALD-SnO₂ layer prepared via H₂O₂ shows better electron extraction due to a reduced oxygen vacancy associated with the highly oxidizing nature of H₂O₂. As a result, the power conversion efficiency (PCE) is enhanced from 21.42% for H₂O to 22.34% for H₂O₂ mainly due to an enhanced open-circuit voltage. Operational stability is simultaneously improved, where 89.3% of the initial PCE is maintained after 1000 h under an ambient condition for the H₂O₂-derived ALD SnO₂ as compared to the control device maintaining 72.5% of the initial PCE.

Halide Chemistry in Tin Perovskite Optoelectronics: Bottlenecks and Opportunities

Tin halide perovskites (Sn HaPs) are the top lead-free choice for perovskite optoelectronics, but the oxidation of perovskite Sn2+ to Sn4+ remains a key challenge. However, the role of inconspicuous chemical processes remains underexplored. Specifically, the halide component in Sn HaPs (typically iodide) has been shown to play a key role in dictating device performance and stability due to its high reactivity. Here we describe the impact of native halide chemistry on Sn HaPs. Specifically, molecular halogen formation in Sn HaPs and its influence on degradation is reviewed, emphasising the benefits of iodide substitution for improving stability. Next, the ecological impact of halide products of Sn HaP degradation and its mitigation are considered. The development of visible Sn HaP emitters via halide tuning is also summarised. Lastly, halide defect management and interfacial engineering for Sn HaP devices are discussed. These insights will inspire efficient and robust Sn HaP optoelectronics.

Efficient and Stable Perovskite Solar Cells via CsPF6 Passivation of Perovskite Film Defects

Polycrystalline perovskite films have many fatal defects; defect passivation can improve the performance of perovskite solar cells (PSCs). In this study, the defects in perovskite films are passivated by introducing the pseudohalide salt CsPF₆ into the films. Because the ionic radii of Cs⁺ and PF₆^- are close to those of FA⁺ and I^-, respectively, they can be uniformly doped into perovskite films to passivate the bulk, surface, and grain boundary defects. The photovoltaic performance of the PSCs significantly improved after passivation. Moreover, the photoelectric conversion efficiency increased significantly from 21.36% to 23.15% after passivation. Because of defect passivation, PSCs also exhibit good environmental stability. This study introduces a scheme for improving the photovoltaic performance of PSCs via passivation.