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Summary There is an urgent demand for all-polymer organic solar cells (AP-OSCs) to gain higher efficiency. Here, we successfully improve the performance to 16.09% by introducing a small amount of BN-T, a B←N-type polymer acceptor, into the PM6:PY-IT blend. It has been found that BN-T makes the active layer, based on the PM6:PY-IT:BN-T ternary blend, more crystalline but meanwhile slightly reduces the phase separation, leading to enhancement of both exciton harvesting and charge transport. From a thermodynamic viewpoint, BN-T prefers to reside between PM6 and PY-IT, and the fraction of this fine-tunes the morphology. Besides, a significantly reduced nonradiative energy loss occurs in the ternary blend, along with the coexistence of energy and charge transfer between the two acceptors. The progressive performance facilitated by these improved properties demonstrates that AP-OSCs can possibly comparably efficient with those based on small molecule acceptors, further enhancing the competitiveness of this device type.

Summary High-performance n-type (electron-transporting or n-channel) polymer semiconductors are critical components for the realization of various organic optoelectronic devices and complementary circuits, and recent progress has greatly advanced the performance of organic thin-film transistors, all-polymer solar cells, and organic thermoelectrics, to cite just a few. This Perspective focuses on the recent development of high-performance n-type polymer structures, particularly those based on the most investigated and novel electron-deficient building blocks, as well as summarizes the performance achieved in the above devices. In addition, this Perspective offers our insights into developing new electron-accepting building blocks and polymer design strategies, as well as discusses the challenges and opportunities in advancing n-type device performance.

Summary Generally, it is important to fine-tune the energy levels of donor and acceptor materials in the field of polymer solar cell (PSCs) to achieve a minimal highest occupied molecular orbital (HOMO) energy offset, which yet is still sufficient for charge separation. Based on the high-performance small-molecule acceptor (SMA) of BTP-4F, we modified the end groups of BTP-4F from IC-2F to CPTCN-Cl. It was found that when both end groups were substituted by CPTCN-Cl, the energy level upshift was too large that caused unfavorable energetic alignment, thus poor device performance. By using the strategy of asymmetric end groups, we were able to achieve near optimal energy level match, resulting in higher open-circuit voltage (VOC) and power conversion efficiency (PCE) compared with those given by the PM6:BTP-4F system. Our strategy can be useful and potentially applied to other material systems for maximizing efficiency of non-fullerene PSCs.

Drug resistance is a major challenge in the treatment of epilepsy. Drug-resistant epilepsy (DRE) accounts for 30% of all cases of epilepsy and is a matter of great concern because of its uncontrollability and the high burden, mortality rate, and degree of damage. At present, considerable research has focused on the development of predictors to aid in the early identification of DRE in an effort to promote prompt initiation of individualized treatment. While multiple predictors and risk factors have been identified, there are currently no standard predictors that can be used to guide the clinical management of DRE. In this review, we discuss several potential predictors of DRE and related factors that may become predictors in the future and perform evidence rating analysis to identify reliable potential predictors.

High-performance polymer semiconductors generally should have wide absorption, good solution process-ability, and fine-tuned physicochemical properties in order to achieve satisfying photovoltaic performance. Herein, two new alkynyl-functionalized electron donor units, 3-alkyl-3′-alkynyl-2,2′-bithiophene (TRTRy) and 3-alkoxy-3′-alkynyl-2,2′-bithiophene (TORTRy), were invented through the combination of the alkynyl side chain with the alkyl or alkoxy side chain, respectively. Copolymerization of these bithiophenes with difluorobenzothiadiazole (ffBT) afforded polymers ffBT-TRTRy and ffBT-TORTRy, respectively. When applied into polymer solar cells (PSCs), devices using ffBT-TRTRy donor polymer display a maximum power conversion efficiency (PCE) of 2.34% with a short-circuit current (Jsc) of 7.46 mA cm−2, an open circuit voltage (Voc) of 0.93 V, and a fill factor (FF) of 34.0%. The TORTRy containing polymer ffBT-TORTRy affords PSCs with a much improved PCE of 6.60% with a higher Jsc of 15.09 mA cm−2, a larger FF of 58.3%, and a Voc of 0.75 V. The performance improvement of PSC devices using ffBT-TORTRy donor is mainly attributed to the simultaneous realization of higher Jsc and FF, while maintaining a good Voc. The results demonstrate that alkynyl-functionalized H-H bithiophenes are promising building blocks for efficient PSCs.

Compared to bulk heterojunction (BHJ) organic solar cells (OSCs) prepared by the blend casting in “one step process”, sequential deposition (SD) processed OSCs can realize an ideal profile of vertical component distribution due to the swelling of polymer films. Herein, we did trials on several kinds of second solvents for swelling the polymer layer, and investigated the packing structure and morphology of the swollen films and the performance of the resulting devices. We found that an optimized morphology can be achieved by solvent swelling while using orthodichlorobenzene (o-DCB) as the second layer processing-solvent, with polymer donor PffBT-3 as bottom layer, PC71BM as top layer and bicontinuous networks in the middle. Such solvent swelling process also makes the SD method exempt from thermal annealing treatment. The device based on SD yields a power conversion efficiency (PCE) up to 8.7% without any post-treatment, outperforming those from the devices based on SD using other solvents and that (7.06%) from BHJ device, respectively. We also extended the use of this approach to all-polymer blend system, and successfully improved the efficiency from 4.72% (chloroform) to 9.35% (o-DCB), which is among the highest PCEs in all-polymer-based OSCs fabricated with SD method. The results demonstrate that the swelling of the polymer by the second layer solvent is a necessity for SD, paving the way towards additive-free high-performance OSCs.