Asymmetric Wide-Bandgap Polymers Simultaneously Improve the Open-Circuit Voltage and Short-Circuit Current for Organic Photovoltaics.

A trade-off between open-circuit voltage (V OC ) and high short-circuit (J SC ) becomes one of the most vital problems limiting further improvement in polymer solar cells' (PSCs) efficiency. In this work, two asymmetric polymer donors PBDT-F-2TC and PBDT-SF-2TC are designed and synthesized. When blended with a state-of-the-art acceptor IT-4F with low lowest-unoccupied molecular orbital level, simultaneously high V OC (up to 0.94 V) and J SC (up to 20.73 mA cm-2 ) are obtained for both copolymers. Note that the V OC value of 0.94 V is the highest value of PSCs based on IT-4F reported so far. The simultaneously improved V OC and J SC in resulting devices are discovered from the deep highest-occupied molecular orbital levels (-5.5 to -5.7 eV) and the hyperchromic effect of the polymers, the small driving force, and the small energy loss during the charge transfer, due to the synergistic effect of asymmetric carboxylate unit and fluorine/sulfur atoms. More importantly, thanks to the asymmetric 2TC, both PBDT-F-2TC- and PBDT-SF-2TC-based PSCs can be successfully processed by non-halogenated solvent 1,2,4-trimethylbenzene (TMB) to yield device efficiencies of 10.29% and 10.39%, respectively, which are the maximum values for non-fullerene PSCs fabricated using the eco-friendly solvent TMB.

Velocity measurement based on multiple self-mixing interference.

This study proposes a novel algorithm based on the multiple self-mixing interference (MSMI) theory to measure the velocity of a remote target without contact. The principle of MSMI is presented and the corresponding formulas for velocity measurement are derived. Fast Fourier transform is applied to detect signal frequency and calculate velocity values. A low-cost, compact, and easy-to-operate experimental setup is also constructed. Experiments are conducted to validate the correctness of our algorithm. This algorithm can improve resolution more easily than conventional self-mixing interference methods.

Relationship between chromatin configuration and in vitro maturation ability in guinea pig oocytes.

BACKGROUND: Germinal vesicle (GV) chromatin configurations of oocytes are proposed to be related to oocyte competence and may reflect the quality of oocyte. Currently, a limited number of published studies investigated the GV chromatin configurations of guinea pig oocytes. OBJECTIVE: In this study on the in vitro maturation (IVM) of guinea pig oocytes, we examined the changes in their GV chromatin configurations during meiotic progression. METHODS: Based on the degree of chromatin compaction, the GV chromatin configurations of guinea pig oocytes could be divided into three categories depending on whether the nucleolus-like body (NLB) was surrounded or partly surrounded by compacted chromatin, namely the uncondensed (NSN), the intermediate type (SN-1) and the compacted type (SN-2). RESULTS: The percentage of cells displaying the SN-2 configuration increased with the growth of guinea pig oocytes, suggesting that this configuration presents the potential for maturation in oocytes. Oocytes derived from larger follicle exhibited increased meiotic potential. Serum starvation affected the GV chromatin configurations of guinea pig oocytes. CONCLUSIONS: Collectively, these results suggest that the SN-2 type might be a more mature form of configuration in guinea pig oocyte, whose proportion was associated with the follicle size and susceptible to the environment (e.g. serum concentration).