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All-perovskite tandem solar cells (APTSCs) offer the potential to surpass the Shockley-Queisser limit of single-junction solar cells at low cost. However, high-performance APTSCs contain unstable methylammonium (MA) cation in the tin-lead (Sn-Pb) narrow bandgap subcells. Currently, MA-free Sn-Pb perovskite solar cells (PSCs) show lower performance compared with their MA-containing counterparts. This is due to the high trap density associated with Sn 2+ oxidation, which is exacerbated by the rapid crystallization of MA-free Sn-containing perovskite. Here, a multifunctional additive rubidium acetate (RbAC) is proposed to passivate Sn-Pb perovskite. We find that RbAC can suppress Sn 2+ oxidation, alleviate microstrain, and improve the crystallinity of the MA-free Sn-Pb perovskite. Consequently, the resultant Sn-Pb PSCs achieve a power conversion efficiency (PCE) of 23.02%, with an open circuit voltage ( V oc) of 0.897 V, and a filling factor (FF) of 80.64%, and more importantly the stability of the device is significantly improved. When further integrated with a 1.79-electron volt MA-free wide-bandgap PSC, a 29.33% (certified 28.11%) efficient MA-free APTSCs with a high V oc of 2.22 volts is achieved. The high trap density associated with tin (II) oxidation impacts the device performance of methylammonium cation-free tin-lead perovskite solar cells. Here, authors employ rubidium acetate for defect passivation and achieve efficient and stable single-junction and all-perovskite tandem solar cells.

The Qizhou Island sea area is located northeast of Hainan Island and is characterized by extensive and steep narrow continental shelves to the northeast and southwest, respectively, it is connected to the Qiongzhou Strait to the west. Its unique geographical location is important for investigating sediment distribution and transport patterns. The present study analyzed the grain size characteristics of 80 surface sediment samples from the Qizhou Island sea area, revealing that the northwest section is predominantly composed of clay, whereas the southeast section is primarily sandy. End-member modeling of grain size identified four distinct components: EM1 represents the offshore transport of terrestrial materials from the northwest, EM2 indicates material input from the southwest, EM3 reflects material input from the northeast, and EM4 may signify residual sediments from a previous low sea level period. Grain size trend analysis revealed that the northeastern area mainly receives material input from the northeast, while the southwestern region is dominated by input from the southwest. Numerical simulation experiments demonstrated that the predominant current direction in the study area is from northeast to southwest. The sedimentation model illustrated that sediment thickness decreases from the northeast to the southwest annually, aligning with material input from the northeast. However, sediment thickness in the southern region is greater between September and November, attributed to a shift in current direction to southwest-northeast during the summer monsoon, which transports substantial riverine sediments generated by summer monsoon and typhoon rainfall from Hainan Island into the study area. The bi-directional sediment transport in this region is driven by seasonal currents influenced by the East Asian monsoon and is further affected by river systems in Southern China and smaller mountainous rivers on Hainan Island. Further investigation involving additional indicators in this area is anticipated to enhance our comprehension of the source-sink system under the combined influence of major rivers and small mountainous rivers globally.