Incident allergic diseases in post-COVID-19 condition: multinational cohort studies from South Korea, Japan and the UK.

As mounting evidence suggests a higher incidence of adverse consequences, such as disruption of the immune system, among patients with a history of COVID-19, we aimed to investigate post-COVID-19 conditions on a comprehensive set of allergic diseases including asthma, allergic rhinitis, atopic dermatitis, and food allergy. We used nationwide claims-based cohorts in South Korea (K-CoV-N; n = 836,164; main cohort) and Japan (JMDC; n = 2,541,021; replication cohort A) and the UK Biobank cohort (UKB; n = 325,843; replication cohort B) after 1:5 propensity score matching. Among the 836,164 individuals in the main cohort (mean age, 50.25 years [SD, 13.86]; 372,914 [44.6%] women), 147,824 were infected with SARS-CoV-2 during the follow-up period (2020-2021). The risk of developing allergic diseases, beyond the first 30 days of diagnosis of COVID-19, significantly increased (HR, 1.20; 95% CI, 1.13-1.27), notably in asthma (HR, 2.25; 95% CI, 1.80-2.83) and allergic rhinitis (HR, 1.23; 95% CI, 1.15-1.32). This risk gradually decreased over time, but it persisted throughout the follow-up period (≥6 months). In addition, the risk increased with increasing severity of COVID-19. Notably, COVID-19 vaccination of at least two doses had a protective effect against subsequent allergic diseases (HR, 0.81; 95% CI, 0.68-0.96). Similar findings were reported in the replication cohorts A and B. Although the potential for misclassification of pre-existing allergic conditions as incident diseases remains a limitation, ethnic diversity for evidence of incident allergic diseases in post-COVID-19 condition has been validated by utilizing multinational and independent population-based cohorts.

National prevalence of smoking among adolescents at tobacco tax increase and COVID-19 pandemic in South Korea, 2005-2022.

Prior research has predominantly focused on the overall effects of the tobacco tax increase and the COVID-19 pandemic on adolescent smoking behavior. However, there is a need to examine both the immediate and sustained associations of these two factors on subgroups of adolescents, employing an interrupted time-series model. We aimed to investigate the immediate and sustained association of tobacco tax increase and the COVID-19 pandemic on adolescent smoking prevalence. This study utilized data from the Korea Youth Risk Behavior Web-Based Survey to analyze the prevalence of current smoking among all participants (CSP) and the prevalence of daily smoking among current smokers (DSP) of Korean adolescents (n = 1,159,995; mean, age 14.99; male 51.5%) over 18 years from 2005 to 2022. The study examined 18-year trends in CSP and DSP among Korean adolescents, emphasizing the influences of the 2015 tobacco tax increase and the COVID-19 pandemic, using ß coefficients and their differences (ßdiff) from an interrupted time-series ARIMA model. While CSP exhibited a decreasing trend, DSP exhibited an increasing trend. Tobacco tax increase was associated with both the short and long terms in smoking prevalence, however, the short-term association on prevalence (CSP, - 3.076 [95% CI, - 3.707 to - 2.445]; DSP, - 4.112 [95% CI, - 6.488 to - 1.735]) was stronger. The pandemic was associated with an immediate increase in DSP (9.345 [95% CI, 5.285-13.406]). These effects were strongest among adolescents from low economic status and those exposed to familial secondhand smoking. Supportive programs for adolescents in low-income families will help overcome the effects associated with the pandemic. As a tobacco tax increase was associated with a reduction in smoking prevalence, this could be one method to overcome the effects of the pandemic.

Chalcogen Atoms Regulate the Organic Solar Cell Performance of B-N-Based Polymer Donors.

Donor polymers play a key role in the development of organic solar cells (OSCs). B-N-based polymer donors, as new types of materials, have attracted a lot of attention due to their special characteristics, such as high E(T1), small ΔEST, and easy synthesis, and they can be processed with real green solvents. However, the relationship between the chemical structure and device performance has not been systematically studied. Herein, chalcogen atoms that regulate the OSCs performance of B-N-based polymer donors were systematically studied. Fortunately, the substitution of a halogen atom did not affect the high E(T1) and small ΔEST character of the B-N-based polymer. The absorption and energy levels of the polymer were systematically regulated by O, S, and Se atom substitution. The PBNT-TAZ:Y6-BO-based OSCs device demonstrated a high power conversion efficiency of 15.36%. Moreover, the layer-by-layer method was applied to further optimize the device performance, and the PBNT-TAZ/Y6-BO-based OSCs device yielded a PCE of 16.34%. Consequently, we have systematically demonstrated how chalcogen atoms modulated the electronic properties of B-N-based polymers. Detailed and systematic structure-performance relationships are important for the development of next-generation B-N-based materials.

Prenatal and postnatal exposure to antibiotics and risk of food allergy in the offspring: A nationwide birth cohort study in South Korea.

BACKGROUND: There are only preliminary studies examining the associations of postnatal antibiotic exposure with food allergy in childhood, and the effect of antibiotic exposure in utero has not been resolved. Thus, we aimed to investigate the effect of prenatal and postnatal antibiotic exposure on the risk of food allergy in childhood. METHODS: Using the nationwide birth cohort in South Korea, all 3,163,206 infants (pairing mother; n = 2,322,735) born in South Korea between 2010 and 2017 were included in the analysis. The primary outcome was the diagnosis of food allergy, and the observation period was between January 1, 2009, and December 31, 2020. We implemented four different designs for the study, which consisted of a full unmatched cohort, 1:1 propensity-matched cohort, sibling comparison cohort, and health screening cohort along with multiple subgroup analyses. RESULTS: During the follow-up period (median 6.92 years [IQR, 4.72-9.00]) of the 3,161,858 infants (52.6% male) in the birth cohort, 29,973 (1.9%) were diagnosed with food allergies. After a 1:1 propensity score matching, the use of antibiotics increased the risk of overall food allergy (prenatal [HR, 1.05; 95% CI, 1.04-1.09] and postnatal [HR, 1.05; 95% CI, 1.01-1.10] periods). The association was more significantly accentuated when antibiotic exposure was used in the short term, and the children were born preterm or with low birthweight; however, a trimester-specific effect was not observed. We observed more pronounced risks of food allergy in the health screening cohort (prenatal, 17%; postnatal, 15%), thus addressing the adverse effects of critical factors including maternal BMI, smoking status, and type of infant feeding. Similar trends were observed across all four differnt cohorts. CONCLUSION: This study reported a moderate association between early-life antibiotic use and subsequent food allergy during childhood throughout four different designs of analyses. This study suggests that clinicians need to consider the risks and benefits of antibiotics when administering antibiotics to individuals in the prenatal and postnatal periods.

High-Precision Tailored Polymer Molecular Weights for Specific Photovoltaic Applications through Ultrasound-Induced Simultaneous Physical and Chemical Events.

It is highly challenging to reproducibly prepare semiconducting polymers with targeted molecular weight tailored for next-generation photovoltaic applications. Once such an easily accessible methodology is established, which can not only contribute to overcome the current limitation of the statistically determined nature of semiconducting polymers, but also facilitate rapid incorporation into the broad synthetic chemists' toolbox. Here, we describe a simple yet robust ultrasonication-assisted Stille polymerization for accessing semiconducting polymers with high-precision tailored molecular weights (from low to ultrahigh molecular weight ranges) while mitigating their interbatch variations. We propose that ultrasound-induced simultaneous physical and chemical events enable precise control of the semiconducting polymers' molecular weights with high reproducibility to satisfy all the optical/electrical and morphological demands of diverse types of high-performance semiconducting polymer-based devices; as demonstrated in in-depth experimental screenings in applications of both organic and perovskite photovoltaics. We believe that this methodology provides a fast development of new and existing semiconducting polymers with the highest-level performances possible on various photovoltaic devices.

National Trends in the Prevalence of Screen Time and Its Association With Biopsychosocial Risk Factors Among Korean Adolescents, 2008-2021.

PURPOSE: Prior studies suggested an increase in screen time among adolescents during the COVID-19 pandemic; however, due to limited sample size and a short-term observation period, these associations are inconclusive and inconsistent. Thus, we aimed to compare screen time during the pandemic and the long-term trend through a Korean large-scale and long-term study of one million adolescents. METHODS: Data from 2008 to 2021 on 913,191 Korean adolescents aged 12-18 years were obtained via a nationwide, large-scale, and serial study. We investigated the change of screen time use over time and the change in trend before and during the pandemic (2008-2019 vs. 2020-2021) by using weighted linear regression model with estimates of ß-coefficients and 95% confidence intervals (CIs). Moreover, we analyzed the differences in vulnerability of biopsychosocial factor before and during the pandemic. RESULTS: A total of 913,191 adolescents were included in this analysis. During the pandemic, the overall screen time of Korean adolescents significantly increased compared to the expected based on the prepandemic period during the pre-COVID-19 period (weighted screen time before the pandemic [133.24 min/day; 95% CI, 132.08-134.40] vs. during the pandemic [303.66 min/day; 95% CI, 300.59-306.73]; ßdiff 0.331; 95% CI, 0.311-0.351). Comparing before and during the pandemic, potential risk factors associated with screen exposure included female sex, sadness, suicidal thoughts, alcohol consumption, low educational level of parents, low level of vigorous physical activity, middle school students, and low household income. DISCUSSION: Through large-scale nationwide study, this study described the 14-year trend of screen time among Korean adolescents. In the era of COVID-19, the prevalence of screen exposure has been increasing more rapidly than before at the population level. Also, the pandemic amplified the differences in screen time across grade, sex, sadness, suicidal thoughts, smoking, alcohol consumption, education level of parents, physical activity, and household income groups.

Hand and Oral Hygiene Practices of South Korean Adolescents Before and During the COVID-19 Pandemic.

Importance: Only a few studies have examined the long-term trends of hand and oral hygiene, especially among adolescents. Objective: To investigate the 15-year trends in frequency of handwashing and toothbrushing and examine the factors associated with hand and oral hygiene, particularly during the COVID-19 pandemic. Design, Setting, and Participants: This cross-sectional study, performed from January 1, 2008, to December 31, 2022, used general population-based data from 963 644 individuals in a national representative survey (Korea Youth Risk Behavior Web-based Survey [KYRBS]). Exposure: COVID-19 pandemic. Main Outcomes and Measures: Trends in hand and oral hygiene practices were measured by how frequently adolescents washed their hands and whether they fulfilled the recommended guidelines for toothbrushing. An interrupted time series analysis using linear and logistic regression models was performed to assess any associations with the COVID-19 pandemic. Hand and oral hygiene behaviors before and during the pandemic in each sociodemographic subgroup were also compared. Results: In the 963 644 adolescents (495 697 [51.4%] male; mean [range] age, 15.01 [12-18] years) who participated in the KYRBS from 2008 to 2022, a 73.3% (95% CI, 59.4%-97.4%; P < .001) immediate increase was seen in overall hand hygiene behavior at the onset of the COVID-19 pandemic compared with the prepandemic period, with a sustained decrease thereafter (ß = -0.018; 95% CI, -0.022 to -0.015; P < .001). Meanwhile, no immediate increase was observed in terms of overall oral hygiene behavior (0.1%; 95% CI, -0.9% to 1.1%; P = .82); however, there was a sustained decrease during the pandemic (ß = -0.018; 95% CI, -0.020 to -0.016; P < .001). Older age, female sex, nonsmoking status, alcohol use, low household economic level, and poor school performance were significantly associated with poor hand hygiene during the pandemic. Conclusions and Relevance: In this cross-sectional study of South Korean adolescents, an increase in the prevalence of hand hygiene was observed during the early pandemic; however, this prevalence decreased over time. Meanwhile, the decrease in the prevalence of oral hygiene was more pronounced during the pandemic. This study recommends stronger guidelines for adolescent health coaches, such as teachers or public health advisers, regarding hygiene behaviors, even after the COVID-19 pandemic ends.

National and regional trends in the prevalence of type 2 diabetes and associated risk factors among Korean adults, 2009-2021.

Disproportionate impact of COVID-19 on socioeconomic and behavioral variables may have impacted the prevalence of diabetes. We utilized nationwide long-term serial study from the 2009 to 2021 Korea Community Health Survey (KCHS). We explored national and regional prevalence and trends of diabetes according to the socioeconomic and behavioral factors before and during the pandemic. Also, we interpreted which groups became more vulnerable to the prevalence of diagnosed diabetes during the pandemic. A total of 2,971,349 adults aged (19 to 39, 40 to 59, and ≥ 60 years) were included in the analysis. The prevalence of diagnosed diabetes increased slowly during the pandemic (11.6% [95% CI 11.5-11.7] in 2020 and 12.4% [95% CI 12.3-12.6] in 2021), compared to the pre-pandemic era (7.9% [95% CI 7.8-7.9] in 2009-2011 and 11.3% [95% CI 11.3-11.4] in 2018-2019). Also, women, low-income group, low-educational group, and infrequent walking group showed less prevalence of diagnosed diabetes than the others. The diabetic population increased slowly than expected during the pandemic. The pandemic seems to contribute to an unanticipated increase in under-diagnosis of diabetes among the already minority. This study may suggest reinforcing access to healthcare services among the minority during the pandemic.

Conformational Locking Control of 2D Outer Side Chains via Fluorine Atom Positioning for Improving the Thermal Stability of Organic Solar Cells.

Alongside high power conversion efficiencies (PCEs), device stability, especially thermal issues, is another key factor for the successful commercialization of nonfullerene acceptor (NFA)-based organic solar cells (OSCs). Considering the significant effects of the side-chain engineering of NFAs on molecular packing and/or locking strongly associated with the thermal stability of OSCs, herein, we present two new isomeric NFAs with 4-fluoro- and 2-fluoro-substituted hexylphenyl two-dimensional (2D) outer side chains (4FY and 2FY, respectively). In contrast with the 2FY having a horizontal stretching conformation, 4FY exhibits a diagonal stretching conformation of the 2D outer side chains and a higher dipole moment, resulting in a huge difference in their crystalline/aggregation characteristics, i.e., 4FY possesses a higher crystallinity with a denser molecular packing than the 2FY neat film, as evidenced by thermal and morphological characterizations. Encouragingly, relative to the one based on 2FY, the OSC based on 4FY delivers a PCE as high as 16.4%, together with excellent thermal stability (88.4% PCE retention under 85 °C for 360 h), which is attributed to a more optimal and robust blend morphology induced by its better compatibility into the used donor component and stronger crystallinity. This work demonstrates that in addition to the improved photovoltaic property, the appropriate F-positioning on the 2D outer side chains can play a key role in controlling their conformations, which can promote the increase of the thermal stability of OSCs.

High-Performance Electrochemical and Photoelectrochemical Water Splitting at Neutral pH by Ir Nanocluster-Anchored CoFe-Layered Double Hydroxide Nanosheets.

Highly efficient electrocatalysts for the oxygen evolution reaction (OER) in neutral electrolytes are indispensable for practical electrochemical and photoelectrochemical water splitting technologies. However, there is a lack of good, neutral OER electrocatalysts because of the poor stability when H+ accumulates during the OER and slow OER kinetics at neutral pH. Herein, we report Ir species nanocluster-anchored, Co/Fe-layered double hydroxide (LDH) nanostructures in which the crystalline nature of LDH-restrained corrosion associated with H+ and the Ir species dramatically enhanced the OEC kinetics at neutral pH. The optimized OER electrocatalyst demonstrated a low overpotential of 323 mV (at 10 mA cm-2) and a record low Tafel slope of 42.8 mV dec-1. When it was integrated with an organic semiconductor-based photoanode, we obtained a photocurrent density of 15.2 mA cm-2 at 1.23 V versus reversible hydrogen in neutral electrolyte, which is the highest among all reported photoanodes to our knowledge.

Combining dithieno[3,2-f:2',3'-h]quinoxaline-based terpolymer and ternary strategies enabling high-efficiency organic solar cells.

By incorporating a dithieno[3,2-f:2',3'-h]quinoxaline unit into a PM6 polymer backbone, we developed a novel terpolymer family, demonstrating composition-dependent optical, electrochemical, and morphological characteristics. Organic solar cells based on the combination of a terpolymer and ternary strategy achieved a high power conversion efficiency of 17.60%, demonstrating the validity of our combination strategy.

Vinylene-Inserted Asymmetric Polymer Acceptor with Absorption Approaching 1000 nm for Versatile Applications in All-Polymer Solar Cells and Photomultiplication-Type Polymeric Photodetectors.

The emerging polymerized small-molecule acceptors (PSMAs) with near-infrared (NIR) absorption have not only significantly boosted the power conversion efficiencies (PCEs) of all-polymer solar cells (all-PSCs) but have also exhibited great potential for sensitive NIR polymeric photodetectors (PPDs). However, there is no report regarding PSMAs with photo-response that can approach 1000 nm, which is an important criterion for applications in NIR-responsive all-PSCs and PPDs. Herein, by unidirectionally inserting vinylene segments into a selenophene-rich polymer backbone to improve the electron-donating strength and quinoidal character, an asymmetric PSMA, namely, PY3Se-1V, was developed, which showed an extensively red-shifted absorption approaching 1000 nm. The PBDB-T:PY3Se-1V-based binary all-PSCs achieve a decent PCE of 13.2% and a record-high photocurrent density of 25.9 mA cm-2 due to the significantly broadened photo-response and efficient photon-to-electron conversion. More encouragingly, narrowband photomultiplication (PM)-type PPDs based on poly(3-hexylthiophene-2,5-diyl) (P3HT):PY3Se-1V were developed, delivering an exceptionally high external quantum efficiency of 3680% and a responsivity of 28 A W-1 at an NIR peak of 960 nm under -50 V bias, which is reported for the first time in PM-type PPDs with a response approaching 1000 nm.

Synthesis of Thermoplastic Polyurethanes Containing Bio-Based Polyester Polyol and Their Fiber Property.

Among the starting materials of thermoplastic polyurethanes (TPUs), it was confirmed that succinic acid-based polyester biopolyols having different molecular weights (Mn = 1000, 2000, and 4000) affect the physicochemical properties of the final polymer significantly. Bio-TPUs synthesized through a solvent-free one-shot polymerization process were synthesized with a polyester polyol, 1,4 butanediol (BDO), and 4,4'-methylene diphenyl diisocyanate (MDI) in a molar ratio of 1:1:2. As a control group, one typical petroleum-based TPU was synthesized and characterized along with other bio-based TPUs. Representative petroleum-based and bio-based TPUs synthesized were manufactured as monofilaments with a diameter of about 0.2 mm through an extrusion process with different draw ratios (4, 5, and 6 times). The molecular weight and structural properties of the TPUs were characterized by GPC and FT-IR analysis and thermal characterization by DSC and TGA analysis. Petroleum-based TPU and bio-based TPU having the same molecular weight soft segment (SS) tended to have similar molecular weight and hard segment (HS) content. TPUs with high HS content had excellent thermal stability, enabling stable extrusion of TPUs. In addition, it was confirmed that the bio-based TPU fibers produced in this way had a tensile strength corresponding to the physical properties of petroleum-based TPU fibers and an excellent elastic recovery rate of almost 100 %. These results indicate the application potential of bio-TPU.

Are All Urban Parks Robust to the COVID-19 Pandemic? Focusing on Type, Functionality, and Accessibility.

Many people visited urban parks during the COVID-19 pandemic to reduce the negative effects of lack of physical activity, social isolation, anxiety, and depression. It is unclear whether all parks are robust against the pandemic, helping people sustain healthy daily living through the diverse activities within them. Nevertheless, few studies have identified the specific relationship between park visits and the COVID-19 pandemic. Therefore, this study aims to demonstrate how physical features such as type, functionality, and access influenced daily visiting to parks during the pandemic, using mobile phone data at a micro level. This study first classified urban parks as point-type parks with an area of less than 1 ha, plane-type parks with 1 ha or more, and line-type parks with elongated shapes, while measuring accessibility to residential, employment, transportation, and auxiliary facilities within the park. The study employed the multi-level regression model with random intercept to investigate the effects of differing park visits, focusing on Goyang city, South Korea. Our analysis results identified that easy access from home was more important than the park size during the pandemic. If we look at the types of parks, the use of both plane- and point-type parks increased more than that of line-type parks. However, line-type parks near homes, along with shopping and sports facilities, were found to be more robust to the pandemic. These findings can be informative to provide specific guidelines to fulfill the enhanced role of parks in sustaining public health during an infectious disease pandemic that may strike again.

Rational Regulation of the Molecular Aggregation Enables A Facile Blade-Coating Process of Large-area All-Polymer Solar Cells with Record Efficiency.

Developing robust materials is very critical and faces a big challenge for high-performance large-area all-polymer solar cells (all-PSCs) by printing methods. Herein, the authors combine the advantages of the terpolymerization strategy with the non-conjugated backbone strategy to regulate the molecular aggregation rationally during the film-forming printing process, facilitating a facile printing process for large-area all-PSCs. A series of terpolymer acceptors PYSe-Clx (x = 0, 10, 20, and 30) is also developed, which can effectively fine-tune the morphology and photoelectric properties of the active layer. The PBDB-T: PYSe-Cl20-based all-PSC delivers a significantly improved power cconversion efficiency (PCE) than the one with PBDB-T: PYSe (14.21% vs 12.45%). By addition of a small amount of non-conjugated polymer acceptor PTClo-Y, the ternary all-PSC reaches a PCE of 15.26%. More importantly, the regulation of molecular aggregation enables a facile blade-coating process of the large-area device. A record PCE of 13.81% for large-area devices (1.21 cm2 ) is obtained, which is the highest value for large-area all-PSCs fabricated by blade-coating. The environmentally friendly solvent processed large-area device also obtains an excellent performance of 13.21%. This work provides a simple and effective molecular design strategy of robust materials for high-performance large-area all-PSCs by a printing process.

Volatile Solid Additive-Assisted Sequential Deposition Enables 18.42% Efficiency in Organic Solar Cells.

Morphology optimization of active layer plays a critical role in improving the performance of organic solar cells (OSCs). In this work, a volatile solid additive-assisted sequential deposition (SD) strategy is reported to regulate the molecular order and phase separation in solid state. The OSC adopts polymer donor D18-Cl and acceptor N3 as active layer, as well as 1,4-diiodobenzene (DIB) as volatile additive. Compared to the D18-Cl:N3 (one-time deposition of mixture) and D18-Cl/N3 (SD) platforms, the D18-Cl/N3(DIB) device based on DIB-assisted SD method exhibits a finer phase separation with greatly enhanced molecular crystallinity. The optimal morphology delivers superior charge transport and extraction, offering a champion power conversion efficiency of 18.42% with significantly enhanced short-circuit current density (Jsc ) of 27.18 mA cm-2 and fill factor of 78.8%. This is one of the best performances in binary SD OSCs to date. Angle-dependent grazing-incidence wide-angle X-ray scattering technique effectively reveals the vertical phase separation and molecular crystallinity of the active layer. This work demonstrates the combination of volatile solid additive and sequential deposition is an effective method to develop high-performance OSCs.

Regiospecific N-alkyl substitution tunes the molecular packing of high-performance non-fullerene acceptors.

The rapid development of non-fullerene acceptors (NFAs) with strong near-infrared absorption has led to remarkably enhanced short-circuit current density (Jsc) values in organic solar cells (OSCs). NFAs based on the benzotriazole (Bz) fused-ring π-core have great potential in delivering both high Jsc and decent open-circuit voltage values due to their strong intramolecular charge transfer with reasonably low energy loss. In this work, we have designed and synthesized a series of Bz-based NFAs, PN6SBO-4F, AN6SBO-4F and EHN6SEH-4F, via regiospecific N-alkyl engineering based on the high-performance NFA mBzS-4F that was reported previously. The molecular packing of mBzS-4F, AN6SBO-4F, and EHN6SEH-4F single crystals was analyzed using X-ray crystallography in order to provide a comprehensive understanding of the correlation between the molecular structure, the charge-transporting properties, and the solar cell performance. Compared with the typical honeycomb single-crystal structure of Y6 derivatives, these NFAs exhibit distinctly different molecular packing patterns. The strong interactions of terminal indanone groups in mBzS-4F and the J-aggregate-like packing in EHN6SEH-4F lead to the formation of ordered 3D networks in single-crystals with channels for efficient charge transport. Consequently, OSCs based on mBzS-4F and EHN6SEH-4F show efficient photon-to-current conversions, achieving the highest power conversion efficiency of 17.48% with a Jsc of 28.83 mA cm-2.

Effects of the Polarity and Bulkiness of End-Functionalized Side Chains on the Charge Transport of Dicyanovinyl-End-Capped Diketopyrrolopyrrole-Based n-Type Small Molecules.

When designing organic semiconductors, side-chain engineering is as important as modifying the conjugated backbone, which has a significant impact on molecular ordering, morphology, and thus electronic device performance. We have developed three dicyanovinyl-end-capped donor-acceptor diketopyrrolopyrrole-based n-type small molecules (C2C9CN, SiC4CN, and EH4PCN) bearing an identical length of alkyl spacer yet different end-functionalized side chains (i.e., alkyl-, siloxane-, and phosphonate-end pendants). The effects of the end-functionalized side chains on the intrinsic molecular properties, microstructure, and charge transport of the small-molecule series were investigated. In comparison with the alkyl-end side chains, incorporating siloxane-end side chains into the backbone facilitates 2D edge-on oriented high intergrain connectivity/crystallinity and compatibility with the substrate surface, whereas the phosphonate-end analogues have an adverse effect on the film-forming quality due to high polarity. Thereby, an organic field-effect transistor fabricated by SiC4CN shows the best electron mobility up to 1.59 × 10-1 cm2 V-1 s-1 along with a high current on/off ratio >105. This study contributes to our understanding of the role of the end-functionalized side chains (e.g., the effects of polarity and bulkiness of the end groups) for the development of high-performance semiconductors.

N-Type Quinoidal Polymers Based on Dipyrrolopyrazinedione for Application in All-Polymer Solar Cells.

Conjugated molecules and polymers with intrinsic quinoidal structure are promising n-type organic semiconductors, which have been reported for application in field-effect transistors and thermoelectric devices. In principle, the molecular and electronic characteristics of quinoidal polymers can also enable their application in organic solar cells. Herein, two quinoidal polymers, named PzDP-T and PzDP-ffT, based on dipyrrolopyrazinedione were synthesized and used as electron acceptors in all-polymer solar cells (all-PSCs). Both PzDP-T and PzDP-ffT showed suitable energy levels and wide light absorption range that extended to the near-infrared region. When combined with the polymer donor PBDB-T, the resulting all-PSCs based on PzDP-T and PzDP-ffT exhibited a power conversion efficiency (PCE) of 1.33 and 2.37 %, respectively. This is the first report on the application of intrinsic quinoidal conjugated polymers in all-PSCs. The photovoltaic performance of the all-PSCs was revealed to be mainly limited by the relatively poor and imbalanced charge transport, considerable charge recombination. Detailed investigations on the structure-performance relationship suggested that synergistic optimization of light absorption, energy levels, and charge transport properties is needed to achieve more successful application of intrinsic quinoidal conjugated polymers in all-PSCs.

Novel High-Efficiency Polymer Acceptors via Random Ternary Copolymerization Engineering Enables All-Polymer Solar Cells with Excellent Performance and Stability.

Continuous breakthroughs have been achieved in improving the efficiency of all-polymer solar cells (all-PSCs) using diimide-based polymer acceptors, and their easy-to-synthesize, low-cost, and high stability attributes make them potential candidates for use in commercial all-PSCs. However, their low light absorption coefficient, strong aggregation, and poor adaptability with high-efficient polymer donors still limit further improvements in the device performance. Here, we combine the advantages of fluorinated bithiophene and rhodanine dye molecules to create low-cost diimide-based polymer acceptors, PNDI-2FT-TR10 and PNDI-2FT-TR20, by random copolymerization for achieving highly efficient and stable all-PSCs. The synergistic effects of fluorine atoms and rhodanine dye molecules not only significantly improve the absorption coefficient but also enable enhanced miscibility and stability of the blend film. When blended with a PM6 donor, the PNDI-2FT-TR10-based device exhibits a notable power conversion efficiency (PCE) of 10.71% with a short-circuit current (JSC) of 17.32 mA cm-2. Note that both the PCE and JSC show outstanding values for diimide-based all-PSCs, and this is the first report on blending diimide-based polymer acceptors with the PM6 donor to achieve high-performance all-PSCs. Moreover, the favorable morphology of the active layer enables the device to have good thickness tolerance and thermal stability. The results demonstrate that the absorption coefficients, blend morphology, and photovoltaic properties of all-PSCs could be rationally optimized by a random copolymer.