Exploring the Effects of the Pb²⁺ Substitution in MAPbI₃ on the Photovoltaic Performance of the Hybrid Perovskite Solar Cells

Here we report a systematic study of the Pb²⁺ substitution in the hybrid iodoplumbate MAPbI₃ with a series of elements affecting optoelectronic, structural, and morphological properties of the system. It has been shown that even partial replacement of lead with Cd²⁺, Zn²⁺, Fe²⁺, Ni²⁺, Co²⁺, In³⁺, Bi³⁺, Sn⁴⁺, and Ti⁴⁺ results in a significant deterioration of the photovoltaic characteristics. On the contrary, Hg-containing hybrid MAPb_1–<i>x</i>Hg_<i>x</i>I₃ salts demonstrated a considerably improved solar cell performance at optimal mercury loading. This result opens up additional dimension in the compositional engineering of the complex lead halides for designing novel photoactive materials with advanced optoelectronic and photovoltaic properties

Exploring the Photovoltaic Performance of All-Inorganic Ag₂PbI₄/PbI₂ Blends

We present an all-inorganic photoactive material composed of Ag₂PbI₄ and PbI₂, which shows unexpectedly good photovoltaic performance in planar junction solar cells delivering external quantum efficiencies of ∼60% and light power conversion efficiencies of ∼3.9%. The revealed characteristics are among the best reported to date for metal halides with nonperovskite crystal structure. Most importantly, the obtained results suggest a possibility of reaching high photovoltaic efficiencies for binary and, probably, also ternary blends of different inorganic semiconductor materials. This approach, resembling the bulk heterojunction concept guiding the development of organic photovoltaics for two decades, opens wide opportunities for rational design of novel inorganic and hybrid materials for efficient and sustainable photovoltaic technologies

ITO Modification for Efficient Inverted Organic Solar Cells

We demonstrate a facile approach to designing transparent electron-collecting electrodes by depositing thin layers of medium and low work function metals on top of transparent conductive metal oxides (TCOs) such as ITO and FTO. The modified electrodes were fairly stable for months under ambient conditions and maintained their electrical characteristics. XPS spectroscopy data strongly suggested integration of the deposited metal in the TCO structure resulting in additional doping of the conducting oxide at the interface. Kelvin probe microscopy measurements revealed a significant decrease in the ITO work function after modification. Organic solar cells based on three different conjugated polymers have demonstrated state of the art performances in inverted device geometry using Mg- or Yb-modified ITO as electron collecting electrode. The simplicity of the proposed approach and the excellent ambient stability of the modified ITO electrodes allows one to expect their wide utilization in research laboratories and electronic industry

Water-Soluble Fullerene Derivatives as Brain Medicine: Surface Chemistry Determines If They Are Neuroprotective and Antitumor

Delivering drugs to the central nervous system (CNS) is a major challenge in treating CNS-related diseases. Nanoparticles that can cross blood–brain barrier (BBB) are potential tools. In this study, water-soluble C₆₀ fullerene derivatives with different types of linkages between the fullerene cage and the solubilizing addend were synthesized (compounds <b>1</b>–<b>3</b>: C–C bonds, compounds <b>4</b>–<b>5</b>: C–S bonds, compound <b>6</b>: C–P bonds, and compounds <b>7</b>–<b>9</b>: C–N bonds). Fullerene derivatives <b>1</b>–<b>6</b> were observed to induce neural stem cell (NSC) proliferation <i>in vitro</i> and rescue the function of injured CNS in zebrafish. Fullerene derivatives <b>7</b>–<b>9</b> were found to inhibit glioblastoma cell proliferation <i>in vitro</i> and reduce glioblastoma formation in zebrafish. These effects were correlated with the cell metabolic changes. Particularly, compound <b>3</b> bearing residues of phenylbutiryc acids significantly promoted NSC proliferation and neural repair without causing tumor growth. Meanwhile, compound <b>7</b> with phenylalanine appendages significantly inhibited glioblastoma growth without retarding the neural repair. We conclude that the surface functional group determines the properties as well as the interactions of C₆₀ with NSCs and glioma cells, producing either a neuroprotective or antitumor effect for possible treatment of CNS-related diseases

Highly Efficient All-Inorganic Planar Heterojunction Perovskite Solar Cells Produced by Thermal Coevaporation of CsI and PbI₂

We report here all inorganic CsPbI₃ planar junction perovskite solar cells fabricated by thermal coevaporation of CsI and PbI₂ precursors. The best devices delivered power conversion efficiency (PCE) of 9.3 to 10.5%, thus coming close to the reference MAPbI₃-based devices (PCE ≈ 12%). These results emphasize that all inorganic lead halide perovskites can successfully compete in terms of photovoltaic performance with the most widely used hybrid materials such as MAPbI₃

Design of (X-DADAD)_<i>n</i> Type Copolymers for Efficient Bulk Heterojunction Organic Solar Cells

We show that extended TBTBT structure (T = thiophene, B = benzothiadiazole) can be used as an electron-deficient building block for designing conjugated polymers with deeply lying HOMO energy levels and narrow band gaps. The first carbazole–TBTBT copolymer <b>P2</b> demonstrated power conversion efficiencies exceeding 6% in bulk heterojunction solar cells in combination with advanced operational stability, unlike conventional donor polymers such as PTB7, PBDTTT-CF, etc

Reversible and Irreversible Electric Field Induced Morphological and Interfacial Transformations of Hybrid Lead Iodide Perovskites

We report reversible and irreversible strain effects and interfacial atomic mixing in MAPbI₃/ITO under influence of external electric bias and photoillumination. Using conductive-probe atomic force microscopy, we locally applied a bias voltage between the MAPbI₃/ITO and the conductive tip and observed local dynamic strain effects and current under conditions of forward bias. We found that the reversible part of the strain is associated with a current spike at the current onset stage and can therefore be related to an electrochemical process accompanied by local molar volume change. Similar partly reversible surface deformation was observed when the tip–sample contact was illuminated by light. Time-of-flight secondary ion mass spectrometry of electrically biased regions revealed massive atomic mixing at the buried MAPbI₃/ITO interface, while the top MAPbI₃ surface, subjected to strong morphological damage at the tip–surface contact, revealed less significant chemical decomposition

Probing the Intrinsic Thermal and Photochemical Stability of Hybrid and Inorganic Lead Halide Perovskites

We report a careful and systematic study of thermal and photochemical degradation of a series of complex haloplumbates APbX₃ (X = I, Br) with hybrid organic (A⁺ = CH₃NH₃) and inorganic (A⁺ = Cs⁺) cations under anoxic conditions (i.e., without exposure to oxygen and moisture by testing in an inert glovebox environment). We show that the most common hybrid materials (e.g., MAPbI₃) are intrinsically unstable with respect to the heat- and light-induced stress and, therefore, can hardly sustain the real solar cell operation conditions. On the contrary, the cesium-based all-inorganic complex lead halides revealed far superior stability and, therefore, provide an impetus for creation of highly efficient and stable perovskite solar cells that can potentially achieve pragmatic operational benchmarks