Scaling high-efficiency perovskite solar cells into commercially viable modules remains challenging. Here, we demonstrate a seed-primed, vacuum-assisted crystallization (S-VAC) strategy that links oleylamine-induced alpha-phase nanocrystal seeding to vacuum-driven vertical crystal growth. Complementary in situ characterization, including time-resolved GIWAXS, solution-state NMR, and dynamic light scattering (DLS), reveals that oleylamine forms uniform approximate to 1.7 nm alpha-phase seeds in the precursor solution via hydrogen bonding with FA(+) cations and steric stabilization. These seeds prime the substrate for controlled, single-crystal-like vertical growth under low-pressure vacuum processing, thereby eliminating the need for toxic antisolvents. The resulting monolithic perovskite films exhibit strong (100) texture and high uniformity across 15 x 15 cm(2) substrates. Using S-VAC, we achieve a power conversion efficiency (PCE) of 23.2% for 2.5 x 2.5 cm(2) devices and a certified efficiency of 19.1% for 15 x 15 cm(2) mini-modules. Encapsulated modules retain >94% of their initial efficiency after one year of continuous outdoor operation. By establishing a molecular-level basis for oleylamine-assisted seed formation and demonstrating scalable, antisolvent-free processing, this work advances seed-assisted crystallization and supports the practical commercialization of robust and sustainable perovskite photovoltaics.

Integration of sensing, memory, and computing functionalities within a single device is a key step towards the development of efficient and compact artificial visual systems. Halide perovskite based memristors are promising candidates for such neuromorphic platforms due to their inherent optoelectronic properties and resistive switching capabilities. Using lead free layered double perovskites based on 1,4-phenylenedimethylammonium (PDMA) and benzylammonium (BzA) of (PDMA)2AgBiX8 and (BzA)4AgBiX8 (X = I and Br) compositions, we show that field and light-driven migration of halide ions and lattice incorporated Ag+ governs resistive switching and synaptic processes through an intrinsic mechanism, enabling electrical and optical synaptic responses. Depending on how ionic redistribution is stabilized or allowed to relax under different electrode and architectural boundary conditions, the same material exhibits both non-volatile memory and diffusive (volatile) switching essential for mimicking dynamic synaptic and neuronal processes. In solar cell configurations, the built-in junction field couples photocarrier generation with ionic motion, allowing zero-bias optical synaptic plasticity and self-powered operation for potential in-sensor computing. Electrical and optical synaptic responses emerge from this unified ion-dynamic process. Electrode and temperature dependence studies, transient measurements, polarity-switching analysis, and impedance spectroscopy provide consistent mechanistic signatures across operating modes. These findings position lead-free layered double perovskites as multifunctional and sustainable materials for neuromorphic technologies.

Metal halide perovskite solar cells have considerable potential for next-generation solar power production. However, if not controlled, the migration of mobile ions can hamper the stability of perovskite solar cells. Intensive research efforts have devised methods of suppressing ion migration and degradation in perovskite materials, resulting in solar cells that are stable over thousands of hours during accelerated ageing testing. Here, we review the chemical origins of ion migration, its effect on material and device performance and stability, and strategies to mitigate its impact. Ion migration originates in the soft lattice of the halide perovskite framework and its low defect-formation energy, but there are many different strategies to reduce its effects, from compositional engineering of materials and device architecture changes to additives and strain engineering. The field has made great progress in understanding the origin and properties of mobile ions in halide perovskites and has improved operational stability beyond expectations. Nonetheless, there are still ample opportunities to further improve the long-term durability of perovskite solar cells, either by reducing ion migration or its effect on solar cell efficiency. Ion migration plays a crucial role in perovskite solar cells. This Review covers its mechanisms, impact on device performance and degradation, measurement techniques, and emerging strategies towards controlling ion migration.

Metal-free halide perovskites have recently emerged as promising candidates for optoelectronic applications. However, their synthesis has largely depended on water-based single-crystal growth that limits material diversity, scalability, and practical implementation. Here, we present a mechanochemical route to synthesize N,N-diazabicyclo[2.2.2]octonium (H-DABCO)-based halide perovskites from the (DABCO)(NH4)X3 (X = I, Br) compositions. The structural properties were confirmed by X-ray diffraction and solid-state nuclear magnetic resonance spectroscopy. Thin films were prepared from mechanosynthetic powders by spin-coating and characterized by in-situ grazing incidence wide-angle scattering measurements, as well as by UV-vis absorption and steady-state photoluminescence spectroscopy. This mechanosynthetic strategy provides a scalable, environmentally friendly pathway to broaden the scope of metal-free perovskites and advance their potential in sustainable optoelectronic technologies.

Mixed ionic-electronic conductivity of metal halide perovskites is a critical factor determining their application in optoelectronics, as well as the emerging field of optoionics. In particular, ionic migration in response to voltage bias and light contributes to the operational instability of halide perovskite materials and devices. A promising strategy to control ion migration is dimensional reduction, achieved by incorporating bulky organic cations between inorganic slabs to form two-dimensional or layered hybrid halide perovskites. In this perspective article, we discuss the mixed conductivity of layered halide perovskite materials and the impact on the operational stability of perovskite optoelectronics and emerging applications.

In the quest for stable, eco-friendly, lead-free halide perovskites, layered double perovskite semiconductors are promising derivatives that remain underexploited. We demonstrate the use of mechanosynthesis to access these materials for silver(I) and bismuth(III) analogues incorporating benzylammonium and 1,4-phenylenedimethylammonium bromide cations in Ruddlesden-Popper and Dion-Jacobson phases, respectively. Their thin films were fabricated and analysed by a combination of techniques, demonstrating the potential use in thin-film opto(electro)ionics.

The observation of reversible de-mixing phenomena in mixed-halide perovskites under illumination is one of the most challenging as well as intriguing aspects of this class of materials. On the one hand, it poses critical constraints to the compositional space that allows reliable design of absorbers for perovskite photovoltaics. On the other hand, it holds potential for the development of novel optoionic devices where an ionic response is triggered via optical stimuli. Funda-mental questions about the origin of such photo de-mixing process remain unanswered, both in terms of its mechanism as well as thermodynamic description. Here, we relate in-situ measurements of ionic and electronic transport of mixed bromide-iodide perovskite thin films performed during photo de-mixing with the evolution of their optical and morpho-logical properties. The results point to the definition of different stages of the de-mixing process which, based on micros-copy and spectroscopic measurements, we assign to regimes of spinodal decomposition and nucleation of quasi-equilibrium iodide- and bromide-rich phases. Combined with density functional theory calculations, we explore the role of dimensionality in the mechanism and reversibility of photo de-mixing and dark re-mixing processes, referring to elec-tronic and ionic contributions to the de-mixing driving force. Additionally, our data emphasizes the role of the surface, as significantly different de-mixing dynamics, in terms of extent and reversibility, are observed for films with or without encapsulation. Our comprehensive analysis of transport, phase and optical properties of mixed-halide perovskites pro-vides guidelines for future materials design as well as for the more general fundamental understanding of light-induced ionic phenomena.

Brain-inspired neuromorphic systems emerged at the interface of neurosciences, material sciences, and electronics. This viewpoint explores this disciplinary intersection, ranging from its biological inspiration to the translation of underlying principles into material and artificial device engineering, while discussing ongoing challenges and opportunities for fundamental or technological breakthroughs. This contribution reflects the perspectives of Juan Bisquert, a leading expert in materials science and electrochemical systems, and Michele Giugliano, a specialist in neuroscience and neuromorphic computing. Their dialogue is moderated and harmonized by Jovana V. Milić, whose interdisciplinary expertise bridges chemical and biological sciences.

Chirality in hybrid perovskite semiconductors can advance their application in modern electronics, but their production — traditionally involving the incorporation of chiral organic cations into the perovskite frameworks — can be challenging and has certain scope limitations. Now, remote chirality transfer in low-dimensional perovskites has emerged as an alternative strategy for inducing chirality in hybrid metal halide semiconductors.

Hybrid metal halide perovskites have emerged as some of the leading semiconductors in photovoltaics. Despite their remarkable power conversion efficiencies, these materials remain unstable under device operating conditions. One of the main instabilities relates to the interface with the contact layers in photovoltaic devices, such as metal oxides. We rely on halogen bonding (XB) using 1,4-diiodotetrafluorobenzene (TFDIB) to modulate the interface of the TiO2 electron-transport layer, demonstrating the improvement of perovskite solar cell operational stability. Furthermore, we complement this strategy with the use of iodo-functionalized Zn-phthalocyanine modulator of the hole-transporting material, which passivate the interface while enhancing the power conversion efficiency, showcasing the potential of XB in hybrid photovoltaics.

Hybrid halide perovskites are among the most promising candidates for next‐generation photovoltaics. The most investigated perovskite solar cells are lead based, which poses environmental concerns, making finding sustainable alternatives a pressing issue. Tin‐based halide perovskites are attracting interest as an alternative. However, their application in photovoltaics is hindered by the high concentration of defects and sensitivity to oxidation, compromising their performance and stability. Herein, perfluoroarene organic cations, namely 2‐(perfluorophenyl)methylammonium (F‐BNA) and 1,4‐(perfluorophenyl)dimethylammonium (F‐PDMA), are applied to form layered (2D) Ruddlesden–Popper and Dion–Jacobson tin‐based perovskites, respectively. Following a detailed structural and optoelectronic characterization, the perfluoroarenes are applied to formamidinium (FA)‐based FASnI 3 perovskite solar cells and an effective solvent is identified for their processing, 2‐pentanol. While F‐PDMA forms a 2D/3D heterostructure, F‐BNA remains assembled as a molecular interlayer, demonstrating higher photovoltaic performance with limited operational stability. This challenges the conventional role of mixed‐dimensional heterostructures in tin perovskite photovoltaics and opens new perspectives for advanced material design and device engineering.

Hybrid organic-inorganic layered (2D) halide perovskites have demonstrated advantages in improving the performance and stability of perovskite solar cells, and there is an ongoing interest in tailoring organic cations for their application in photovoltaics. We apply tailored molecular systems based on perfluorinated benzylammonium (F-BNA) and 1,4-phenylenedimethylammonium (F-PDMA) cations, forming Ruddlesden-Popper and Dion-Jacobson perovskite phases, respectively, at the interface with 3D perovskite layers in conventional n-i-p perovskite solar cells. The characteristics of 2D/3D perovskite phases are investigated through a combination of techniques including X-ray diffraction, UV-vis absorption, and photoluminescence spectroscopy. We demonstrate the beneficial effects of perfluoroarene perovskite phases in improving the stability and performance toward advancing photovoltaics.

Metal halide perovskites have become the leading semiconductors for new-generation optoelectronics. However, they are primarily based on toxic lead components, which pose environmental concerns. To address this critical limitation, there is an effort to design alternative lead-free halide perovskite materials. One of the emerging approaches has involved the use of layered (2D) halide double perovskite (LDP) materials incorporating tailored organic spacers within the lead-free perovskite framework based on alternative monovalent (M I ) and trivalent (M III ) metal cations, such as Ag, Bi, Cu, In, and others. The interactions within the assemblies of these hybrid organic–inorganic structures define the resulting properties. The role of molecular engineering in the development of LDPs and their optoelectronic characteristics is reviewed from the perspective of molecular design, synthesis, and functionality. Their versatility and methods to synthesize LDPs are discussed, as well as emerging applications, revealing challenges, and opportunities for their utility in more sustainable perovskite optoelectronics and beyond.

Perovskite materials are increasingly important in a variety of optoelectronic applications. Some of these functional materials also exhibit ferroelectric properties, making them promising in memory elements, sensors, and energy technologies. While they exhibit extraordinary performances, their instabilities often hinder practical applications and toxic metal components cause environmental concerns. In the last few years, metal-free molecular perovskites (MOPs) have emerged, featuring ferroelectric properties that outperform conventional perovskite ferroelectrics while offering an environmentally friendly and cost-effective alternative relevant to optoelectronics. We review the structural and optoelectronic characteristics of this new class of materials, as well as preparation techniques, with challenges and opportunities for future applications.

Tin-based halide perovskites are emerging as promising alternatives to traditional lead-based perovskites due to their lower bandgaps, decreased toxicity, and comparable chemical properties. These materials offer unique structural and functional benefits for optoelectronic applications and photovoltaics, particularly in their low-dimensional or layered (2D) forms. Recent advancements have improved the solar-to-electric power conversion efficiency of tin-based halide perovskites by relying on organic spacers to control crystallisation and stabilise the materials. The versatility of molecular compositions and structural tuning of layered tin halide perovskites makes them appealing for next-generation photovoltaic technologies. This review highlights the structural characteristics, synthetic methods, and properties of layered tin halide perovskites, providing a comprehensive overview and discussing future prospects for environmentally friendly perovskite photovoltaics.

Hybrid organic-inorganic perovskite solar cells (PSCs) present a leading thin-film photovoltaic technology with superior solar-to-electric power conversion efficiencies. The most effective compositions, however, contain lead cations, which are toxic and pose environmental hazards. One of the alternatives to lead-based perovskite materials is silver bismuth halide analogues. Here, we present a comprehensive investigation of different silver bismuth iodide compositions by means of density functional theory calculations (DFT) as well as X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy measurements. Through our combined experimental and theoretical study, we have discovered that silver bismuth iodides possess several intrinsic limitations, such as limited charge transport and localized electronic states, owing to the presence of vacant sites. Such limitations result in moderate solar cell efficiencies, significantly lower than those of lead halide perovskites. However, we suggest the possibility of increasing efficiencies by adding BiCl3 to the precursor solution, yielding one of the highest efficiencies reported for this class of compounds to date. This highlights the potential of compositional engineering for these lead-free solar cell materials.

The application of perovskite photovoltaics is hampered by issues related to the operational stability upon exposure to external stimuli, such as voltage bias and light. The dynamic control of the properties of perovskite materials in response to light could ensure the durability of perovskite solar cells, which is especially critical at the interface with charge-extraction layers. We have applied a functionalized photochromic material based on spiro-indoline naphthoxazine at the interface with hole-transport layers in the corresponding perovskite solar cells with the aim of stabilizing them in response to voltage bias and light. We demonstrate photoinduced transformation by a combination of techniques, including transient absorption spectroscopy and Kelvin probe force microscopy. As a result, the application of the photochromic derivative offers improvements in photovoltaic performance and operational stability, highlighting the potential of dynamic photochromic strategies in perovskite photovoltaics.

Metal halide perovskites have shown exceptional potential in converting solar energy to electric power in photovoltaics, yet their application is hampered by limited operational stability. This stimulated the development of hybrid layered (two-dimensional, 2D) halide perovskites based on hydrophobic organic spacers, templating perovskite slabs, as a more stable alternative. However, conventional organic spacer cations are electronically insulating, resulting in charge confinement within the inorganic slabs, thus limiting their functionality. This can be ameliorated by extending the π-conjugation of the spacer cations. We demonstrate the capacity to access Ruddlesden-Popper and Dion-Jacobson 2D perovskites incorporating for the first time aryl-acetylene-based (4-ethynylphenyl)methylammonium (BMAA) and buta-1,3-diyne-1,4-diylbis(4,1-phenylene)dimethylammonium (BDAA) spacers, respectively. We assess their unique opto(electro)ionic characteristics by a combination of techniques and apply them in mixed-dimensional perovskite solar cells that show superior device performances with a power conversion efficiency of up to 23 % and higher operational stability, opening the way for multifunctionality in layered hybrid materials and their application.

Perovskite solar cells have garnered significant interest, yet their limited operational stability remains a major challenge. This is especially pronounced at the interface with charge transport layers. In inverted p-i-n perovskite solar cells, fullerene-based electron transport layers pose critical stability issues. This has stimulated the application of low-dimensional perovskite interlayers featuring alkylammonium-based organic spacers that template perovskite slabs to enhance operational stabilities. However, these materials are traditionally based on organic cations that are electronically insulating, limiting charge extraction and device performance. We demonstrate the capacity to access low-dimensional perovskites incorporating electron-accepting naphthalimide- and naphthalenediimide-based spacers and use the corresponding organic moieties to modify or replace fullerene electron-transport layers, forming an electroactive interface that serves charge-transport. This resulted in superior performance with power conversion efficiencies exceeding 20% and enhanced operational stability, highlighting the potential of electroactive interlayers for advancing inverted perovskite solar cells.