No abstract

Three small molecules named DR3TBDTT, DR3TBDTT-HD, and DR3TBD2T with a benzo[1,2-b:4,5-b']dithiophene (BDT) unit as the central building block have been designed and synthesized for solution-processed bulk-heterojunction solar cells. Power conversion efficiencies (PCEs) of 8.12% (certified 7.61%) and 8.02% under AM 1.5G irradiation (100 mW cm(-2)) have been achieved for DR3TBDTT- and DR3TBDT2T-based organic photovoltaic devices (OPVs) with PC71BM as the acceptor, respectively. The better PCEs were achieved by improving the short-circuit current density without sacrificing the high open-circuit voltage and fill factor through the strategy of incorporating the advantages of both conventional small molecules and polymers for OPVs.

A series of acceptor-donor-acceptor simple oligomer-like small molecules based on oligothiophenes, namely, DRCN4T-DRCN9T, were designed and synthesized. Their optical, electrical, and thermal properties and photovoltaic performances were systematically investigated. Except for DRCN4T, excellent performances were obtained for DRCN5T-DRCN9T. The devices based on DRCN5T, DRCN7T, and DRCN9T with axisymmetric chemical structures exhibit much higher short-circuit current densities than those based on DRCN6T and DRCN8T with centrosymmetric chemical structures, which is attributed to their well-developed fibrillar network with a feature size less than 20 nm. The devices based on DRCN5T/PC71BM showed a notable certified power conversion efficiency (PCE) of 10.10% under AM 1.5G irradiation (100 mW cm(-2)) using a simple solution spin-coating fabrication process. This is the highest PCE for single-junction small-molecule-based organic photovoltaics (OPVs) reported to date. DRCN5T is a rather simpler molecule compared with all of the other high-performance molecules in OPVs to date, and this might highlight its advantage in the future possible commercialization of OPVs. These results demonstrate that a fine and balanced modification/design of chemical structure can make significant performance differences and that the performance of solution-processed small-molecule-based solar cells can be comparable to or even surpass that of their polymer counterparts.

Displays are basic building blocks of modern electronics 1,2. Integrating displays into textiles 17 offers exciting opportunities for smart electronic textiles-the ultimate form of wearables 18 poised to change the way we interact with electronic devices 3-6. Display textiles serve to bridge human-machine interactions 7-9 , offering for instance, a real-time communication tool for individuals with voice or speech disorders. Electronic textiles capable of communicating 10 , sensing 11,12 and supplying electricity 13,14 have been reported previously. However, textiles 22 with functional, large-area displays have not been achieved so far because obtaining small illuminating units that are both durable and easy to assemble over a wide area is challenging. Here, we report a 6 m (L) × 25 cm (W) display textile containing 5×10 5 electroluminescent (EL) units narrowly spaced to ~800 μm. Weaving conductive weft and luminescent warp fibres forms micron-scale EL units at the weft-warp contact points. Brightness between EL units deviates by < 6.3% and remains stable even when the textile is bent, stretched or pressed. We attribute this uniform and stable lighting to the smooth luminescent coating around the 2 warp fibres and homogenous electric field distribution at the contact points. Our display textile is flexible and breathable and withstands repeatable machine-washing, making them suitable for practical applications. We show an integrated textile system consisting of display, 32 keyboard and power supply can serve as a communication tool, which could potentially drive 33 the Internet of Things in various areas including healthcare. Our approach unifies the 34 fabrication and function of electronic devices with textiles, and we expect weaving fibre 35 materials to shape the next-generation electronics.