UV-Cross-linkable Donor-Acceptor Polymers Bearing a Photostable Conjugated Backbone for Efficient and Stable Organic Photovoltaics.

High-performance photovoltaic polymers bearing cross-linkable function together with a photorobust conjugated backbone are highly desirable for organic solar cells to achieve both high device efficiency and long-term stability. In this study, a family of such polymers is reported based on poly[(2,5-bis(2-hexyldecyloxy)phenylene)- alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[ c]-[1,2,5]thiadiazole)] (PPDT2FBT), a high-performance photovoltaic donor-acceptor polymer, with different contents of terminal vinyl-appended side chains for cross-linking. The polymers were named PPDT2FBT-V x and prepared by varying the feeding ratio ( x mol %, x = 0, 5, 10, and 15) of the vinyl-appended monomer in polymerization. It was found that the vinyl integration did not sacrifice the original high photovoltaic performance of the polymers, as evidenced by comparable average power conversion efficiencies (PCEs) (6.95, 7.02, and 7.63%) observed for optimized devices based on PPDT2FBT-V0, PPDT2FBT-V5, and PPDT2FBT-V10, respectively, in blending with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). Unlike thermal cross-linking that greatly reduced device efficiency, UV cross-linking has proven to be an effective way to achieve both high device efficiency and thermostability for PPDT2FBT-V10 solar cells. UV-cross-linked PPDT2FBT-V10 solar cells displayed an initial average PCE of 5.28% and almost no decrease upon heat treatment at 120 °C for 40 h. Morphology studies revealed that UV-cross-linking did not only alter initial nanophase separation but also suppressed morphology evolution by aggregation in bulk heterojunction blend films. Photo-cross-linking requires material photostability. It is therefore worthwhile to note that these polymers and their blends with PC71BM were found to be extremely photostable, even upon continuous exposure to concentrated sunlight (up to 200 suns), and UV-cross-linking does not hamper this photostability. Further studies found that the devices fabricated with the UV-cross-linked PPDT2FBT-V10/PC71BM active layer can endure continuous light exposure to a solar simulator without deteriorating their performance.

[Clinical effect modified Chevron osteotomy combined with lateral tissue loosening in treating mild-moderate hallux valgus through internal signal approach].

OBJECTIVE: To explore clinical effect of modified Chevron osteotomy combined with lateral tissue loosening for the treatment of mild-moderate hallux valgus through internal signal approach. METHODS: From July 2015 to June 2016, 26 patients with mild-moderate hallux valgus treated with modified Chevron osteotomy combined with lateral tissue loosening through internal signal approach, including 2 males and 24 females aged from 45 to 65 years old with an average of(54.6±4.8) years old;the courses of diseases ranged from 1 to 5 months with an average of (7.5±3.3) months. Hallux valgus angle(HVA), inter metatarsal angle(IMA) were measured at 12 months after operation, and AOFAS score was applied to evaluate clinical effect before and after operation. RESULTS: All incisions were healed at stage I. No incision occurred infection, metatarsal necrosis and recurrence of hallux valgus deformity. Two patients occurred skin numbness caused by musculocutaneous nerve injury. Twenty-six patients were followed up from 6 to 12 months with an average of(9.12±2.06) months. HVA, IMA were(30.01±3.71)°, (14.00±1.50)° before operation and(9.41±4.16)°, (7.00±0.60)° after operation, which had significant difference. There was statistical significance in AOFAS score before operation 54.77±9.59 and after operation 92.73±5.47, and 19 cases obtained excellent results and 7 moderate. CONCLUSIONS: Modified Chevron osteotomy combined with full thread headless pressure screw fixation and lateral tissue loosening for the treatment of mild-moderate hallux valgus has advantages of excellent exposure, simple operation, stable fixation, rapid recovery. Akin osteotomy with internal capsulorrhaphy were used with lateral loosening and could recover soft tissue balance between lateral and internal, and could receive satisfied clinical effects.

Interconnecting semiconducting molecules with non-conjugated soft linkers: a way to improve film formation quality without sacrifice in charge mobility.

The formation of high quality homogeneous active component films is essential to the fabrication of many organic optoelectronic devices, especially those having a large area module. However, most small molecule (SM) semiconductors are unable to achieve such a goal via solution processing because their large and rigid π-conjugated structures generally drive them to aggregate or crystallize into inhomogeneous domains in the process. In this work, a SM semiconductor (SM-DPP6T) based on a diketopyrrolopyrrole (DPP) center with three thiophene units on both sides encounters the same problem. However, when its molecules are interconnected with soft alkyl linkers and change into a poly(rod-coil) polymer, PRC-DPP6T, the problem is solved. Compared with SM-DPP6T, PRC-DPP6T can form a high quality homogeneous film with much better uniformity and coverage on silicon wafers by spin-coating. Moreover, the so-prepared PRC-DPP6T field-effect transistors displayed a much narrower performance distribution and comparable mobility when compared with those based on SM-DPP6T (0.17 vs. 0.15 cm2 V-1 s-1). These results demonstrate that the interconnection of SM semiconductor molecules with soft non-conjugated linkers is a promising way to improve film formation quality while keeping mobility intact.