The development of solvent-free fabrication methods is critical for advancing the manufacturability and environmental sustainability of perovskite photovoltaics. Here, we introduce a solvent-free process for depositing high-performance nickel oxide (NiOx) hole-transport layers (HTLs) via the thermal evaporation of a NiOx>1(OH)(y) precursor. Comprehensive surface analysis reveals that the evaporated films possess an optimal Ni2+/Ni3+ oxidation state ratio for charge transport and a high concentration of surface Ni-OH groups, which facilitate the subsequent adsorption of a 2PACz self-assembled monolayer (SAM). The excellent uniformity and pinhole-free morphology of the resulting NiOx/2PACz stack are confirmed by conductive AFM, IR nano-spectroscopy (s-SNOM), and electron microscopy. By optimizing the NiOx thickness and annealing conditions, we integrate this stack into efficient p-i-n perovskite solar cells (PSCs), achieving power conversion efficiencies approaching 20.6%. This work establishes thermally evaporated NiOx as a viable and high-quality component paving the way toward the fabrication of efficient fully vacuum-processed p-i-n PSCs, providing a critical step toward industrially relevant production.

The operational instability of perovskite solar cells (PSCs), particularly at realistically high temperatures of >50 degrees C, remains a primary barrier to their commercialization. Methylammonium lead iodide (MAPbI3) is a prototypic perovskite absorber material notoriously susceptible to degradation under moisture, light, and heat, thus representing an ideal model system for designing new materials and device configurations for operational stability improvement. In this work, we address this critical issue by engineering a stable MAPbI3/tungsten(vi) oxide (WOx) interface within a p-i-n device architecture. Depositing the WOx electron transport layer (ETL) directly atop the perovskite absorber or using C60 as an interlayer provides decent power conversion efficiencies (PCEs) of 19.2%. Infrared scattering-type scanning near-field optical microscopy (IR s-SNOM) reveals that the thermally evaporated WOx forms a highly uniform and compact layer, providing complete coverage of the underlying perovskite. The devices with a simple structure (ITO/PTAA/MAPbI3/WOx/Al) demonstrate exceptional operational stability, retaining >70% of the initial performance after 4600 hours of continuous light soaking (100 mW cm(-2)) at 60 degrees C under open circuit conditions and without encapsulation. We attribute this stability to the formation of a robust interface between PbI2 and WOx, which remains intact under illumination. Crucially, the WOx layer acts as a protective barrier, effectively suppressing the evaporation of volatile decomposition products and preventing electrode corrosion. This work establishes the application of the tungsten oxide ETL as a highly promising strategy for achieving long-term operational stability in p-i-n PSCs, which is strongly demanded for commercial applications of perovskite photovoltaics.

Mixing univalent cations (Cs, MA, and FA) results in remarkable stabilization: both MA and FA cations endured the field-induced degradation much better than in the single-cation films.

The article presents the results of studying the effect of heterovalent doping on the local atomic and electronic structure and photochemical stability of multivalent $\mathbf{C s}_{\mathbf{0. 1 2}} \mathbf{F A}_{\mathbf{0. 8 8}} \mathbf{P b I}_{\mathbf{3}}$ perovskite after light soaking with 4000 hours at 0.9 Sun. Monovalent ($\mathbf{A g}^{\boldsymbol{+}}$) and trivalent ($\mathbf{Y}^{\mathbf{3 +}}, \mathbf{I n}^{\mathbf{3 +}}, \mathbf{S b}^{\mathbf{3 +}}, \mathbf{B i}^{\mathbf{3 +}}$) metals are chosen as dopants at a concentration of 1% to avoid the impurity segregation and secondary phase formation. It is found that the I:Pb ratio does not change as a result of doping, which excluded the substitution of Pb metal in perovskite. It is revealed that XPS N 1s, Pb 4f and I 3d spectra show the photochemical degradation of perovskites with formation of PbI2 contribution upon the introduction of $\mathbf{A g}^{+}, \mathbf{Y}^{\mathbf{3 +}}, \mathbf{S b}^{\mathbf{3 +}}$ and $\mathbf{B i}^{\mathbf{3 +}}$ dopants. On the other hand, for the $\mathrm{In}^{3+}{ }^{3+} \mathrm{Cs}_{0.12} \mathrm{FA}_{0.88} \mathrm{PbI}_{3}$ system the high resistance to light soaking up to 4000 hours dose is found and associated with the placement of this impurity on the grain surface and realization of hard Lewis base passivation.

The results of XPS studies of photochemical degradation of MAPbI3 and MASnI3 perovskites are found to be different. XPS Pb 4f spectra show that the oxidation state of metal atoms in as prepared APbX3 (A = MA, FA, Cs; X = I, Br) is higher than in Pb metal and lower than in PbI2 and the subsequent light soaking up to 1000 h induces the decomposition of perovskites with formation of PbI2 and Pb0 degradation products. On the other hand, the binding energy of XPS Sn 3d spectra of the initial ASnI3 (A = MA, FA) exhibit a coincidence with spectrum of SnI2 and following photochemical treatment leads to the release more stable SnI4 phase. According to DFT calculations of model CsPbI3 and CsSnI3 perovskites and binary PbI2, SnI2, SnI4 halides these differences are due to the narrower energy gap of Sn-perovskite compared to Pb-counterpart induces the formation of metal vacancies and instabilty of Sn2+ ions providing the light induced Sn2+→Sn4+ transition. The photochemical degradation of MAPbI3 and MASnI3 is found as a two-step process: (1) light-induced decomposition into MAI and PbI2/SnI2, followed (2) by decay of PbI2 on Pb0 + I2↑ and oxidation of SnI2 to SnI4.

The partial substitution of Pb2 + with Ge2+ in lead halide perovskites and its impact on photostability and radiation resistance are systematically investigated. X-ray photoelectron spectroscopy (XPS) studies of MAPb(1-& khcy;)Ge(& khcy;)I(3) reveal that incorporating Ge leads to self-doping, driven by the formation of Ge4+ within the perovskite lattice under anoxic conditions. This mechanism enhances hole carrier density, offering a potential route for improving electrical conductivity. At higher Ge concentrations (>5 %), however, excess germanium segregates to grain surfaces as a GeI2 layer, rather than incorporating into the lattice. In mixed-cation Cs(0.12)FA(0.88)Pb(0.99)Ge(0.01)I(3) films, Ge doping reduces grain size and significantly improves photostability, evidenced by a optical absorption and sustained photoluminescence after extended light soaking. Both undoped and Ge-doped perovskites demonstrate exceptional radiation hardness under 8.2 MeV electron irradiation, maintaining optical properties at fluences equivalent to prolonged space exposure. Nonetheless, irradiated films exhibit surface depletion of Pb and accumulation of FA(+) decomposition products, attributed to radiation-enhanced ion migration. Moreover Ge-doped perovskite show the pronounced iodine vacancies formation under electron beams. These findings elucidate the dual role of Ge as a self-doping agent and a grain-boundary modifier, providing critical insights for designing stable, high-performance perovskite optoelectronic devices.

To advance metal halide perovskite (MHP) optoelectronics beyond efficiency, international collaboration is essential, with an emphasis on stability, cost, and scalability. MHPs demonstrate remarkable stability in extreme space-level radiation; nevertheless, their stability under everyday conditions, particularly when exposed to humidity and thermal cycling, remains a significant challenge. Strategies such as low-dimensional interface passivation, quantum-dot integration, and in situ synchrotron studies are among the methods emphasized in this perspective to mitigate these problems. We propose pathways of collaborative research aimed at accelerating the development of durable, high-performance perovskite devices by synthesizing insights from the broader literature in conjunction with findings from a BRICS joint initiative project.

A series of (BDD-X)n conjugated polymers, comprised of 5,7-bis(2-ethylhexyl)benzo[1,2-c:4,5-c ']dithiophene-4,8-dione (BDD) and X = B (P1), X = TBT (P2), and X = TBTBT (P3), where T = thiophene and B = benzo[c][1,2,5]thiadiazole, have been synthesized and applied as dopant-free hole-transport layer materials in perovskite solar cells (PSCs). We explored the effect of the molecular structure of the block X on the optical and electronic properties of the polymers, the nanoscale morphology of their films, and the impact of all these parameters on the performance of the polymers in PSCs. As a result, using the polymer P1 with the simplest molecular architecture provided a power conversion efficiency (PCE) of 20.1% in solar cells, thus outperforming devices assembled with the more sophisticated polymers P2-P3 or the reference poly(triarylamine)-based hole-transport materials. The enhanced device performance is attributed to a better HOMO alignment of P1 with respect to the perovskite valence band, a low concentration of defects and suppressed carrier recombination at the P1/perovskite interface and, most importantly, a highly uniform film structure, as revealed by atomic force microscopy and infrared scattering near-field optical microscopy (IR s-SNOM) techniques. The supramolecular interactions of the building blocks of polymers P1-P3 with the perovskite films, resulting in the passivation of surface defects, were further studied by density functional theory calculations.

The photostability of CsPb0.95M0.1/nI2Br films modified with 30 different substituent Mn+ cations was systematically investigated. It was shown for the first time that light-induced halide phase segregation in CsPbI2Br perovskite films could be completely suppressed by partial replacement of Pb2+ with rationally selected cations: Sr2+, Sn2+, In3+ and Bi3+. The obtained results open the door for the development of photostable wide-bandgap perovskite semiconductors required for high-efficiency tandem solar cells.

Novel polymers composed of thiophene units combined with non-fluorinated and fluorinated 2,1,3-benzothiadiazole units were synthesized and investigated as hole transport materials in perovskite solar cells. The impact of backbone fluorination on the optical and electronic properties of the resulting materials as well as the nanoscale morphology of their films deposited on the perovskite absorber layer was elucidated. The fluorinated polymer provided a superior power conversion efficiency of 18.6% coupled with high open-circuit voltage (VOC = 1.047 V)and short-circuit current (JSC= 23.4 mA cm-2).

The partial Pb2+ substitution with Cu+ ions has been thoroughly applied as an approach to produce new absorber materials with enhanced light and radiation hardness required for potential aerospace applications of perovskite solar cells. X-ray photoelectron spectroscopy revealed that Cu+ ions are partially integrated into the crystal lattice of MAPbI3 on the surface of perovskite grains and induce p-doping effect, which is crucial for a range of applications. Importantly, the presence of Cu+ enhances photostability of perovskite films and blocks the formation of metallic lead as a photolysis product. Furthermore, we have carried out one of the first studies on the radiation hardness of complex lead halides exposed to two different stressors: gamma-rays and 8.5 MeV electron beams. The obtained results demonstrate that Cu+ doping alters completely the radiation-induced degradation pathways of the double cation perovskite. Indeed, while Cs0.12FA0.88PbI3 degrades mostly with segregation of delta-phase of FAPbI3 forming a Cs-rich perovskite phase, the Cs0.12FA0.88Pb0.99Cu0.01I2.99 films tend to expel delta-CsPbI3 and produce FA-rich perovskite phase, which shows impressive tolerance to both gamma-rays and high energy electrons. The beneficial effect of copper ion incorporation on the stability of lead halide perovskite solar cells under light soaking and gamma-ray irradiation conditions has been shown. The discovered possibility of controlling the electronic properties and major materials degradation pathways through minor modification of their chemical composition (e.g., replacing 1% of Pb2+ with Cu+) opens up tremendous opportunities for engineering new perovskite absorber compositions with significantly improved properties for both terrestrial and aerospace applications.image

Substitution of Pb2+ ions in lead halide perovskite Cs0.12FA0.88PbI3 (FA is formamidinium cation) was investigated to address the issues of its phase stability and photostability. The incorporation of optimally selected Nd3+, Tb3+ and Er3+ cations into Cs0.12FA0.88Pb0.99M0.02/nI3 films significantly suppressed the light-induced recrystallization and photodegradation, maintaining the morphology, optical properties and phase composition after 9000 h of light exposure, and improved the efficiency and operational stability of perovskite solar cells.

Herein, we report the nanoscale cations dynamics in Cs 0.1 MA 0.15 FA 0.75 PbI 3 films during the electric-field-induced aging process using infrared scattering scanning near-field microscopy (IR s-SNOM) combined with a series of complementary analytical techniques such as PL-microscopy, SEM/EDX and ToF-SIMS. The revealed major field- induced aging pathways are related to the anodic oxidation of I- and the cathodic reduction of MA+ and FA+, which finally result in the depletion of organic species in the device channel and the formation of metallic lead. FA+ cations show significantly higher stability with respect to electrochemical reduction as compared to MA+ cations. Formamidinium cations are preserved on the surface of the near-cathode film area even after 40 days of the 1 V/mu m field exposure, while MA+ cations demonstrate complete decomposition after 24 days. The obtained results demonstrate that IR s-SNOM represents a powerful technique for studying the spatially resolved field- induced degradation dynamics of hybrid perovskite absorbers and the identification of more promising materials resistant to the electric field.

Herein, we explored the application of perylenetetracarboxylic dianhydride (PTCDA) electron transport material for inverted perovskite solar cells (PSCs). We obtained a modest power conversion efficiency (PCE) of 15.0% using PTCDA alone to form electron-transport layer (ETL) of p-i-n devices, whereas the combination of PCTDA with C60 within a binary ETL delivered PCE of 19.8%. The improved efficiency reached with binary ETL can be attributed to its ability to facilitate charge transfer and passivate traps the surface of the perovskite layer thus reducing recombination losses at the absorber/ETL interface. Further insights were provided by IR s-SNOM microscopy, which revealed that the binary C60/PTCDA ETL has a highly uniform and homogeneous structure with low density of defects and pinholes, thus ensuring effective isolation of MAPbI3 and effective operation of PSCs. Moreover, the binary C60/PTCDA ETL improved the stability of PSCs under ambient conditions, so the devices exhibited no signs of degradation after 1000h. These findings feature the potential of PTCDA as a promising organic component for designing engineered multicomponent ETLs for improving the performance and stability of PSCs.

A crucial problem of the photoinduced degradation of perovskite semiconductors based on complex lead halides has been addressed here by suppressing PbI2 photolysis to metallic lead. The systematic screening of >30 modifying cations introduced as substituents for 5% of Pb2+ in the PbI2 composition has revealed their tremendous effects on the rate of material degradation under light exposure. Thus, the most successful stabilizing cations could maintain a high absorbance of the Pb0.95M0.1/nI2 films and block Pb0 formation after 400 h of continuous illumination, when the non-modified PbI2 films completely decomposed to Pb0 and I2. The obtained results present a promising solution for the problem of metallic lead formation in the active layer of perovskite solar cells during their operation, which can pave the way for the development of a new generation of highly efficient and stable perovskite photovoltaics.

Herein, we have proposed a novel tridentate chelation strategy to manage the excessive amount of unreacted PbI 2 in perovskite films, achieving a inverted PSC device with a PCE of 25.66% by sequential deposition method.

A new method for visualization of uncoordinated lead (Pb2+) in solution processed polycrystalline halide perovskite films is presented. The method is based on the measurements of XPS spectra with high energy resolution, which show a narrowing of the low-energy part of the Pb 4f-core level spectra due to passivation of halide vacancies with soft and hard Lewis base doping and reduction of contribution of uncoordinated lead (Pb2+) at binding energy of similar to 137.8 eV. Based on XPS Pb 4f-spectra measurements the influence of size of hard Lewis base metal iodides on the passivation of surface defects in MAPbI(3) perovskite is discussed. It is found that at low concentrations (1-5 %) CaI2, BaI2, AgI with metal ionic radius >= 1.0 & Aring; the metal atoms substitute the coordinated Pb2+ atoms whereas at higher concentrations they are located at grain boundaries and passivate the uncoordinated lead sites. For hard Lewis base metal iodides with small ionic radii (0.7-0.8 & Aring;) (MnI2, FeI2, CuI) the situation is quite different and metals occupy the interstitial positions keeping the uncoordinated Pb2+ ions to be unchanged. The use of appropriate charge-transport layers and soft Lewis base molecular modifiers can improve the crystallization of perovskite films by reducing the number of defects formed, which is also reflected in the XPS Pb 4f(7/2) spectra.

Efficient and stable inverted perovskite solar cells (PSCs) have combined many advantages which makes them particularly promising, with potential for rapid commercialization. However, there are still some challenges to overcome, including poor energy level alignment between perovskite and charge transport interlayers, the presence of deleterious interface defects, and the hydrophobicity of NiOx/PTAA-based double hole transport layer which seriously depress the improvement of the power conversion efficiency (PCE) and stability of PSCs. Presently, we utilized a passivating salt, tyramine hydrochloride (TACl), to modify the NiOx/PTAA film and both perovskite absorber interfaces. The modification using TACl resulted in improving wettability of the PTAA film through the formation of cid-base interactions at solvation model and nonconventional -OH & sdot;& sdot;& sdot;pi hydrogen bonds as well as optimizing energy level alignment, a lower rate of nonradiative recombination, and a markedly improved crystal quality of the perovskite films. Finally, we obtained a NiOx/PTAA-based inverted PSCs device with a PCE of 23.35 %. Our unencapsulated optimized devices maintained 90.2 % of their initial PCE after 1000 h of MPPT monitoring. In addition, we prepared the PSCs devices with the bandgaps of 1.56 eV and 1.68 eV, which achieved PCEs of 25.13 % and 22.36 %, respectively.