Tin−lead (Sn−Pb) alloyed perovskites are promising candidates for next-generation photovoltaics due to their appropriate bandgaps for multijunction tandem solar cells, which can potentially overcome the Shockley-Queisser limit. However, their power conversion efficiency (PCE) and stability are still impeded by the poor absorber quality and defects caused by the oxidation of Sn 2+ . Here, we introduced trimethylsulfoxonium iodide (TMSI) as an additive along with SnF 2 to fabricate Sn−Pb perovskite films with enlarged grains and improved film quality. TMSI restrained the oxidation of Sn 2+ through molecular interactions, reducing the formation of detrimental Sn vacancies. As a result, a highly oriented Sn−Pb alloyed perovskite with a lower defect density was obtained, along with suppressed ion migration. The TMSI-treated Sn−Pb-based devices exhibited a champion PCE of 22.6% and outstanding stability, retaining 83% of their original efficiency after 6000 h of storage under a N 2 atmosphere and maintaining 88% of their initial value after 1200 h of continuous one-sun illumination.

Shallow- and/or deep-level defects on perovskite surfaces and at grain boundaries serving as recombination centers can negatively affect photovoltaic device performance and stability, thus they need to be minimized. In this study, we modified perovskite films with furan-2,5-dicarboxylic acid (FDCA) to modulate perovskite crystallization and passivate multiple intrinsic shallow- and deep-level defects using an antisolvent method. Characterizations and density functional theory simulation were performed to investigate the coordination and hydrogen bonding interactions between FDCA and perovskite that led to oriented grains and reduced defects. The interactions between FDCA and perovskite reduced non-radiative recombination and improved charge transport. The FDCA-based solar cells exhibited a superior power conversion efficiency of over 24% with improved operation and storage stabilities. This passivation strategy reveals the mechanism behind the improvement of device performance.

Electrocatalytic promotion of water splitting is considered an effective way to obtain hydrogen, but it is limited by the expensive nature and scarcity of effective catalysts currently available. Due to their stability, efficient characteristics, and high activity, transition metal phosphides have attracted extensive attention from researchers in electrocatalysis. In this study, the effect of doping with group VIII elements on the hydrogen evolution reaction (HER) activity of CoP (011) was investigated using first-principles calculations based on density functional theory. More active sites were exposed by doping with Rh, Ir, Ni, Pd, and Pt atoms, which significantly improved the catalytic activity of CoP (011) for the HER. It has also been verified by the analysis of the crystal orbital Hamilton population and d-band centers, which indicated the electronic properties resulting in the HER activity improvement. Hydroxylation usually occurs on surfaces lacking coordination in a solution environment, influencing the active sites. Calculations show that adopting suitable transition-element doping can reduce the hydroxyl coverage on the (011) surface of cobalt phosphide and thus improve the HER efficiency. Since surface oxidation is inevitable in the oxygen evolution reaction (OER) process, one case was assumed that all Co atoms in the typical CoP (011) facet were oxidized to form CoOOH, which was studied to explore the mechanism of OER activity. The results indicated that surface oxidation could reduce the OER overpotential, which was the key for CoP to achieve a high-efficiency OER. The theoretical investigations presented that the substitution doping of Fe, Rh, and Ir activated the Co atom adjacent to the dopant atom, which significantly improved performance by adjusting the electronic structure. This theoretical investigation helps to understand the effects of doping and surface oxidation on the electrocatalytic activity of phosphides, and this provides a theoretical perspective basis for the design of transition metal-doped catalysts for overall water splitting.

Clean energy hydrogen, which can be produced by catalytic water splitting, has attracted more and more attention of researchers. Due to their low cost, abundance, and high efficiency, Transition metal phosphides (TMPs) have received more and more attention as ever-evolving catalytic materials instead of noble metal catalysts. In this work, The Cobalt hydroxide precursor was first grown on foam nickel (NF) by hydrothermal reaction, which was phosphated to Co2P though high temperature vapor phase. Then a small amount of Pt was anchored on the surface of Co2P, marked as Pt-Co2P/NF, by potential-cycling method. Both electrochemically active surface area (ECSA) and intrinsic catalytic activities of the catalyst were improved, with the performance of hydrogen evolution reaction (HER) increasing. The electrochemical test indicated that the Pt-Co2P/NF exhibited excellent electrocatalytic performance in alkaline electrolyte, and the overpotential was only 13mV and 133mV respectively at 10 and 1000 mA cm-2. The low Tafel slope of 28 mV dec−1 implied its rapid HER kinetics. Especially at high current density, Pt-Co2P/NF showed excellent catalytic activity and stability, which was possible to meet the requirements of hydrogen production industry. Coupled by first principle calculations based on density functional theory (DFT), a mechanism insight of the chemical transformation was provided, which could elucidate the origin of the platinum-sensitized behavior of HER.

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