[en] Perovskite solar cells (PSCs) have become a promising candidate for the next-generation photovoltaic technologies. As an essential element for high-efficiency PSCs however, the heavy metal Pb is soluble in water, causing a serious threat to the environment and human health. Due to the weak ionic bonding in three-dimensional (3D) perovskites, drastic structure decomposition occurs when immersing the perovskite film in water, which accelerates the Pb leakage. By introducing the chemically stable Dion-Jacobson (DJ) 2D perovskite at the 3D perovskite surface, the film dissolution is significantly slowed down, which retards lead leakage. As a result, the Pb contamination is dramatically reduced under various extreme conditions. In addition, the PSCs device deliver a power conversion efficiency (PCE) of 23.6 % and retain over 95 % of their initial PCE after the maximum power point tracking for over 1100 h. (© 2022 Wiley‐VCH GmbH)

[en] The phenomenological study of evolving galaxy populations in Peng et al. has shown that star forming galaxies can be quenched by two distinct processes: mass quenching and environment quenching. To explore the mass quenching process in local galaxies, we study the massive central disk galaxies with stellar mass above the Schechter characteristic mass. In Zhang et al., we showed that during the quenching of the massive central disk galaxies as their star formation rate decreases, their molecular gas mass and star formation efficiency drop rapidly but their H i gas mass remains surprisingly constant. To identify the underlying physical mechanisms, in this work we analyze the change during quenching of various structure parameters, bar frequency, and active galactic nucleus (AGN) activity. We find three closely related facts. On average, as star formation rate decreases in these galaxies: (1) they become progressively more compact, indicated by their significantly increasing concentration index, bulge-to-total mass ratio, and central velocity dispersion, which are mainly driven by the growth and compaction of their bulge component; (2) the frequency of barred galaxies increases dramatically, and at a given concentration index the barred galaxies have a significantly higher quiescent fraction than unbarred galaxies, implying that the galactic bar may play an important role in mass quenching; and (3) the “AGN” frequency increases dramatically from 10% on the main sequence to almost 100% for the most quiescent galaxies, which is mainly driven by the sharp increase of LINERs. These observational results lead to a self-consistent picture of how mass quenching operates.

[en] Star formation and quenching are two of the most important processes in galaxy formation and evolution. We explore in the local universe the interrelationships among key integrated galaxy properties, including stellar mass M _*, star formation rate (SFR), specific SFR (sSFR), molecular gas mass $M_{{\mathrm{H}}_2}$, star formation efficiency (SFE) of the molecular gas, and the molecular gas to stellar mass ratio μ. We aim to identify the most fundamental scaling relations among these key galaxy properties and their interrelationships. We show that the integrated $M_{{\mathrm{H}}_2}$–SFR, SFR–M _*, and $M_{{\mathrm{H}}_2}$–M _* relations can be simply transformed from the μ–sSFR, SFE–μ, and SFE–sSFR relations, respectively. The transformation, in principle, can increase or decrease the scatter of each relation. Interestingly, we find that the latter three relations all have significantly smaller scatter than the corresponding former three. We show that the probability to achieve the observed small scatter by accident is extremely close to zero. This suggests that the smaller scatters of the latter three relations are driven by a more universal physical connection among these quantities. We then show that the large scatters in the former relations are due to their systematic dependence on other galaxy properties, and on the star formation and quenching process. We propose the sSFR–μ–SFE relation as the fundamental formation relation (FFR), which governs the star formation and quenching process and provides a simple framework to study galaxy evolution. Other scaling relations, including the integrated Kennicutt–Schmidt law, star-forming main sequence, and molecular gas main sequence, can all be derived from the FFR.

[en] In Dou et al., we introduced the fundamental formation relation (FFR), a tight relation between specific star formation rate (sSFR), H₂ star formation efficiency (SFE${}_{{\mathrm{H}}_2}$), and the ratio of H₂ to stellar mass. Here, we show that atomic gas H ɪ does not follow a similar FFR as H₂. The relation between SFE_Hɪ and sSFR shows significant scatter and strong systematic dependence on all of the key galaxy properties that we have explored. The dramatic difference between H ɪ and H₂ indicates that different processes (e.g., quenching by different mechanisms) may have very different effects on H ɪ in different galaxies and hence produce different SFE_Hɪ–sSFR relations, while the SFE${}_{{\mathrm{H}}_2}$–sSFR relation remains unaffected. The fact that the SFE${}_{{\mathrm{H}}_2}$–sSFR relation is independent of other key galaxy properties, and that sSFR is directly related to the cosmic time and acts as the cosmic clock, make it natural and very simple to study how different galaxy populations (with different properties and undergoing different processes) evolve on the same SFE${}_{{\mathrm{H}}_2}$–sSFR ∼ t relation. In the gas regulator model (GRM), the evolution of a galaxy on the SFE${}_{{\mathrm{H}}_2}$–sSFR(t) relation is uniquely set by a single mass-loading parameter ${\mathrm{\lambda <!--\; ??\; -->}}_{\mathrm{n}\mathrm{e}\mathrm{t},{\mathrm{H}}_2}$. This simplicity allows us to accurately derive the H₂ supply and removal rates of the local galaxy populations with different stellar masses, from star-forming galaxies to the galaxies in the process of being quenched. This combination of FFR and GRM, together with the stellar metallicity requirement, provide a new powerful tool to study galaxy formation and evolution.