Design and evaluation of a simulated wound management course for postgraduate year one surgery residents

Background

It is vital to cover wound management knowledge and operations in the early stages of resident training. With this in mind, a simulated wound management course for postgraduate year one surgery residents (PGY1s) was designed and its effectiveness was evaluated.

Methods

A retrospective quasi-experimental method was used. PGY1s in 2014 constituted the control group, and PGY1s in 2015 and 2016 constituted the intervention group. The course given to the control group comprised didactic teaching followed by deliberate practice plus immediate personalized feedback. The newly designed course given to the intervention group was reconstructed and disassembled into four components according to the simulation-based mastery learning model, which were baseline test, interactive learning, basic skills practice, and reflective learning. The same performance assessments were used in the control and intervention group, including process measurement and outcome measurement.

Results

The process measurement showed that the intervention group’s scores were significantly higher in the “dissociation of subcutaneous tissue” and “quality of suturing and knots”. The outcome measurement showed that the accuracy of debridement was greatly improved and both key and total suture numbers were significantly higher in the intervention group.

Conclusions

Simulation-based mastery learning was incorporated into our proposed course framework, promoting the learning outcome of PGY1s. It has the potential to be adapted for other surgical training sites for residents in China.

Medical students' motivation and academic performance: the mediating roles of self-efficacy and learning engagement

Background: Motivation matters in medical students' academic performance. However, few studies have specifically examined how motivation and external environmental factors (e.g., institutions) affect medical students' performance with large-scale data sets. The roles of self-efficacy and learning engagement in the mechanisms that govern how motivation affects academic performance are still unclear.Objective: This study aims to advance a comprehensive understanding about the relationships between medical students' motivation, self-efficacy, learning engagement, and academic performance in a nationwide survey, taking students' demographic factors and sociocultural environments into consideration.Design: We collected data from 1930 medical students in China. We probed the relations between studying variables. We then performed structural equation model (SEM) analysis to examine the mediating roles of self-efficacy and learning engagement on the relationship between motivation and academic performance. We further carried out multiple-group SEM analyses to compare differences between males and females, and between students in key universities and colleges (KUCs) and non-key universities and colleges (NKUCs).Results: Medical students in KUCs demonstrated significantly higher intrinsic motivation, better academic performance and lower extrinsic motivation than those in NKUCs. Male students reported higher intrinsic motivation but surprisingly lower academic performance than females. The total effect of intrinsic motivation on academic performance was larger than that of extrinsic motivation. There were significant indirect effects of either intrinsic or extrinsic motivation on academic performance through learning engagement. Besides, both intrinsic motivation and extrinsic motivation predicted self-efficacy; however, the direct effect of self-efficacy on academic performance was not significant.Conclusions: This study provided researchers with a holistic picture of students' types of motivation in relation to academic performance. Findings from this study can help in rethinking the role of self-efficacy in medicine, in finding more effective interventions for promoting medical students' levels of motivation, and in developing motivation-related counselling methods for different groups of medical students.

Effects of Paper Mulberry (Broussonetia papyrifera) Leaf Extract on Growth Performance and Fecal Microflora of Weaned Piglets

The paper mulberry (Broussonetia papyrifera) leaf is rich in alkaloids and flavonoids, which has high medicinal and feeding value. We aimed to analyze the effects of B. papyrifera leaf extract on growth performance, antioxidant capacity, immune functions, and fecal microflora of weaned piglets. Thirty healthy, 28-day-old piglets were randomly assigned to three groups and fed with a basal diet supplemented with 0, 150, and 300 g/t B. papyrifera leaf extract for 42 days (control group, group I, and group II) separately. The result revealed that the final weight of piglets in group II was higher than the other groups, and the diarrhea rate in this group was 62.9% lower than in the control group. The feed conversion ratio in group I was significantly lower than the other two groups. Higher blood urine nitrogen concentration was noted in group II, higher glutathione peroxidase and catalase in group II, higher superoxide dismutase in the control group, and higher immune globulins (Ig) IgG, IgA, and IgM in group II. There was no significant difference in community richness and community diversity among the three groups of fecal samples. The relative level of Roseburia was higher in groups I and II, while Lactobacillus was higher in the control group. In conclusion, supplementation with B. papyrifera leaf extract at a certain dosage can increase growth performance and antioxidant capacity of weaned piglets, reduce the occurrence of diarrhea, enhance immune functions and disease resistance, and affect the composition of fecal microflora.

Association between medical students' prior experiences and perceptions of formal online education developed in response to COVID-19: a cross-sectional study in China

OBJECTIVES

(1) Understanding the characteristics of online learning experiences of Chinese undergraduate medical students; (2) Investigating students' perceptions of ongoing online education developed in response to COVID-19 and (3) Exploring how prior online learning experiences are associated with students' perceptions.

DESIGN

Students' familiarity with online learning modes and corresponding perceived usefulness (PU) according to their previous experiences were investigated using an online survey. The survey also collected data on students' perceptions through their evaluation of and satisfaction with current online learning.

SETTING

In response to the educational challenges created by COVID-19, medical schools in China have adopted formal online courses for students.

PARTICIPANTS

The questionnaire was sent to 225 329 students, of whom 52.38% (118 080/225 329) replied, with valid data available for 44.18% (99 559/225 329).

METHODS

Pearson correlations and t-tests were used to examine the relationship between familiarity and PU. Multiple linear regression and logistic regression analyses were used to determine the impact of prior learning experiences and its interactions with gender, area, learning phase and academic performance on students' perceptions.

RESULTS

Students' PU had a significant positive correlation with their familiarity with online learning modes (p<0.01). Students' evaluation of and satisfaction with their current online education were positively associated with their familiarity (β=0.46, 95% CI 0.45 to 0.48, p<0.01; OR 1.14, 95% CI 1.13 to 1.14, p<0.01) with and PU (β=3.11, 95% CI 2.92 to 3.30, p<0.01; OR 2.55, 95% CI 2.37 to 2.75, p<0.01) of online learning. Moreover, the higher the students' learning phases, the lower the associations between PU and students' evaluation of and satisfaction with ongoing online education.

CONCLUSIONS

Medical students in China have experiences with various online learning modes. Prior learning experiences are positively associated with students' evaluation of and satisfaction with current online education. Higher learning phases, in which clinical practices are crucial, and high academic performance led to lower evaluation and satisfaction scores.

Boron(iii) β-diketonate-based small molecules for functional non-fullerene polymer solar cells and organic resistive memory devices

A class of acceptor-donor-acceptor chromophoric small-molecule non-fullerene acceptors, 1-4, with difluoroboron(iii) β-diketonate (BF2bdk) as the electron-accepting moiety has been developed. Through the variation of the central donor unit and the modification on the peripheral substituents of the terminal BF2bdk acceptor unit, their photophysical and electrochemical properties have been systematically studied. Taking advantage of their low-lying lowest unoccupied molecular orbital energy levels (from -3.65 to -3.72 eV) and relatively high electron mobility (7.49 × 10-4 cm2 V-1 s-1), these BF2bdk-based compounds have been employed as non-fullerene acceptors in organic solar cells with maximum power conversion efficiencies of up to 4.31%. Moreover, bistable resistive memory characteristics with charge-trapping mechanisms have been demonstrated in these BF2bdk-based compounds. This work not only demonstrates for the first time the use of a boron(iii) β-diketonate unit in constructing non-fullerene acceptors, but also provides more insights into designing organic materials with multi-functional properties.

Effects of the penalty mechanism against traffic violations in China: A joint frailty model of recurrent violations and a terminal accident

A penalty mechanism is usually considered as a powerful means to reduce the probability of traffic violations and accidents by encouraging drivers to comply with traffic regulations. Penalty point and fine strategies are often used in parallel. Different degrees of penalty points and/or fines are imposed according to the specific violation behavior of drivers. However, the question of whether each penalty produces positive effects in maintaining a driver's compliance with traffic regulations and promoting the driver's traffic safety is still unanswered. This study focuses on quantifying the effects of penalty point and fine strategies on violation recurrences and accident occurrences of drivers. A frailty survival analysis method is conducted to jointly model the occurrence of violation and accident events of each individual. The frailty term in the model is leveraged to address the unobserved heterogeneity among drivers. Personal characteristics and penalty status are also incorporated as covariates in the model. Actual violation and accident data from a province in China are utilized to calibrate the model. The results show that penalty point strategy exhibits deterrent and binding effects; however, penalty fine strategy does not show the expected effects. The number of years of driving is also a significant factor that influences violation recurrence and accident occurrence. The present study provides insightful information for improving violation penalty mechanisms.

Medical career expectations of academically talented high school students: a nationwide cross-sectional study in China

BACKGROUND

Academically talented high school students (ATHSSs), an exceptional cohort, are not well studied for their career expectations, especially for those with medical career expectation (MCE). Nowadays, the public perception of the medical profession is changing in China. The purpose of this study was to answer questions about 'is medicine attractive for ATHSSs and 'what factors affect medical career expectations (MCE) for ATHSSs' in China.

METHODS

A total of 16,479 representative ATHSSs in senior three completed a questionnaire and four different academic tests. Frequency statistics showed the proportion of ATHSSs with MCE. Unpaired t-tests were performed to find out the differences in demographics, family background, and academic performance between students with and without MCE. The logit models analysis were applied to explore the potential factors that affected the MCE of this exceptional group of students.

RESULTS

ATHSSs with MCE accounted for 20.6% (ranking 7/18) of the respondents. They were more likely to be female, came from relatively poorer families, lived in a rural area, and performed significantly worse in all academic tests except for mathematics, compared with those without MCE. In addition, the results revealed that gender (β = - 0.436, p < 0.01), region of hometown (β = - 103, p < 0.1), mother's years of schooling (β = - 0.019, p < 0.05), and father's occupational status (β = - 0.005, p < 0.01) contributed significantly to the MCE of academically talented students. Better performance in mathematics affected the MCE of ATHSSs taking the liberal arts and science tests differently.

CONCLUSIONS

We found the medical career is becoming unattractive to academically talented students and the medical career may be losing their aura in China. Students who have medical career expectations are likely to be females and to have a weak family background.

Long non-coding RNA MEG3 is involved in osteogenic differentiation and bone diseases (Review)

Osteogenic differentiation originating from mesenchymal stem cells (MSCs) requires tight co-ordination of transcriptional factors, signaling pathways and biomechanical cues. Dysregulation of such reciprocal networks may influence the proliferation and apoptosis of MSCs and osteoblasts, thereby impairing bone metabolism and homeostasis. An increasing number of studies have shown that long non-coding (lnc)RNAs are involved in osteogenic differentiation and thus serve an important role in the initiation, development, and progression of bone diseases such as tumors, osteoarthritis and osteoporosis. It has been reported that the lncRNA, maternally expressed gene 3 (MEG3), regulates osteogenic differentiation of multiple MSCs and also acts as a critical mediator in the development of bone formation and associated diseases. In the present review, the proposed mechanisms underlying the roles of MEG3 in osteogenic differentiation and its potential effects on bone diseases are discussed. These discussions may help elucidate the roles of MEG3 in osteogenic differentiation and highlight potential biomarkers and therapeutic targets for the treatment of bone diseases.

High-Sensitivity Visible-Near Infrared Organic Photodetectors Based on Non-Fullerene Acceptors

Highly sensitive solution-processed organic photodetectors (OPDs) with a broadband response ranging from visible to near infrared (NIR) and excellent overall device performance are demonstrated. The OPDs were fabricated from a blend consisting of a wide-band gap polymer donor and a newly developed fused octacylic small-molecule electron acceptor with an acceptor-donor-acceptor structure, which shows relatively high and balanced hole/electron mobility and allows for a thicker photo-active layer (∼300 nm). In conjunction with the use of an optimized inverted device structure, the dark current density of the OPDs was suppressed to an ultralow level of (8.3 ± 5.5) × 10^-10A cm^-2 at a bias of -1 V and the capability to direct weak light intensity is down to 0.24 pW cm^-2; both are among the lowest reported values for OPDs. Owing to the low shot noise enabled by the inverted structure and the low thermal noise due to the high shunt resistance of the device, the obtained OPDs show a spectrally flat photoresponse in the range of 350-950 nm (UV-vis-NIR) and a maximal specific detectivity (D*) of (2.1 ± 0.1) × 10¹³ Jones at 800-900 nm, which are among the best results of NIR OPDs reported to date and represents a highly sensitive photodetector for weak optical signal detection. Besides, the OPDs show a wide bandwidth of 30 kHz, a fast temporal response time around 12 us ∼14 us, and a large linear dynamic range of 106 dB.

Copper sulfate-induced endoplasmic reticulum stress promotes hepatic apoptosis by activating CHOP, JNK and caspase-12 signaling pathways

Copper (Cu), a transition metal, is an essential trace element in human and animal nutrition at low concentration, but Cu has toxic effects on tissues and organs at high concentration. Endoplasmic reticulum (ER) is a toxicological target in Cu poison. Thus far, no studies have focused on the relationship among copper, endoplasmic reticulum (ER) stress and apoptosis in animal and human livers. In the present study, mice treated with copper sulfate (CuSO₄) were used to assess the impacts of copper on ER stress and hepatic apoptosis. A total of 240 mice were orally administered with 0 (control), 10, 20 and 40 mg/kg of CuSO₄ for 42 days. The results indicated that CuSO₄ at 10 mg/kg markedly induced hepatocyte apoptosis and ER stress. In addition, ER stress was characterized by the increased mRNA and protein levels of glucose-regulated protein 78 (GRP78) and 94 (GRP94). Furthermore, ER stress-triggered 3 apoptotic pathways were also activated by the increased intracellular calcium and up-regulated expression levels of genes involved in growth arrest- and DNA damage-inducible gene 153 (Gadd153/CHOP), c-Jun N-terminal kinase (JNK) and cysteine aspartate-specific protease 12 (caspase-12) signaling pathways in CuSO₄-treated mice. In conclusion, CuSO₄-induced ER stress can promote hepatic apoptosis in mice by activating CHOP, JNK and caspase-12 signaling pathways.

Three-Dimensional Spirothienoquinoline-Based Small Molecules for Organic Photovoltaic and Organic Resistive Memory Applications

A new electron-rich spirothienoquinoline unit, ^tBuSAF-Th, has been developed via incorporation of a thienyl unit instead of a phenyl unit into the six-membered ring of the spiroacridine (SAF) and utilized for the first time as a building block for constructing small-molecule electron donors in organic solar cells (OSCs) and as active layers in organic resistive memory devices. The resulting three-dimensional spirothienoquinoline-containing 1-4 exhibit high-lying highest occupied molecular orbital (HOMO) energy levels. By the introduction of electron-deficient benzochalcogenodiazole linkers, with the chalcogen atoms being varied from O to S and Se, a progressively lower lowest unoccupied molecular orbital (LUMO) energy level has been achieved while keeping the HOMO energy levels similar. This strategy has allowed an enhanced light-harvesting ability without compromising open-circuit voltage (V_oc) in vacuum-deposited bulk heterojunction OSCs using 1-4 as donors and C₇₀ as the acceptor. Good photovoltaic performances with power conversion efficiencies (PCEs) of up to 3.86% and high short-circuit current densities (J_sc) of up to 10.84 mA cm^-2 have been achieved. In addition, organic resistive memory devices fabricated with these donor-acceptor small molecules exhibit binary logic memory behaviors with long retention times and high on/off current ratios. This work indicates that the spirothienoquinoline moiety is a potential building block for constructing multifunctional organic electronic materials.

Reduced Energy Loss in Non-Fullerene Organic Solar Cells with Isomeric Donor Polymers Containing Thiazole π-Spacers

Large energy loss is one of the key factors that limit the power conversion efficiency (PCE) of organic solar cells (OSCs). In this work, we report reduced energy losses of OSCs via introducing thiazole π-spacers with different orientations to replace the thiophene π-spacers of the prototype polymer PBDB-T. The newly formed thiazole-containing isomeric polymers, PBDBTz-2 and PBDBTz-5, exhibited blue-shifted absorption and deeper lying energy levels compared to PBDB-T. When blended with IT-4F, the two polymers realized PCEs of 10.4% for PBDBTz-2 and 9.6% for PBDBTz-5, respectively, which were higher than that of PBDB-T (PCE = 9.3%). More critically, considerable open-circuit voltage (V_oc) enhancements were achieved by PBDBTz-2 and PBDBTz-5, which were 0.14 and 0.21 V higher than that of PBDB-T. A detailed analysis showed that the reduced energy loss resulted from the lower radiative recombination below the band gap and nonradiative recombination loss. This study demonstrated that the introduction of thiazole π-spacers with different orientations is effective to reduce the energy losses of OSCs, which provided valuable inspirations for the development of new conjugated polymers to the efficiency breakthrough of OSCs in future.

Does online learning work better than offline learning in undergraduate medical education? A systematic review and meta-analysis

With the increasing use of technology in education, online learning has become a common teaching method. How effective online learning is for undergraduate medical education remains unknown. This article's aim is to evaluate whether online learning when compared to offline learning can improve learning outcomes of undergraduate medical students. Five databases and four key journals of medical education were searched using 10 terms and their Boolean combinations during 2000-2017. The extracted articles on undergraduates' knowledge and skill outcomes were synthesized using a random effects model for the meta-analysis.16 out of 3,700 published articles were identified. The meta-analyses affirmed a statistically significant difference between online and offline learning for knowledge and skill outcomes based on post-test scores (SMD = 0.81; 95% CI: 0.43, 1.20; p < 0.0001; n = 15). The only comparison result based on retention test scores was also statistically significant (SMD = 4.64; 95% CI: 3.19, 6.09; p < 0.00001). The meta-analyses discovered no significant difference when using pre- and post-test score gains (SMD = 3.03; 95% CI: -0.13, 4.13; p = 0.07; n = 3). There is no evidence that offline learning works better. And compared to offline learning, online learning has advantages to enhance undergraduates' knowledge and skills, therefore, can be considered as a potential method in undergraduate medical teaching.

Oxidative Stability of Stripped Soybean Oil during Accelerated Oxidation: Impact of Monoglyceride and Triglyceride-Structured Lipids Using DHA as sn-2 Acyl-Site Donors

The current work aimed to clarify the effects of four structured lipids, including monoglycerides with docosahexaenoic acid (2D-MAG), diacylglycerols with caprylic acid (1,3C-DAG), triglyceride with caprylic acid at sn-1,3 and DHA at sn-2 position (1,3C-2D-TAG) and caprylic triglyceride on the oxidative stability of stripped soybean oil (SSO). The results revealed that compared to the blank group of SSO, the oxidation induction period of the sample with 2 wt% 2D-MAG and that with 1,3C-DAG were delayed by 2-3 days under accelerated oxidation conditions (50 °C), indicating that 2D-MAG and 1,3C-DAG prolonged the oxidation induction period of SSO. However, the inhibitory effect of α-tocopherol on SSO oxidation was reduced by 2D-MAG after addition of 2D-MAG to SSO containing α-tocopherol. 2D-MAG exhibited different antioxidative/pro-oxidative effects in the added/non-added antioxidants system. Compared to caprylic triglyceride, DHA at the sn-2 acyl site induced oxidation of structured lipids, thus further promoting the oxidation of SSO. The antioxidant was able to inhibit not only the oxidation of DHA in the SSO, but also the transesterification of sn-2 DHA to sn-1/sn-3 DHA in the structured lipid.

Does academic interest play a more important role in medical sciences than in other disciplines? A nationwide cross-sectional study in China

BACKGROUND

Research examining the effects of academic interest on students learning achievement across various disciplines, especially a comparison of the effects of academic interest between medical sciences and other disciplines, is still scarce. This study addressed this gap by answering 'does academic interest play a more important role in medical sciences than in other disciplines?'.

METHODS

A retrospective cross-sectional study, based on a large project of the National Undergraduate Student Development Survey (NUSDS) conducted by the Ministry of Education of China and Peking University in 2014, was designed to explore the role of academic interest in medical sciences and other disciplines. The participants were resampled to better represent the national distribution of undergraduate students in terms of their demographic characteristics. Specifically, survey data from 54,398 undergraduate students from 87 Chinese universities and colleges were used to address our research questions. We then used the propensity score matching (PSM) model to estimate the effect of academic interest on academic achievement and to compare the effects across different disciplines.

RESULTS

Academic interest had a significant positive impact on academic performance, with an effect size of 2.545 (p = 0.000). Specifically, the effect sizes for the disciplines of medical sciences, humanities, social sciences, natural sciences and engineering were 2.310 (p = 0.000), 2.231 (p = 0.000), 2.016 (p = 0.000), 3.840 (p = 0.000) and 2.698 (p = 0.000), respectively. The results show that no particular academic interest in medical sciences is needed to achieve academic success when compared with natural sciences and engineering programmes, but success in medical sciences requires more academic interest than success in humanities or social sciences.

CONCLUSIONS

This study clarifies the effect of academic interest on undergraduates' academic achievement while controlling for their demographic characteristics and family factors. The results provide insights into the role of academic interest in academic performance across various disciplines and can inform the college admissions practices of both institutions and high school students in China.

Effects of Spirulina algae as a feed supplement on nutritional value and flavour components of silkie hens eggs

OBJECTIVE

Silkie chicken (Gallus gallus domesticus brisson) is also named Chinese Taihe chicken, characterized by blue comb, green earlobes, black skin, meat and bones. This study aimed to evaluate the effects of spirulina feeding on the nutritive value and flavour of silkie hens eggs.

METHODS

A total of 280 Silkie hens of 42 weeks old were fed 4 different diets, including basal diet and basal diet containing 0.1%, 0.3% and 0.5% spirulina. Each diet group was divided into 70 Silkie hens experimentally. The production performance of silkie hens, the nutritional compositions [e.g., amino acids (AAs) and fatty acids] and flavour substances of silkie hens eggs were compared with control.

RESULTS

A 0.3% and 0.5% spirulina feeding significantly increased the average egg production rate and average egg weight, while only 0.3% spirulina feeding decreased both the average daily feed intake and feed conversion ratio of silkie hens compared with the controls (p < 0.05). The contents of crude protein, fat, cholesterol and Ca in silkie hens eggs were significantly increased by 0.3% spirulina feeding (p < 0.05). Only fat and cholesterol were significantly increased by 0.5% spirulina but had no significant difference compared with 0.3% spirulina. The flavour, amino acids/total AAs, and saturated fatty acids/unsaturated fatty acids in silkie hens eggs were significantly increased by 0.3% spirulina feeding than other groups (p < 0.05). A total of 46 volatile substances were identified in silkie hens eggs, and the substances of total acids, alkanes and aldehydes were significantly increased by 0.3% spirulina feeding.

CONCLUSION

Spirulina feeding at a proportion of 0.3% improved the production performance of silkie hens, and nutritive value and flavour of silkie hens eggs.

Analysis of volatile compounds in pork from four different pig breeds using headspace solid-phase micro-extraction/gas chromatography-mass spectrometry

PURPOSE

The volatile compounds that contribute to the flavor of pork are unknown. Therefore, the present study aimed to determine the differences in volatile compounds from pork meats of four different pig breeds using headspace solid-phase micro-extraction (HS-SPME)/gas chromatography-mass spectrometry (GC-MS).

METHODS

Piglets from four breeds (8/breed) (crossbred Ziwuling Sus scrofa [SUS] and purebreds Bamei pig [BAM], American Yorkshire pig [YOK], and Hezuo pig [HZP]) were selected. Characteristics of meat were measured. HS-SPME/GC-MS were used to analyze the volatile compounds of the meats.

RESULTS

The tenderness, taste, succulence, and broth flavor of the BAM and HZP were good. One hundred and eight volatile compounds with known molecular formulas were identified in BAM, 106 in SUS, 98 in YOK, and 98 in HZP. Sixty-four common volatile compounds were found in all four breeds. The highest relative amount of volatile compounds was found in the BAM. The compounds which may contribute to the flavor of pork were 3-methyl-1-butanol, 1-nonanal, octanal, hexanal, 2-pentyl-furan, 1-penten-3-one, N-morpholinomethyl-isopropyl-sulfide, methyl butyrate, and (E,E)-2, 4-decadienal.

CONCLUSION

The volatile compounds in pork belong to several classes, and the highest relative amount of volatile compounds was found in BAM.

Manipulate Micrometer Surface and Nanometer Bulk Phase Separation Structures in the Active Layer of Organic Solar Cells via Synergy of Ultrasonic and High-Pressure Gas Spraying

For organic solar cells, the vertical and lateral micro-/nanometer-scale structure in the active layer largely determines the device performance. In this work, the surface and bulk domain size of the photoactive layer are successfully manipulated with a facile two-step spraying method, that is, an ultrathin active layer by high-pressure spraying is deliberately stacked on top of the thick active layer by ultrasonic spraying. Thus, the morphology is effectively optimized with the comprehensive study of optical and electrical characteristics, such as photon absorption, exciton dissociation efficiency, and bimolecular recombination. Moreover, the novel method can be used not only in the fullerene system but also in the nonfullerene system, demonstrating the remarkable universality through this synergy method. This work provides an easy and reliable strategy to improve photovoltaic device performance in the industrial large-area spray-coating process.

13%-Efficiency Quaternary Polymer Solar Cell with Nonfullerene and Fullerene as Mixed Electron Acceptor Materials

In this article, we report 13%-efficiency quaternary polymer solar cell. By introducing bis-PC₇₁BM:PC₇₁BM into a known nonfullerene system-poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl))benzo[1,2- b:4,5- b']dithiophene)- co-(1,3-di(5-thiophene-2-yl)-5,7-bis(2-ethylhexyl)benzo[1,2- c:4,5- c']dithiophene-4,8-dione):3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone-methyl))-5,5,11,11-tetrakis(4- n-hexylphenyl)-dithieno[2,3 d:2',3' d']- s-indaceno[1,2 b:5,6 b']dithiophene (PBDB-T:IT-M), the quaternary solar cell significantly outperforms the nonfullerene binary and the ternary (PBDB-T:IT-M:fullerene) devices with a significant increase in the short-circuit current-density (18.2 vs 16.5 and 16.8-17.5 mA/cm²) and the fill factor (0.73 vs 0.67 and 0.707-0.726), and hence, large power conversion efficiency (13% for quaternary vs 11% for the binary and 12% for the ternary). Grazing incidence wide-angle X-ray scattering data indicate that both the polymer and IT-M phase crystallinity becomes greater upon introduction of PC₇₁BM as the forth additive into the host ternary PBDB-T:IT-M:bis-PC₇₁BM, which results in an increase in both the electron and hole mobilities, contributing to the J_sc enhancement. Our results indicate that the use of the forth fullerene component provides more choices and more mechanisms than the ternary systems for tuning the photon-to-electron conversion; therefore, sheds light on the realization of high-efficiency polymer solar cells by designing the multiacceptor components with aligned energy levels, complementary absorption spectra, and improved film morphologies.

Systematically investigating the influence of inserting alkylthiophene spacers on the aggregation, photo-stability and optoelectronic properties of copolymers from dithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene and benzothiadiazole derivatives

PDTBDT-SBT and PDTBDT-SFBT presented a superior trade-off between band gaps and photo-stabilities.