A solar-driven CO2 reduction (CO2R) cell was constructed, consisting of a tandem GaAs/InGaP/TiO2/Ni photoanode in 1.0 M KOH­(aq) (pH = 13.7) to facilitate the oxygen-evolution reaction (OER), a Pd/C nanoparticle-coated Ti mesh cathode in 2.8 M KHCO3(aq) (pH = 8.0) to perform the CO2R reaction, and a bipolar membrane to allow for steady-state operation of the catholyte and anolyte at different bulk pH values. At the operational current density of 8.5 mA cm–2, in 2.8 M KHCO3(aq), the cathode exhibited <100 mV overpotential and >94% Faradaic efficiency for the reduction of 1 atm of CO2(g) to formate. The anode exhibited a 320 ± 7 mV overpotential for the OER in 1.0 M KOH­(aq), and the bipolar membrane exhibited ∼480 mV voltage loss with minimal product crossovers and >90 and >95% selectivity for protons and hydroxide ions, respectively. The bipolar membrane facilitated coupling between two electrodes and electrolytes, one for the CO2R reaction and one for the OER, that typically operate at mutually different pH values and produced a lower total cell overvoltage than known single-electrolyte CO2R systems while exhibiting ∼10% solar-to-fuels energy-conversion efficiency.

Solution-processed nickel oxides (s-NiO x ) are used as hole injection and transport layers in solution-processed organic light-emitting diodes (OLEDs). By increasing the annealing temperature, the nickel acetate precursor fully decomposes and the s-NiO x film shows larger crystalline grain sizes, which lead to better hole injection and transport properties. UV−ozone treatment on the s-NiO x surface is carried out to further modify its surface chemistry, improving the hole injection efficiency. The introduction of more dipolar species of nickel oxyhydroxide (NiO(OH)) is evidenced after the treatment. Dark injection−space charge limited (DI−SCL) transient measurement was carried out to compare the hole injection efficiency of s-NiO x and poly(3,4-ethylenedioxythiophene):poly-(styrenesulfonate) (PEDOT:PSS) hole injection layers (HIL). The UV−ozone treated s-NiO x shows significantly better hole injection, with a high injection efficiency of 0.8. With a p-type thin film transistor (TFT) configuration, the high-temperature annealed s-NiO x film shows a hole mobility of 0.141 cm 2 V −1 s −1 , which is significantly higher compared to conventional organic hole transport layers (HTLs). Because of their improved hole injection and transport properties, the solution-processed phosphorescent green OLEDs with NiO x HIL/HTL show a maximum power efficiency of 75.5 ± 1.8 lm W −1 , which is 74.6 + 2.1% higher than the device with PEDOT:PSS HIL. The device with NiO x HIL/HTL also shows a better shelf stability than the device with PEDOT:PSS HIL. The NiO x HIL/HTL is further compared with PEDOT:PSS HIL/N,N′-Di(1-naphthyl)-N,N′diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) HTL in the thermal-evaporated OLEDs. The device with NiO x HIL/HTL shows a comparable efficiency at high electroluminescence (EL) intensities.

Nanotransducer-impregnated self-organized helical superstructures are found to exhibit unprecedented reversible handedness inversion upon irradiation by the dual-wavelength near-infrared light. Upon near-infrared laser irradiation at 808 nm, the helical twist sense changes from right-handed to left-handed through an achiral liquid-crystal phase, whereas its reverse process occurs upon the near-infrared laser irradiation at 980 nm.