γ-Ray Irradiation Enables Annealing- and Light-Soaking-Free Solution Processable SnO2 Electron Transport Layer for Inverted Organic Solar Cells.

The electrode buffer layer is crucial for high-performance and stable OSCs, optimizing charge transport and energy level alignment at the interface between the polymer active layer and electrode. Recently, SnO2 has emerged as a promising material for the cathode buffer layer due to its desirable properties, such as high electron mobility, transparency, and stability. Typically, SnO2 nanoparticle layers require a postannealing treatment above 150°C in an air environment to remove the surfactant ligands and obtain high-quality thin films. However, this poses challenges for flexible electronics as flexible substrates can't tolerate temperatures exceeding 100°C. This study presents solution-processable and annealing-free SnO2 nanoparticles by employing y-ray irradiation to disrupt the bonding between surfactant ligands and SnO2 nanoparticles. The SnO2 layer treated with y-ray irradiation is used as an electron transport layer in OSCs based on PTB7-Th:IEICO-4F. Compared to the conventional SnO2 nanoparticles that required high-temperature annealing, the y-SnO2 nanoparticle-based devices exhibit an 11% comparable efficiency without postannealing at a high temperature. Additionally, y-ray treatment has been observed to eliminate the light-soaking effect of SnO2 . By eliminating the high-temperature postannealing and light-soaking effect, y-SnO2 nanoparticles offer a promising, cost-effective solution for future flexible solar cells fabricated using roll-to-roll mass processing.

Inverted Polymer Solar Cells with Annealing-Free Solution-Processable NiO.

Nickel oxide (NiO) offers intrinsic p-type behavior and high thermal and chemical stability, making it promising as a hole transport layer (HTL) material in inverted organic solar cells. However, its use in this application has been rare because of a wettability problem caused by use of water as base solvent and high-temperature annealing requirements. In the present work, an annealing-free solution-processable method for NiO deposition is developed and applied in both conventional and inverted non-fullerene polymer solar cells. To overcome the wettability problem, the typical DI water solvent is replaced with a mixed solvent of DI water and isopropyl alcohol with a small amount of 2-butanol additive. This allows a NiO nanoparticle suspension (s-NiO) to be deposited on a hydrophobic active layer surface. An inverted non-fullerene solar cell based on a blend of p-type polymer PTB7-Th and non-fullerene acceptor IEICO-4F exhibits the high efficiency of 11.23% with an s-NiO HTL, comparable to the efficiency of an inverted solar cell with a MoOx HTL deposited by thermal evaporation. Conventionally structured devices including this s-NiO layer show efficiency comparable to that of a conventional device with a PEDOT:PSS HTL.

An Efficient Green Approach to Constructing Adenine Sulfate-Derived Multicolor Sulfur- and Nitrogen-Codoped Carbon Dots and Their Bioimaging Applications.

A cost-effective and environmentally friendly approach is proposed for producing N- and S-codoped multicolor-emission carbon dots (N- and S-codoped MCDs) at a mild reaction temperature (150 °C) and relatively short time (3 h). In this process, adenine sulfate acts as a novel precursor and doping agent, effectively reacting with other reagents such as citric acid, para-aminosalicylic acid, and ortho-phenylenediamine, even during solvent-free pyrolysis. The distinctive structures of reagents lead to the increased amount of graphitic nitrogen and sulfur doping in the N- and S-codoped MCDs. Notably, the obtained N- and S-codoped MCDs exhibit considerable fluorescence intensities, and their emission color can be adjusted from blue to yellow. The observed tunable photoluminescence can be attributed to variations in the surface state and the amount of N and S contents. Furthermore, due to the favorable optical properties, good water solubility and biocompatibility, and low cytotoxicity, these N- and S-codoped MCDs, especially green carbon dots, are successfully applied as fluorescent probes for bioimaging. The affordable and environmentally friendly synthesis method employed to create N- and S-codoped MCDs, combined with their remarkable optical properties, offers a promising avenue for their use in various fields, particularly in biomedical applications.

17% Non-Fullerene Organic Solar Cells with Annealing-Free Aqueous MoO x.

A charge transport layer based on transition metal-oxides prepared by an anhydrous sol-gel method normally requires high-temperature annealing to achieve the desired quality. Although annealing is not a difficult process in the laboratory, it is definitely not a simple process in mass production, such as roll-to-roll, because of the inevitable long cooling step that follows. Therefore, the development of an annealing-free solution-processable metal-oxide is essential for the large-scale commercialization. In this work, a room-temperature processable annealing-free "aqueous" MoO x solution is developed and applied in non-fullerene PBDB-T-2F:Y6 solar cells. By adjusting the concentration of water in the sol-gel route, an annealing-free MoO x with excellent electrical properties is successfully developed. The PBDB-T-2F:Y6 solar cell with the general MoO x prepared by the anhydrous sol-gel method shows a low efficiency of 7.7% without annealing. If this anhydrous MoO x is annealed at 200 °C, the efficiency is recovered to 17.1%, which is a normal value typically observed in conventional structure PBDB-T-2F:Y6 solar cells. However, without any annealing process, the solar cell with aqueous MoO x exhibits comparable performance of 17.0%. In addition, the solar cell with annealing-free aqueous MoO x exhibits better performance and stability without high-temperature annealing compared to the solar cells with PEDOT:PSS.