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Perovskite solar cells represent the most attractive emerging photovoltaic technology, but their practical implementation is limited by solar cell devices' low levels of operational stability. The electric field represents one of the key stress factors leading to the fast degradation of perovskite solar cells. To mitigate this issue, one must gain a deep mechanistic understanding of the perovskite aging pathways associated with the action of the electric field. Since degradation processes are spatially heterogeneous, the behaviors of perovskite films under an applied electric field should be visualized with nanoscale resolution. Herein, we report a direct nanoscale visualization of methylammonium (MA+) cation dynamics in methylammonium lead iodide (MAPbI3) films during field-induced degradation, using infrared scattering-type scanning near-field microscopy (IR s-SNOM). The obtained data reveal that the major aging pathways are related to the anodic oxidation of I− and the cathodic reduction of MA+, which finally result in the depletion of organic species in the channel of the device and the formation of Pb. This conclusion was supported by a set of complementary techniques such as time-of-flight secondary ion mass spectrometry (ToF-SIMS), photoluminescence (PL) microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) microanalysis. 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. [ABSTRACT FROM AUTHOR]

The high power-conversion efficiencies of hybrid perovskite solar cells encourage many researchers. However, their limited photostability represents a serious obstacle to the commercialization of this promising technology. Herein, we present an efficient method for improving the intrinsic photostability of a series of commonly used perovskite material formulations such as MAPbI3, FAPbI3, Cs0.12FA0.88PbI3, and Cs0.10MA0.15FA0.75PbI3 through modification with octenidine dihydroiodide (OctI2), which is a widely used antibacterial drug with two substituted pyridyl groups and two cationic centers in its molecular framework. The most impressive stabilizing effects were observed in the case of FAPbI3 and Cs0.12FA0.88PbI3 absorbers that were manifested in significant suppression or even blocking of the undesirable perovskite films' recrystallization and other decomposition pathways upon continuous 110 mW/cm2 light exposure. The achieved material photostability—within 9000 h for the Oct(FA)n−1PbnI3n+1 (n = 40–400) and 20,000 h for Oct(Cs0.12FA0.88)n−1PbnI3n+1 (where n = 40–400) formulations—matches the highest values ever reported for complex lead halides. It is important to note that the stabilizing effect is maintained when OctI2 is used only as a perovskite surface-modifying agent. Using a two-cation perovskite composition as an example, we showed that the performances of the solar cells based on the developed Oct(Cs0.12FA0.88)399Pb400I1201 absorber material are comparable to that of the reference devices based on the unmodified perovskite composition. These findings indicate a great potential of the proposed approach in the design of new highly photostable and efficient light absorbers. We believe that the results of this study will also help to establish important guidelines for the rational material design to improve the operational stability of perovskite solar cells. [ABSTRACT FROM AUTHOR]

[Display omitted] The supramolecular complexation of anthracycline antibiotic ruboxyl with water-soluble fullerene derivative was visualized by scattering scanning near-field optical microscopy, and the effects of this complexation on the antileukemic activity in vivo were evaluated. Treatment of mice with P388 lymphocytic leukemia with ruboxyl resulted in 13% of cured animals, while similar treatment with ruboxyl–fullerene derivative combination caused 63% curing. [ABSTRACT FROM AUTHOR]

The trap state at the surfaces and grain boundaries of perovskite is one of the major obstacles to the further commercialization of flexible perovskite solar cells (FPSCs). Herein, two innovative multifunctional fluorinated propylamine salt 2,2,3,3,3‐pentafluoropropylamine hydrochloride (PFPACl) and 3,3,3‐triflupropylamine hydrochloride (TFPACl) are in situ introduced onto the photo absorbing layer to improve the performance of the FPSCs. The nuclear magnetic resonance (NMR) spectroscopy indicates strong interactions of both PFPACl and TFPACl with the perovskite precursor components. For the first time, the structures of the supramolecular complexes formed by two additives with FAI are deduced from NOESY NMR data, thus pointing to the importance of the preorganization of the perovskite components in solution before film casting. The experiments and density functional theory（DFT) calculations reveal that PFPACl is likely dissociated more into the form of R‐NH3+‐Cl− due to the higher electronegativity of the fluoroalkyl tail. Therefore, PFPA+ binds more strongly to VFA defects than TFPA+, and anion Cl− has strong enough interaction with VFAI and uncoordinated Pb2+, leading to homogeneous coverage of PFPACl on the entire surface of the perovskite films and better energy alignment with the hole transport layer. Consequently, PFPACl‐treated FPSCs achieved a relatively high PCE of 23.59% with excellent mechanical robustness and operational stability. [ABSTRACT FROM AUTHOR]

In this work, the local current-voltage characteristics of nanocomposite phase boundaries in the form of a poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) (70/30) matrix filled with conductive polyaniline (PANI) particles are studied by conductive atomic force microscopy. At negative external bias voltages, these dependencies are shown to have an interval with a negative differential resistance. This fact is caused by the switching of ferroelectric polarization of individual nanocrystallites PVDF-TrFE located near the phase boundaries in the amorphous matrix volume. The obtained results confirm assumptions about the memristive properties of the investigated nanocomposites. [ABSTRACT FROM AUTHOR]

The recent success in the development of non-fullerene acceptors (NFAs) for organic solar cells (OSCs) encourages the search for novel efficient and complementary donor materials. Moreover, the in-depth understanding of the structure–property correlations for new generations of acceptor and donor materials is of great importance for the further progress in the field of OSCs. In this work the synthesis of a series of star-shaped small molecules based on benzotriindole (BTI) electron-donating core linked through bi– or terthiophene π-spacers to either hexyl dicyanovinyl or 2-ethylhexyl cyanoacetate electron-withdrawing terminal groups (EWGs) is reported. The thermal, optical and electrochemical properties of the molecules were carefully investigated and compared. The molecules were also explored as donor materials in non-fullerene (NF) OSCs in binary blends with well-known NFAs such as IDIC or Y6. The huge impact of the donor molecular structure on the device performance (up to 6 times difference in power conversion efficiency (PCE)) was evaluated due to significant difference in the active layer morphologies, which was successfully proved via scanning near-field infrared microscopy technique. The results obtained in this work demonstrate high potential of star-shaped BTI-based molecules to be used as donor materials with a new generation of NFAs and can be used for further molecular design of the highly efficient small molecule donors for NF OSCs. [Display omitted] • Donor D–π–A star-shaped molecules were used in non-fullerene OSCs and showed high PCE. • Impact of molecule acceptor groups on molecule properties and OSCs parameters was evaluated. • The π–spacer length has no influence on HOMO energy for this type of molecules. • The morphology of the photoactive layer was investigated using IR-SNOM technique. [ABSTRACT FROM AUTHOR]

[Display omitted] • The modification of perovskites by partial replacement of Pb2+ with Dy2+ was explored. • Incorporation of Dy2+ strongly enhanced resistance of perovskite films to gamma rays. • The presence of Dy2+ suppressed metallic lead Pb0 formation upon radiolysis. • Dy modification improved the tolerance of perovskite films to 8.5 MeV electron beams. • Excellent radiation hardness of Dy-loaded absorbers points to aerospace applications. Continuously growing evidence of the excellent radiation hardness of perovskite solar cells stimulates their intense exploration in the context of potential aerospace applications. However, there is still a very limited understanding of the fundamental aspects such as the mechanisms of the interaction of complex lead halides with different types of ionizing radiation and associated aging pathways, even though this knowledge is essentially important for the development of new materials with improved properties. Herein, we made one of the first steps to fill this gap through a systematic study of the aging behavior of two perovskite absorber materials under exposure to three different stressors: 60Co gamma-rays, 8.5 MeV electron fluences, and light. The application of a set of complementary spectroscopy and microscopy techniques allowed us to identify and compare perovskite degradation pathways caused by each type of the ionizing radiation. In particular, radiation-induced phase segregation with the formation of δ-phases of CsPbI 3 and FAPbI 3 appears to be a common route in the case of double cation perovskites. Most importantly, we have revealed that the incorporation of dysprosium cations as a replacement of 1 % of Pb2+ ions in the Cs 0.12 FA 0.88 Pb 0.99 Dy 0.01 I 3 material formulation results in a remarkably improved radiation hardness: this modification blocks the formation of metallic lead and strongly suppresses segregation of Cs-rich and FA-rich phases in perovskite films under exposure to gamma rays or high-energy electrons. Thus, these results open up a promising research direction for designing radiation-resistant perovskite absorbers through rational compositional engineering. [ABSTRACT FROM AUTHOR]

A series of four new oligomeric derivatives of NFA , NFA(S) , NFA(Se) and NFA(N) with terminal perylene diimide groups modified with heteroatoms of S, Se, and N, were successfully synthesized and fully characterized by a variety of physicochemical methods. Due to deep LUMO levels, all compounds have an electron-acceptor character, which allows them to perform as electron transport compounds in perovskite solar cells of p-i-n architecture. The highest efficiency of 17.23 % was delivered by the solar cells with NFA(Se) electron transporting layer. [Display omitted] • A series of new oligomers with terminal perylene diimide groups modified with heteroatoms of S, Se, and N, were synthesized. • Optical and electronic properties of the new compounds were studied. • All the compounds were studied as new type materials for electron transport layer for perovskite solar cells. • The highest efficiency of 17.23 % was delivered by the solar cells with NFA(Se) electron transporting layer. [ABSTRACT FROM AUTHOR]

Multilayer (14 layers, 115–122 nm thick each) BiFeO3/CoFe2O4/substrate (BFO/CFO) and CoFe2O4/BiFeO3/substrate (CFO/BFO) nanocomposites were obtained by the method of sol-gel synthesis. It is shown that all samples of the obtained nanocomposites have multiferroic properties at room temperature. At the same time, there is a clearly demonstrated effect of the layering order on the values of remnant polarization and magnetization of these samples. This influence originates from the much smaller size of the crystallites in the BiFeO3 layers for the samples deposited in order (BFO/CFO) at various annealing temperatures (700, 725, and 750 °C). [ABSTRACT FROM AUTHOR]

Perovskite solar cells represent a highly promising third-generation photovoltaic technology. However, their practical implementation is hindered by low device operational stability, mostly related to facile degradation of the absorber materials under exposure to light and elevated temperatures. Improving the intrinsic stability of complex lead halides is a big scientific challenge, which might be addressed using various "molecular modifiers". These modifiers are usually represented by some additives undergoing strong interactions with the perovskite absorber material, resulting in enhanced solar cell efficiency and/or operational stability. Herein, we present a derivative of 1,4,6,10-tetraazaadamantane, NAdCl, as a promising molecular modifier for lead halide perovskites. NAdCl spectacularly improved both the thermal and photochemical stability of methylammonium lead iodide (MAPbI3) films and, most importantly, prevented the formation of metallic lead Pb0 as a photolysis product. NAdCl improves the electronic quality of perovskite films by healing the traps for charge carriers. Furthermore, it strongly interacts with the perovskite framework and most likely stabilizes undercoordinated Pb2+ ions, which are responsible for Pb0 formation under light exposure. The obtained results feature 1,4,6,10-tetraazaadamantane derivatives as highly promising molecular modifiers that might help to improve the operational lifetime of perovskite solar cells and facilitate the practical implementation of this photovoltaic technology. [ABSTRACT FROM AUTHOR]