A first-principles study of organic Lewis bases for passivating tin-based perovskite solar cells.

Tin-based perovskite solar cells (PSCs) are potential light absorbers for solar cell applications since they are less toxic compared to commonly used lead-based alternatives. Retaining the less stable Sn2+ state is key to improving the efficiency of tin-based PSCs. Organic Lewis base molecules have demonstrated potential to achieve this purpose. However, the critical factors influencing the performance of Lewis bases are largely unknown. In this study, we applied density functional theory (DFT) to investigate seven Lewis base materials, including methanol (MeOH), dimethyl ether (DME), ethyl methyl ether (EME), methyl acetate (MeOAc), methyl ammonium (MA), methyl sulfonic acid (MSA), and methyl phosphonic acid (MPA). Our results show that the effectiveness of passivation is linked to the gap between the HOMO and the LUMO (Egap). These findings provide theoretical guidance to screen Lewis base additives for enhancing energy conversion efficiencies of tin-based PSCs.

First-principles prediction of one-dimensional conductive metallic organic polymers as ultrahigh energy density anode for lithium-ion batteries.

Metal-Organic Polymers (MOPs) have attracted growing attention for lithium-ion battery (LIB) applications due to their merits in orderly ionic transportation and robust structure stability in electrochemical reactions. However, they suffer from poor electronic conductivity. In this work, we apply first-principles density functional theory to explore the potential of three one-dimensional (1D) electrically conductive C6H2S4TM (TM = Fe, Co, and Ni) MOPs with the π-d conjugated coordination as anode materials for Li+ ions storage. Our theoretical results reveal that these 1D MOPs possess a superior theoretical capacity of over 748 mA h g-1. In particular, the 1D C6H2S4Ni MOP shows an exceptional theoretical specific capacity of 1110 mA h g-1 based on the three-electron transferring reaction, which significantly outperforms the traditional graphite-based anode material in LIBs. Moreover, the resonant charge transfer between Ni metal and ligand within the 1D C6H2S4Ni MOP reduces the diffusion energy barrier of the Li atoms when they migrate on the surface of the MOP. The ultrahigh theoretical specific capacity of the C6H2S4Ni MOP predicts that it can be a promising anode material for LIBs.

Defect engineering of 1T'MX2(M= Mo, W andX= S, Se) transition metal dichalcogenide-based electrocatalyst for alkaline hydrogen evolution reaction.

The alkaline electrolyzer (AEL) is a promising device for green hydrogen production. However, their energy conversion efficiency is currently limited by the low performance of the electrocatalysts for the hydrogen evolution reaction (HER). As such, the electrocatalyst design for the high-performance HER becomes essential for the advancement of AELs. In this work, we used both hydrogen (H) and hydroxyl (OH) adsorption Gibbs free energy changes as the descriptors to investigate the catalytic HER performance of 1T' transition metal dichalcogenides (TMDs) in an alkaline solution. Our results reveal that the pristine sulfides showed better alkaline HER performance than their selenide counterparts. However, the activities of all pristine 1T' TMDs are too low to dissociate water. To improve the performance of these materials, defect engineering techniques were used to design TMD-based electrocatalysts for effective HER activity. Our density functional theory results demonstrate that introducing single S/Se vacancy defects can improve the reactivities of TMD materials. Yet, the desorption of OH becomes the rate-determining step. Doping defective MoS2with late 3d transition metal (TM) atoms, especially Cu, Ni, and Co, can regulate the reactivity of active sites for optimal OH desorption. As a result, the TM-doped defective 1T' MoS2can significantly enhance the alkaline HER performance. These findings highlight the potential of defect engineering technologies for the design of TMD-based alkaline HER electrocatalysts.