We prepared rhombohedral and cubic KBiS 2 thin films under mild conditions and demonstrated the formation of oxygen centered radicals along with an excellent charge carrier lifetime upon irradiation.

Electron transfer through molecular wires underpins numerous research fields, ranging from single-molecule electronics to fundamental biological processes and their application in (bio)electrocatalysis. Here we report a series of 1-3-nm-long ferrocene-terminated conjugated molecular wires, anchored to indium tin oxide electrodes, that exhibit an electron transfer mechanism dominated by hopping (with a β value of 0.043 Å-1). We show that the nature of the electrode, namely the small energy gap between the electron donor and acceptor, explains the unexpected electron transfer mechanism in these short wires. We demonstrate the applicability of these anchored molecular wires as the hole-extraction layer in a tin perovskite solar cell. We show improved performance in devices employing these molecular wires compared with the more conventional hole-extraction layers typically used in tin perovskite solar cells. This work not only opens avenues for mechanistic investigations of interfacial electron transfer using molecular wires but also showcases their potential impact in applications such as photovoltaics.

The generation of free carriers through doping is essential for transforming the electronic properties of organic semiconductors (OSCs). We show that metallocenium salts facilitate OSC doping, enabling high-performance perovskite solar cells.

Controlled doping of organic semiconductors is crucial for their application in optoelectronic devices. In perovskite solar cells (PSCs), breakthrough efficiencies have relied on doped Spiro-OMeTAD hole transport materials. However, the ubiquitous adoption of multicomponent lithium-based doping schemes, known for their hygroscopic, volatile, and temperamental nature, remains a major issue for n-i-p PSCs. Therefore, next-generation dopants must be re-engineered from first principles. Here, we report a class of tailored ferrocenium oxidants as high-performance, comprehensive Spiro-OMeTAD dopants. Tuning ferrocenium reduction potentials enables near-quantitative Spiro-OMeTAD & sdot;+ conversion, affording optimal electronic and energetic properties. The resulting ferrocenium-doped PSCs outperform conventional counterparts, achieving device and module efficiencies of 26.13% and 22.21%, respectively, with ultra-low dopant loadings. Devices show excellent operational stability, retaining 95% (unheated) and 87% (held at 65 degrees C) of the initial efficiency after 1,000 h of continuous operation. Our results reveal the unrecognized potential of comprehensive doping paradigms in PSCs and beyond.

The incorporation of guanidinium (Gua) cations has significantly enhanced the optoelectronic properties of various perovskite compositions. When combined with other A-site cations in perovskite solar cells (PSCs), Gua cations not only enhance the power conversion efficiency of the solar cells but often improve their overall stability. While most studies examining the impact of Gua focus on PSCs with the n-i-p (conventional) structure, fewer have investigated its effects on the mechanism and performance of the p-i-n (inverted) structure. We investigate how partially substituting A-site cations with Gua affects the performance of PSCs and the associated charge carrier dynamics. Enhanced performance is observed in Gua-substituted inverted PSCs, primarily due to improved short-circuit current density and fill factor values. Our spectroscopic and microscopic analyses reveal that these enhancements stem from accelerated charge transport within the perovskite layer combined with inhibited ion migration following Gua incorporation, attributed to the reduction of localized inhomogeneities, which also notably enhance device stability. Our findings elucidate the role of Gua in inverted PSCs, showing negligible impact on open-circuit voltage but significant improvement in charge extraction efficiency. This contrasts with previous reports on conventional structures, where performance enhancement is primarily attributed to trap state reduction, resulting in higher open-circuit voltage.

Tin perovskite solar cells (Sn-PSCs) have emerged as excellent candidates for nontoxic narrow bandgap PSCs. Nevertheless, the technology remains limited by both stability and suboptimal energetic alignment with conventional charge transport layers. Compositional tuning is central to high-performance Sn-PSCs, replacing substoichiometric iodide ions with bromide. However, incorporating SnBr2 as the bromide source introduces SnBr4 impurities, underscoring the need to understand the consequences of SnBr4 on both performance and degradation chemistry. Presently, the absence of such understanding has engendered a reliance on organobromide salts, neglecting a critical opportunity to enhance stability via the reduction of unstable SnI2. Herein, the influence of SnBr4 impurities on the structural, optoelectronic, and electronic properties of Sn-perovskites is investigated. Removal of SnBr4 impurities from SnBr2 results in drastically improved morphology, a 40% lower trap density and enhanced device performance of 150%. Furthermore, both the fundamental chemistry and degradation pathways in SnI4 and SnBr4 are compared, demonstrating the latter does not decompose to the molecular halogen-a key weakness of iodine-based Sn-PSCs. The present findings offer critical chemical and electronic insights into the presence of SnBr4, the importance of its removal and the opportunities afforded by using SnBr2 to minimize unstable SnI2 in Br-rich Sn-perovskite phases.

Antisolvent treatment is used in the fabrication of perovskite films to control grain growth during spin coating. We study widely incorporated aromatic hydrocarbons and aprotic ethers, discussing the origin of their performance differences in 2D/3D Sn perovskite (PEA0.2FA0.8SnI3) solar cells. Among the antisolvents that we screen, diisopropyl ether yields the highest power conversion efficiency in solar cells. We use a combination of optical and structural characterization techniques to reveal that this improved performance originates from a higher concentration of 2D phase, distributed evenly throughout the 2D/3D Sn perovskite film, leading to better crystallinity. This redistribution of the 2D phase, as a result of diisopropyl ether antisolvent treatment, has the combined effect of decreasing the Sn4+ defect density and background hole density, leading to devices with improved open-circuit voltage, short-circuit current, and power conversion efficiency.