Photochemical Formation of C₁–C₅ Alkyl Nitrates in Suburban Hong Kong and over the South China Sea

Alkyl nitrates (RONO₂) are important reservoirs of atmospheric nitrogen, regulating nitrogen cycling and ozone (O₃) formation. In this study, we found that propane and <i>n</i>-butane were significantly lower at the offshore site (WSI) in Hong Kong (<i>p</i> < 0.05), whereas C₃–C₄ RONO₂ were comparable to the suburban site (TC) (<i>p</i> > 0.05). Stronger oxidative capacity at WSI led to more efficient RONO₂ formation. Relative incremental reactivity (RIR) was for the first time used to evaluate RONO₂–precursor relationships. In contrast to a consistently volatile organic compounds (VOC)-limited regime at TC, RONO₂ formation at WSI switched from VOC-limited regime during O₃ episodes to VOC and nitrogen oxides (NO_<i>x</i>) colimited regime during nonepisodes. Furthermore, unlike the predominant contributions of parent hydrocarbons to C₄–C₅ RONO₂, the production of C₁–C₃ RONO₂ was more sensitive to other VOCs like aromatics and carbonyls, which accounted for ∼40–90% of the productions of C₁–C₃ alkylperoxy (RO₂) and alkoxy radicals (RO) at both sites. This resulted from the decomposition of larger RO₂/RO and the change of OH abundance under the photochemistry of other VOCs. This study advanced our understanding of the photochemical formation of RONO₂, particularly the relationships between RONO₂ and their precursors, which were not confined to the parent hydrocarbons

All-Perovskite Tandems Enabled by Surface Anchoring of Long-Chain Amphiphilic Ligands

Perovskite solar cells (PSCs) in the pin structure are limited by nonradiative recombination at the electron transport layer (ETL) interface, which is exacerbated in narrow-bandgap (∼1.2 eV) Pb–Sn PSCs due to surface Sn oxidation and detrimental p-doping. Photoluminescence quantum yield studies herein indicated that ethane-1,2-diammonium (EDA) passivation only partially alleviates perovskite/ETL energetic losses. We pursued passivation of the defect-rich perovskite:ETL interface to reduce nonradiative losses; our target was to combine chemical coordination of Sn sites with the introduction of an interlayer, which we implemented by introducing long-chain carboxylic acid ligands at the perovskite surface. Treatment with oleic acid (OA) led to reduced recombination at the perovskite/ETL interface and evidence of Sn2+ coordination. This reduced the VOC deficit of Pb–Sn PSCs to 0.34 V, resulting in a 0.89 V VOC and PCE of 23.0% (22.4% stabilized). Incorporating the OA-treated Pb–Sn layer into a monolithic all-perovskite tandem, we report a 27.3% PCE (26.4% certified) and a VOC of 2.21 V