To reduce interface loss between optical fibers and devices in telecommunication systems, the development of an optical-fiber-based device that can be fused directly with fibers is important. A novel optical modulator consisting of a bare fiber core surrounded by magnetic fluids instead of by a SiO2 cladding layer is proposed. Applying a magnetic field raises the refractive index of the magnetic fluid. Thus we can control the occurrence of total reflection at the interface between the fiber core and the magnetic fluid when light propagates along the fiber. As a result, the intensity of the outgoing light is modulated by variation in field strength. Details of the design, fabrication, and working properties of such a modulator are presented.

A continuous roll-to-roll compatible blade-coating method for multi-layers of general organic semiconductors is developed. Dissolution of the underlying film during coating is prevented by simultaneously applying heating from the bottom and gentle hot wind from the top. The solvent is immediately expelled and reflow inhibited. This method succeeds for polymers and small molecules. Uniformity is within 10% for 5 cm by 5 cm area with a mean value of tens of nanometers for both organic light-emitting diode (OLED) and solar cell structure with little material waste. For phosphorescent OLED 25 cd/A is achieved for green, 15 cd/A for orange, and 8 cd/A for blue. For fluorescent OLED 4.3 cd/A is achieved for blue, 9 cd/A for orange, and 6.9 cd/A for white. For OLED with 2 cm by 3 cm active area, the luminance variation is within 10%. Power conversion efficiency of 4.1% is achieved for polymer solar cell, similar to spin coating using the same materials. Very-low-cost and high-throughput fabrication of efficient organic devices is realized by the continuous blade-only method.

Structural evolution along the edges of magnetic fluid microstrips under external magnetic fields is investigated in this article. It was found that when the external magnetic field increased the structure evolves from an originally monodispersed state to a disordered column state, and then to several levels of ordered structures. For the ordered structure state, a one-dimensional periodic structure resulted under lower field strengths, and with an increase in field strength, more columns formed. Hence, a two-dimensional ordered array of columns was achieved. Further experimental results showed that the ordered structure can be manipulated by adjusting control parameters, such as field strength, sweep rate, fluid concentration, strip width, and strip thickness. These results lay the groundwork for utilizing controllable ordered structures in magnetic fluid microstrips to develop potential applications, such as photonic crystals or waveguides.

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The ultraviolet (UV) radiation in the solar spectrum causes most of the decay under sunlight for solar cells based on organic photovoltaics (OPV). One‐year outdoor lifetime still remains challenging for OPV. The lifetime of 2000 h under continuous laboratory light corresponds to a 1 year outdoor lifetime. Herein, the stability of the OPVs is studied under continuous irradiation by a UV light emitting diode of 365 nm with a long tracking time. The intensity of 50 W m−2 is the same as the sunlight UV. The compositions of the active layer and cathode interfacial layer are sensitive to UV irradiation. In general, ternary devices have better UV stability than binary devices. In particular, a good stability is achieved for the ternary device based on the high‐performance blend with poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl‐3‐fluoro)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b']dithiophene))‐alt‐(5,5‐(1',3'‐di‐2‐thienyl‐5',7'‐bis(2‐ethylhexyl)benzo[1',2'‐c:4',5'‐c']dithiophene‐4,8‐dione)] (PM6) as the donor. The acceptor is 2,2'‐((2Z,2'Z)‐((12,13‐bis(2‐ethylhexyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2",3":4',5']thieno[2',3':4,5]pyrrolo[3,2‐g]thieno[2',3':4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (Y6). The fullerene derivative [6,6]‐phenyl C71‐butyric acid methyl ester (PC71BM) is added as the second acceptor, whereas a polymer poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b']dithiophene))‐co‐(1,3‐di(5‐thiophene‐2‐yl)‐5,7‐bis(2‐ethylhexyl)benzo[1,2‐c:4,5‐c']dithiophene‐4,8‐dione)] (PBDB‐T) is added as the second donor. For the PM6:Y6 ternary device, the UV half lifetime is 1750 h, which is close to the 2000 h target set by the outdoor of a 1 year lifetime.