Polymerization sites of small molecule acceptors (SMAs) play vital roles in determining device performance of all-polymer solar cells (all-PSCs). Different from our recent work about fluoro-and bromo-co-modified end group of IC-FBr (a mixture of IC-FBr1 and IC-FBr2), in this paper,w e synthesized and purified two regiospecific fluoro-and bromosubstituted end groups (IC-FBr-o &I C-FBr-m), which were then employed to construct two regio-regular polymer acceptors named PYF-T-o and PYF-T-m, respectively.Incomparison with its isomeric counterparts named PYF-T-m with different conjugated coupling sites,P YF-T-o exhibits stronger and bathochromic absorption to achieve better photon harvesting. Meanwhile,PYF-T-o adopts more ordered inter-chain packing and suitable phase separation after blending with the donor polymer PM6, which resulted in suppressed charge recombination and efficient charge transport. Strikingly,w eo bserved ad ramatic performance difference between the two isomeric polymer acceptors PYF-T-o and PYF-T-m. While devices based on PM6:PYF-T-o can yield power conversion efficiency (PCE) of 15.2 %, devices based on PM6:PYF-T-m only show poor efficiencies of 1.4 %. This work demonstrates the success of configuration-unique fluorinated end groups in designing high-performance regular polymer acceptors,w hich provides guidelines towardsdeveloping all-PSCs with better efficiencies.

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Nitrous acid (HONO) is one of the most important photochemical precursors of the hydroxyl radical in the sunlit urban atmosphere. The sources of HONO, however, are still poorly characterized, yet there is a disagreement between the field observations and the model results. Here, we show that light-induced NO2 heterogeneous chemistry on authentic urban grime can make an important contribution to the total HONO levels in the urban atmosphere. The obtained results indicate that the effective uptake coefficients of NO2 on urban grime in the presence of ultraviolet light [2.6 × 1015 photons cm–2 s–1 (300 nm < λ < 400 nm)] increased markedly from (1.1 ± 0.2) × 10–6 at 0% relative humidity (RH) to (5.8 ± 0.7) × 10–6 at 90% RH, exhibiting the following linear correlation with RH: γ­(NO2) = (7.4 ± 3.3) × 10–7 + (5.5 ± 0.6) × 10–8 × RH%. The flux densities of HONO mediated by light-induced heterogeneous conversion of NO2 (46 ppb) on urban grime were enhanced by ∼1 order of magnitude from (2.3 ± 0.2) × 109 molecules cm–2 s–1 at 0% RH to (1.5 ± 0.01) × 1010 molecules cm–2 s–1 at 90% RH. This study promotes light-induced NO2 chemistry on urban grime being an important source of HONO and suggests that further experiments be performed in the future.

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The photolysis of nitrous acid (HONO) is the main initiation source of hydroxyl radical (OH) which in turn is the main oxidant controlling the oxidation capacity of the indoor atmosphere.

As an emerging sustainable technology for harnessing solar energy, polymer solar cells (PSCs) have attracted extensive research attention due to their outstanding advantages, such as low cost, mechanical flexibility, and facile large-area fabrication. [1-7] Through the various strategies including molecular modulation on smallmolecular acceptors (SMAs), morphology optimization and interfacial engineering, the bulk-heterojunction devices based on polymer donors and SMAs have realized impressive power conversion efficiencies (PCEs) over 17%. [8-14] Among these achievements, Y6-series SMAs, which feature an A′-DAD-A′ structure, have demonstrated multiple cases of high-performance PSCs with optimized morphology and low energy loss. [15-17] Compared to SMA-based devices, all-PSCs provide additional merits such as high morphological stability, superior Fluorination of end groups has been a great success in developing efficient small molecule acceptors. However, this strategy has not been applied to the development of polymer acceptors. Here, a dihalogenated end group modified by fluorine and bromine atoms simultaneously, namely IC-FBr, is first developed, then employed to construct a new polymer acceptor (named PYF-T) for all-polymer solar cells (all-PSCs). In comparison with its non-fluorinated counterpart (PY-T), PYF-T exhibits stronger and red-shifted absorption spectra, stronger molecular packing and higher electron mobility. Meanwhile, the fluorination on the end groups down-shifts the energy levels of PYF-T, which matches better with the donor polymer PM6, leading to efficient charge transfer and small voltage loss. As a result, an all-PSC based on PM6:PYF-T yields a higher power conversion efficiency (PCE) of 14.1% than that of PM6:PY-T (11.1%), which is among the highest values for all-PSCs reported to date. This work demonstrates the effectiveness of fluorination of end-groups in designing high-performance polymer acceptors, which paves the way toward developing more efficient and stable all-PSCs.

Small molecular acceptors (SMAs) have gained extensive research attention as they offer many attractive features and enable highly efficient organic solar cells (OSCs) that cannot be achieved using fullerene acceptors....

A vertical wetted-wall flow-tube technique was used to explore the ionic strength effects at the air–water interface in mediating the sea-surface reaction between ozone (O3) and pyruvic acid (PA). The uptake coefficients of ozone on aqueous PA increase substantially with the concentrations of bromide (Br–) ions, clearly indicating that the dry deposition of ozone could be significantly enhanced due to the presence of carbonyl compounds such as PA at the bromide-rich sea surface. Based on the observed uptake coefficients, the estimated deposition velocity of ozone (100 ppb) for a nanomolar range of PA concentrations is ∼1 × 10–3 m s–1, which represents a significant contribution to the known deposition velocity of ozone at the sea surface. The analysis of reaction products by ultra-high-resolution Fourier transform-ion cyclotron resonance mass spectrometry suggests the formation of oligomers during both the dark and light-induced heterogeneous reactions between gaseous O3 and PA occurring at the surface of a dilute aqueous phase (representative of cloud droplets). The detected high-molecular-weight compounds are much more complex than the oligomeric species identified during the photolytic degradation of bulk aqueous PA alone.