Historical Trends of Atmospheric Black Carbon on Tibetan Plateau As Reconstructed from a 150-Year Lake Sediment Record

Black carbon (BC) is one of the key components causing global warming. Especially on the Tibetan Plateau (TP), reconstructing BC’s historical trend is essential for better understanding its anthropogenic impact. Here, we present results from high altitude lake sediments from the central TP. The results provide a unique history of BC over the past 150 years, from the preindustrial to the modern period. Although BC concentration levels in the Nam Co Lake sediments were lower than those from other high mountain lakes, the temporal trend of BC fluxes clearly showed a recent rise, reflecting increased emissions from anthropogenic activities. The BC records were relatively constant until 1900, then began to gradually increase, with a sharp rise beginning around 1960. Recent decades show about 2.5-fold increase of BC compared to the background level. The emission inventory in conjunction with air mass trajectories further demonstrates that BC in the Nam Co Lake region was most likely transported from South Asia. Rapid economic development in South Asia is expected to continue in the next decades; therefore, the influence of BC over the TP merits further investigations

Absorptive Behaviors and Photovoltaic Performance Enhancements of Alkoxy-Phenyl Modified Indacenodithieno[3,2‑<i>b</i>]thiophene-Based Nonfullerene Acceptors

Nonfullerene (NF) small molecular acceptors are very attractive for further improving the power conversion efficiencies (PCEs) of polymer solar cells (PSCs) to overcome the limited absorptive region and fixed-energy-level drawbacks of fullerene-based electronic acceptors (PC₆₁BM and PC₇₁BM). The acceptor–donor–acceptor (A-D-A)-type oligomers (<b>ITIC</b>) containing an electron-rich core (four hexyl-phenyl-substituted indacenodithieno­[3,2-<i>b</i>]­thiophene) as a donor motif sealed with 2-(3-oxo-2,3-dihydroinden-1-ylidene)-malononitrile as an acceptor motif has been intensively investigated, because of its excellent absorptive and photovoltaic properties. Side-chain modifications have been proven to be an effective approach to modulate the energy levels and absorptive behaviors of conjugated polymers, as well as conjugated small molecules. Through the introduction of various side-chain and end groups, a series of promisingly modified <b>ITIC</b>-based small molecules have been synthesized and well-studied. Herein, we reported three novel alkoxy-phenyl modified <b>ITIC</b>-type NF acceptors (namely, <b>pO-ITIC</b>, <b>mO-ITIC</b>, and <b>FpO-ITIC</b>), in which 4-hexyloxy-phenyl, 3-hexyloxy-phenyl, and 3-fluorine-4-hexyloxy-phenyl side-chains were connected on the indacenodithieno­[3,2-<i>b</i>]­thiophene core as the electron-donating segments of the A-D-A molecules. Both three small molecules exhibit good solubility in common solvents, finely tunable energy levels, and adjustable optical bandgaps. The 4-hexyloxy-phenyl and 3-hexyloxy-phenyl-substituted materials possess relatively low bandgaps (1.61 eV for <b>pO-ITIC</b> and 1.63 eV for <b>mO-ITIC</b>) and a 4.7% enhancement in the maximum extinction coefficient, compared to that of <b>ITIC</b>. As the result of the better absorption behaviors, inverted polymer solar cells based on <b>pO-ITIC</b> blended with <b>PTB7-Th</b> achieve an open-circuit voltage (<i>V</i>_oc) of 0.80 V, a short-circuit current (<i>J</i>_sc) of 14.79 mA/cm², and a fill factor (FF) of 59.1%, leading to a high-power conversion efficiency (PCE) of 7.51%, relative to the 7.31% PCE of <b>ITIC</b>-based device. By using a new thiazolothiazole-based wide-bandgap polymer (<b>PTZ-DO</b>, 1.98 eV) with deep HOMO energy level (−5.43 eV) to match the optical absorption and molecular energy levels with the three NF acceptors, excellent PCE values9.28% for <b>mO-ITIC</b> and 9.03% for <b>pO-ITIC</b>are obtained, which show increments of 15.3% and 12.2%, respectively, relative to that of <b>ITIC</b> (8.05%). This finding should offer useful guidelines for the design of novel NF acceptors for highly efficient PSCs through alkoxy-phenyl side-chains modified on the electron-donating moiety of A-D-A organic small molecules

Terpolymer Containing a <i>meta</i>-Octyloxy-phenyl-Modified Dithieno[3,2‑<i>f</i>:2′,3′‑<i>h</i>]quinoxaline Unit Enabling Efficient Organic Solar Cells

With the rapid development of small-molecule electron acceptors, polymer electron donors are becoming more important than ever in organic photovoltaics, and there is still room for the currently available high-performance polymer donors. To further develop polymer donors with finely tunable structures to achieve better photovoltaic performances, random ternary copolymerization is a useful technique. Herein, by incorporating a new electron-withdrawing segment 2,3-bis(3-octyloxyphenyl)dithieno[3,2-f:2′,3′-h]quinoxaline derivative (C12T-TQ) to PM6, a series of terpolymers were synthesized. It is worth noting that the introduction of the C12T-TQ unit can deepen the highest occupied molecular orbital energy levels of the resultant polymers. In addition, the polymer Z6 with a 10% C12T-TQ ratio possesses the highest film absorption coefficient (9.86 × 104 cm–1) among the four polymers. When blended with Y6, it exhibited superior miscibility and mutual crystallinity enhancement between Z6 and Y6, suppressed recombination, better exciton separation and charge collection characteristics, and faster hole transfer in the D–A interface. Consequently, the device of Z6:Y6 successfully achieved enhanced photovoltaic parameters and yielded an efficiency of 17.01%, higher than the 16.18% of the PM6:Y6 device, demonstrating the effectiveness of the meta-octyloxy-phenyl-modified dithieno[3,2-f:2′,3′-h]quinoxaline moiety to build promising terpolymer donors for high-performance organic solar cells

Humic-Like Substances (HULIS) in Aerosols of Central Tibetan Plateau (Nam Co, 4730 m asl): Abundance, Light Absorption Properties, and Sources

Humic-like substances (HULIS) are major components of light-absorbing brown carbon that play an important role in Earth’s radiative balance. However, their concentration, optical properties, and sources are least understood over Tibetan Plateau (TP). In this study, the analysis of total suspended particulate (TSP) samples from central of TP (i.e., Nam Co) reveal that atmospheric HULIS are more abundant in summer than that in winter without obvious diurnal variations. The light absorption ability of HULIS in winter is 2–3 times higher than that in summer. In winter, HULIS are mainly derived from biomass burning emissions in South Asia by long-range transport. In contrast, the oxidation of anthropogenic and biogenic precursors from northeast part of India and southeast of TP are major sources of HULIS in summer

Nonfullerene Polymer Solar Cells Based on a Main-Chain Twisted Low-Bandgap Acceptor with Power Conversion Efficiency of 13.2%

A new acceptor–donor–acceptor-structured nonfullerene acceptor, 2,2′-((2<i>Z</i>,2′<i>Z</i>)-(((4,4,9,9-tetrakis­(4-hexylphenyl)-4,9-dihydro-<i>s</i>-indaceno­[1,2-<i>b</i>:5,6-<i>b</i>′]­dithiophene-2,7-diyl)­bis­(4-((2-ethylhexyl)­oxy)­thiophene-4,3-diyl))­bis­(methanylylidene))­bis­(5,6-difluoro-3-oxo-2,3-dihydro-1<i>H</i>-indene-2,1-diylidene))­dimalononitrile (<b>i-IEICO-4F</b>), is designed and synthesized via main-chain substituting position modification of 2-(5,6-difluoro-3-oxo-2,3-dihydro-1<i>H</i>-indene-2,1-diylidene)­dimalononitrile. Unlike its planar analogue <b>IEICO-4F</b> with strong absorption in the near-infrared region, <b>i-IEICO-4F</b> exhibits a twisted main-chain configuration, resulting in 164 nm blue shifts and leading to complementary absorption with the wide-bandgap polymer (J52). A high solution molar extinction coefficient of 2.41 × 10⁵ M^–1 cm^–1, and sufficiently high energy of charge-transfer excitons of 1.15 eV in a J52:<b>i-IEICO-4F</b> blend were observed, in comparison with those of 2.26 × 10⁵ M^–1 cm^–1 and 1.08 eV for <b>IEICO-4F</b>. A power conversion efficiency of 13.18% with an open-circuit voltage (0.849 V), a short-circuit current density of 22.86 mA cm^–2, and a fill factor of 67.9% were recorded in J52:<b>i-IEICO-4F</b>-based polymer solar cells (PSCs), demonstrating that this main-chain twisted strategy can be a guideline that facilitates the development of new acceptors to maximize the efficiency in PSCs

Highly Efficient Solar Cells Based on the Copolymer of Benzodithiophene and Thienopyrroledione with Solvent Annealing

Highly efficient PBDTTPD-based photovoltaic devices with the configuration of ITO/poly­(3,4-ethylenedioxythiophene)-poly­(styrenesulfonate) (PEDOT:PSS)/PBDTTPD: methanofullerene (6,6)-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) (weight ratio being from 1:1 to 1:4)/LiF (5 Å)/Al (100 nm), were realized with ortho-dichlorobenzene (DCB) solvent annealing treatment. It was revealed that the best photovoltaic device was obtained when the blend ratio of PBDTTPD:PC₆₁BM was modulated to be 1:2 and processed with DCB solvent annealing for 12 h. The short-circuit current density (<i>J</i>_sc) and power conversion efficiency (PCE) values were measured to be 10.52 mA/cm² and 4.99% respectively, which were both higher than the counterparts treated with chlorobenzene (CB) solvent annealing or the thermal annealing. Atomic force microscopy measurements of the active layer after solvent annealing treatment were also carried out. The phase separation length scale of the PBDTTPD:PC₆₁BM­(1:2) layer was comparable to the exciton diffusion length when the active layer was treated under DCB solvent annealing, which facilitated effective exciton dissociation and carrier diffusion in the active layer. Therefore, highly efficient PBDTTPD-based photovoltaic devices could be achieved with DCB solvent annealing, which indicated that solvent annealing with proper solvent might be an easily processed, low-cost, and room-temperature alternative to thermal annealing for polymer solar cells