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The difluorine and carboxylate substitutions can effectively down-shift the HOMO level of the donors, improved molecular face-on orientation and reduced energy loss.

To understand different control loops that have been proposed to improve the quality of current into grid from the perspective of output impedance, control-loop-based output impedance enhancement of grid-tied inverters for harmonic suppression is proposed in this paper. The principle and generalized control loop deduction are presented for reshaping the output impedance. Taking a traditional LCL (Inductor-Capacitor-Inductor)-type inverter with dual-loop control as an example, different kinds of control loop topologies are derived step by step and further optimized for the implementation of the proposed principle. Consequently, the improved control consists of a filtering-capacitor voltage loop, and a grid current loop is found which can remove the existing inner capacitor current loop and therefore simplify the control. Finally, the effectiveness of the proposed control method is compared with the existing method and both are verified by simulations and experiments.

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In this study, we explored the relationship between extracurricular (formal and informal) music activity participation and music and Chinese language academic achievements of primary school students in China. Fourth graders ( N = 10,958) reported their demographic information and extracurricular music activity participation, and completed two standardized academic achievement tests, one on music and another on the Chinese language. Results showed that students’ music activity participation was related to higher music academic achievement after controlling for gender, school location, and family socioeconomic status. The effect of students’ informal music activity participation on their music academic achievements was greater than that of students’ formal music activity participation. Remarkably, students’ informal music activity participation was also positively related to their Chinese language academic achievement, while formal music activity participation showed a negative correlation with academic achievement in Chinese language. Findings contributed to an increased understanding of the influence of different kinds of extracurricular music activities on students’ academic developments.

A deep highest occupied molecular orbital (HOMO) level is a prerequisite for polymer donor material to boost the organic solar cells (OSCs) performance by achieving high open circuit voltage (V oc ). Abandoning the traditional concept of donor−acceptor (D-A) structure, two copolymers PBTZ-4TC and PBTZ-C4T based on acceptor 1 -π-acceptor 2 (A 1 -π-A 2 ) architecture, where thiophene as the bridge, the difluorinated benzotriazole (BTZ) as A 1 unit alternating copolymerized with 4,4′dicarboxylate-substituted difluorotetrathiophene (4TC) and 3,3′-dicarboxylate-substituted difluorotetrathiophene (C4T) as A 2 , respectively, are developed. Because of the double acceptor blocks with high electron affinity, both A 1 -π-A 2 type copolymers possess the lower HOMO levels of 5.52−5.56 eV, which are lower than most D-A type donors. Polymer PBTZ-4TC and PBTZ-C4T have the same backbone but only differ with the position of carboxylate substituent on the A 2 unit. Intriguingly, subtle optimizing the position of the carboxylate-substitute causes a significantly difference on the properties of the A 1 -π-A 2 type copolymers. PBTZ-C4T with more planar geometry is demonstrated with better light absorption, higher crystallinity, more pronounced temperature-dependent aggregation effect, and favorable bulk heterojunction morphology but with slightly higher HOMO level and more emission energy loss relative to the PBTZ-4TC. The PBTZ-C4T device exhibits the higher power conversion efficiency (PCE) of 9.34% than the PBTZ-4TC-based one (8.75%). These results reveal that concept of A 1 -π-A 2 type copolymers not only can afford more flexibility in tuning the energy levels to achieve the deep HOMO levels but also can provide a facial strategy to greatly enrich the types of polymer donors for high-performance OSCs. KEYWORDS: organic solar cells, acceptor 1 -π-acceptor 2 (A 1 -π-A 2 ) copolymers, more planar geometry, deep energy level, high performance

Introducing electron‐withdrawing groups onto donor‐acceptor (D‐A) type conjugated materials is a commonly used method for lowering their highest occupied molecular orbital (HOMO) energy level to achieve higher open circuit voltage (Voc) in polymer solar cells (PSCs). However, this method is rather costly due to the tedious synthesis and low yield involved in preparing the target monomers. Here, a novel design concept of using two different acceptor units to construct acceptor1‐acceptor2 (A1‐A2) type polymers with a deep HOMO level is proposed. Two A1‐A2 type wide bandgap (WBG) polymers, PB24‐3TDC and PB68‐3TDC, were designed for PSCs. The developed polymers possess proper energy levels and complementary absorption with an efficient electron acceptor ITIC‐Th. More importantly, by slightly regulating the alkyl side‐chains, molecular stacking and photoluminescence (PL) emission energy loss of polymers can be alternated significantly. As a result, tuned Voc from 0.9 to 1.0 V and short‐circuit current (Jsc) from 9.4 to 17.0 mA cm−2 can be achieved. The device based on PB24‐3TDC:ITIC‐Th exhibits a higher power conversion efficiency (PCE) of 10.3% compared to PB68‐3TDC:ITIC‐Th based device with a PCE of 7.88%. These results show that the design concept of A1‐A2 type polymer donors have great potential for blending with non‐fullerene acceptors for achieving high performance PSCs.