2D perovskite-stabilized FACsPbI 3 (FA = formamidinium) perovskite solar cells were fabricated in both normaltype and inverted-type architectures. While the normal-type devices exhibited a high power conversion efficiency of 20.2%, their reproducibility was limited. On the other hand, the inverted-type devices exhibited an efficiency of 18.2% with a greater stability and higher reproducibility than those of the normal-type devices. The reduced reproducibility of the normal-type devices was associated with the crack formation on the perovskite films during a spin-coating process. The hardness of both the perovskite and the sublayer was directly linked to the crack formation. Inverted-type 2D/3D FACsPbI 3 with ozone-treated poly(triarylamine) as sublayer exhibited the highest phase stability owing to the hydrophobic nature of poly(triarylamine) and improved energy level alignment upon an ozone treatment. In addition, strong interaction between phenethylamine cations of the 2D perovskite and of the 3D FACsPbI 3 crystal at grain boundaries contributed to the high phase stability.

Fullerene cations, namely [60]fullerene radical cation (C60˙+) and organo[60]fullerenyl cation (RC60+), are less investigated as intermediates in synthetic fullerene chemistry because of the intrinsic electronegativity of C60. Remarkably, these two intermediates can mediate reactions that afford versatile, unique and unexpected fullerene derivatives. This review article mainly describes these C60˙+ and RC60+ intermediates and includes a variety of topics, from the generation of C60˙+ and RC60+ species to their applications in fullerene modification reactions, such as Friedel-Crafts hydroarylation, nucleophilic addition, dimerization, intramolecular rearrangement reactions, and intramolecular cyclization reactions. Additionally, this review deeply discusses the mechanism of the formation of unique [60]fullerene derivatives involving [60]fullerene radical cation and organo[60]fullerenyl cation intermediates. In addition, the electrochemical properties and photovoltaic performance of these fullerene derivatives produced through C60˙+ or RC60+-mediated reactions are discussed in this review.

Fullerenes have attracted considerable interest as an electron-transporting layer in perovskite solar cells. Fullerene-based perovskite solar cells produce no hysteresis and do not require high-temperature annealing. However, high power conversion efficiency has been only achieved when the fullerene layer is thermally evaporated, which is an expensive process. In this work, the limitations of a solution-processed fullerene layer have been identified as high crystallinity and the presence of remnant solvents, in contrast to a thermally deposited C60 film, which has low crystallinity and no remaining solvents. As a solution to these problems, a mixed C60 and C70 solution-processed film, which exhibits low crystallinity, is proposed as an electron-transporting layer. The mixed-fullerene-based devices produce power conversion efficiencies as high as that of the thermally evaporated C60-based device (16.7%) owing to improved fill factor and open-circuit voltage. In addition, by vacuum-drying the mixed fullerene film, the power conversion efficiency of the solution-processed perovskite solar cells is further improved to 18.0%. This improvement originates from the enhanced transmittance and charge transport by removing the solvent effect. This simple and low-cost method can be easily used in any type of solar cells with fullerene as the electron-transporting layer.

Perovskite crystal grain size control, grain boundary passivation, and grain bridging are the keys to obtaining high efficiency in perovskite solar cells. A small amount of semiconducting single-walled carbon nanotubes added to a perovskite active layer can achieve this. In particular, the surfactants attached to the semiconducting single-walled carbon nanotubes a crucial role. In this work, we synthesized a new surfactant, 4,6-di­(anthracen-9-yl)-1,3-phenylene bis­(dimethylcarbamate), which has a polyaromatic group on one end and a urea-analogue carbamate group on the other end. The polyaromatic anthracene end functions as a nanotweezer clenching the carbon nanotubes strongly via π–π interaction while the carbamate end interacts with Pb2+, functioning as a strong Lewis base. In addition, the new surfactant has conjugated double bonds with a suitable bandgap, resulting in enhanced charge mobility in the perovskite film. Overall, the new surfactant-clenched semiconducting carbon nanotubes showcase superior effectiveness as passivators and charge bridges in perovskite solar cells as compared to the conventional deoxycholate surfactant-wrapped semiconducting single-walled carbon nanotubes. The new surfactant-attached semiconducting carbon nanotube-added NH3CH3PbI3-based perovskite solar cells exhibited a power conversion efficiency of 20.7%, which is higher than that of the reference devices with no additives (18.4%) and the previously reported semiconducting single-walled carbon nanotube-added devices (19.7% in this work and 19.5% in the literature).

Intake of fermented soy milk significantly improved the ecosystem of the intestinal tract in the body by increasing the amount of probiotics.