Artificial Intelligence-Based, Wavelet-Aided Prediction of Long-Term Outdoor Performance of Perovskite Solar Cells.

The commercial development of perovskite solar cells (PSCs) has been significantly delayed by the constraint of performing time-consuming degradation studies under real outdoor conditions. These are necessary steps to determine the device lifetime, an area where PSCs traditionally suffer. In this work, we demonstrate that the outdoor degradation behavior of PSCs can be predicted by employing accelerated indoor stability analyses.

Soil adsorption and transport of lead in the presence of perovskite solar cell-derived organic cations.

Perovskite photovoltaics offer a highly efficient and low-cost solar energy harvesting technology. However, the presence of lead (Pb) cations in photovoltaic halide perovskite (HaPs) materials is concerning, and quantifying the environmental hazard of accidental Pb leaching into the soil is crucial for assessing the sustainability of this technology. Pb from inorganic salts was previously found to remain in the upper soil layers due to adsorption.

Advanced Nonvolatile Organic Optical Memory Using Self-Assembled Monolayers of Porphyrin-Fullerene Dyads.

Photo-switchable organic field-effect transistors (OFETs) represent an important platform for designing memory devices for a diverse array of products including security (brand-protection, copy-protection, keyless entry, etc.), credit cards, tickets, and multiple wearable organic electronics applications. Herein, we present a new concept by introducing self-assembled monolayers of donor-acceptor porphyrin-fullerene dyads as light-responsive triggers modulating the electrical characteristics of OFETs and thus pave the way to the development of advanced nonvolatile optical memory.

Hybrid organic nanocrystal/carbon nanotube film electrodes for air- and photo-stable perovskite photovoltaics.

We report on utilizing free-standing hybrid perylenediimide/carbon nanotube (PDI/CNT) films fabricated in air as back contacts for fully inorganic perovskite solar cells (glass/FTO/dense TiO2/mesoporous TiO2/CsPbBr3/back electrode). The back contact electrode connection is performed by film transfer rather than by vacuum deposition or by wet processing, allowing the formation of highly homogeneous contacts under ambient conditions. The use of this novel electrode in solar cells based on CsPbBr3 resulted in efficiency of 5.

Two-site HO photo-oxidation on haematite photoanodes.

HO is a sacrificial reductant that is often used as a hole scavenger to gain insight into photoanode properties. Here we show a distinct mechanism of HO photo-oxidation on haematite (α-FeO) photoanodes. We found that the photocurrent voltammograms display non-monotonous behaviour upon varying the HO concentration, which is not in accord with a linear surface reaction mechanism that involves a single reaction site as in Eley-Rideal reactions.

UV-Cross-linkable Donor-Acceptor Polymers Bearing a Photostable Conjugated Backbone for Efficient and Stable Organic Photovoltaics.

High-performance photovoltaic polymers bearing cross-linkable function together with a photorobust conjugated backbone are highly desirable for organic solar cells to achieve both high device efficiency and long-term stability. In this study, a family of such polymers is reported based on poly[(2,5-bis(2-hexyldecyloxy)phenylene)- alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[ c]-[1,2,5]thiadiazole)] (PPDT2FBT), a high-performance photovoltaic donor-acceptor polymer, with different contents of terminal vinyl-appended side chains for cross-linking. The polymers were named PPDT2FBT-V and prepared by varying the feeding ratio ( x mol %, x = 0, 5, 10, and 15) of the vinyl-appended monomer in polymerization.

Concentrated Sunlight for Materials Synthesis and Diagnostics.

Herein, the use of highly concentrated sunlight for materials science research is reviewed. Specific research directions include: (1) the generation of inorganic nanostructures, some of which had eluded experimental realization with conventional synthetic processes, and (2) elucidating the processes governing the degradation of organic and perovskite-based photovoltaic materials and devices, along with accelerated assessment of their stability. Both approaches employ solar concentrators capable of producing flux densities exceeding those of terrestrial solar radiation by up to three orders of magnitude, and are geared toward either creating extensive ultrahot reactor conditions conducive to the rapid, safe synthesis of unusual nanomaterials or judiciously interrogating photovoltaic devices.

Role of oxygen functional groups in reduced graphene oxide for lubrication.

Functionalized and fully characterized graphene-based lubricant additives are potential 2D materials for energy-efficient tribological applications in machine elements, especially at macroscopic contacts. Two different reduced graphene oxide (rGO) derivatives, terminated by hydroxyl and epoxy-hydroxyl groups, were prepared and blended with two different molecular weights of polyethylene glycol (PEG) for tribological investigation. Epoxy-hydroxyl-terminated rGO dispersed in PEG showed significantly smaller values of the friction coefficient.

Effect of Halide Composition on the Photochemical Stability of Perovskite Photovoltaic Materials.

The photochemical stability of encapsulated films of mixed halide perovskites with a range of MAPb(I Br ) (MA=methylammonium) compositions (solid solutions) was investigated under accelerated stressing using concentrated sunlight. The relevance of accelerated testing to standard operational conditions of solar cells was confirmed by comparison to degradation experiments under outdoor sunlight exposure. We found that MAPbBr films exhibited no degradation, while MAPbI and mixed halide MAPb(I Br ) films decomposed yielding crystallization of inorganic PbI accompanied by degradation of the perovskite solar light absorption, with faster absorption degradation in mixed halide films.

Temperature- and Component-Dependent Degradation of Perovskite Photovoltaic Materials under Concentrated Sunlight.

We report on accelerated degradation testing of MAPbX3 films (X = I or Br) by exposure to concentrated sunlight of 100 suns and show that the evolution of light absorption and the corresponding structural modifications are dependent on the type of halide ion and the exposure temperature. One hour of such exposure provides a photon dose equivalent to that of one sun exposure for 100 hours. The degradation in absorption of MAPbI3 films after exposure to 100 suns for 60 min at elevated sample temperature (∼45-55 °C), due to decomposition of the hybrid perovskite material, is documented.

Photocurrent of a single photosynthetic protein.

Photosynthesis is used by plants, algae and bacteria to convert solar energy into stable chemical energy. The initial stages of this process--where light is absorbed and energy and electrons are transferred--are mediated by reaction centres composed of chlorophyll and carotenoid complexes. It has been previously shown that single small molecules can be used as functional components in electric and optoelectronic circuits, but it has proved difficult to control and probe individual molecules for photovoltaic and photoelectrochemical applications.

Conductance of a biomolecular wire.

Carotenoids (Car) act as "wires" that discharge unwanted electrons in the reaction center of higher plants. One step in this "side-path" electron conduction is thought to be mediated by Car oxidation. We have carried out direct measurements of the conductance of single-Car molecules under potential control in a membrane-mimicking environment, and we found that when Car are oxidized conductance is enhanced and the electronic decay constant (beta) is decreased.

Molecular adsorption-mediated control over the electrical characteristics of polycrystalline CdTe/CdS solar cells.

The effect of surface treatments on p-CdTe/n-CdS solar cell performance was examined. Adsorption of organic molecules with various magnitudes and directions of the dipole moment on p-CdTe resulted in controlled changes in electron affinity and surface bond bending. Similar adsorption on CdTe in state-of-the-art p-CdTe/n-CdS solar cells changes the cell performance, and we explain this by a combination of increased series resistance and changes in light absorption and in cell photovoltage.