Transparent Perovskite Light-Emitting Touch-Responsive Device

A light-emitting touch-responsive device (LETD) for instantaneous visualization of pressure mapping is reported. The LETD integrates an organometal halide perovskite polymer composite emissive layer and a flexible silver nanowire polyurethane composite transparent electrode. The composite emissive layer contains methylammonium lead bromide nanocrystals uniformly dispersed in a poly­(ethylene oxide) (PEO) matrix and emits an intense green luminescence that peaks at 529 nm. The PEO matrix promotes the formation of small perovskite grains (∼20 nm) and a pinhole-free composite film with surface roughness of only 2.96 nm. The composite transparent electrode is separated from the emissive layer with a 100 μm thick spacer. When a local pressure is applied, a Schottky contact is formed instantaneously between the metal and the emissive layer, and electroluminescence is produced at voltages as low as 2.5 V and reaches 1030 cd/m² at 6 V. The transparent LETD has approximately 68% transparency. It can be bent to a 6 mm radius when polyethylene terephthalate is used as the substrate. The perovskite LETD has fast response and can be pixelated to offer potential applications in robotics, motion detection, fingerprint devices, and interactive wallpapers

Transparent Perovskite Light-Emitting Touch-Responsive Device

A light-emitting touch-responsive device (LETD) for instantaneous visualization of pressure mapping is reported. The LETD integrates an organometal halide perovskite polymer composite emissive layer and a flexible silver nanowire polyurethane composite transparent electrode. The composite emissive layer contains methylammonium lead bromide nanocrystals uniformly dispersed in a poly­(ethylene oxide) (PEO) matrix and emits an intense green luminescence that peaks at 529 nm. The PEO matrix promotes the formation of small perovskite grains (∼20 nm) and a pinhole-free composite film with surface roughness of only 2.96 nm. The composite transparent electrode is separated from the emissive layer with a 100 μm thick spacer. When a local pressure is applied, a Schottky contact is formed instantaneously between the metal and the emissive layer, and electroluminescence is produced at voltages as low as 2.5 V and reaches 1030 cd/m² at 6 V. The transparent LETD has approximately 68% transparency. It can be bent to a 6 mm radius when polyethylene terephthalate is used as the substrate. The perovskite LETD has fast response and can be pixelated to offer potential applications in robotics, motion detection, fingerprint devices, and interactive wallpapers

Electrolyte-Gated Red, Green, and Blue Organic Light-Emitting Diodes

We report vertical electrolyte-gated red, green, and blue phosphorescent small-molecule organic light-emitting diodes (OLED), in which light emission was modified by tuning the electron injection via electrochemical doping of the electron injection layer 4,4-bis­(<i>N</i>-carbazolyl)-1,1-biphenyl (CBP) under the assistance of a polymer electrolyte. These devices comprise an electrolyte capacitor on the top of a conventional OLED, with the interfacial contact between the electrolyte and electron injection layer CBP of OLEDs achieved through a porous cathode. These phosphorescent OLEDs exhibit the tunable luminance between 0.1 and 10 000 cd m^–2, controlled by an applied bias at the gate electrode. This simple device architecture with gate-modulated luminance provides an innovative way for full-color OLED displays

Silver Nanowire Percolation Network Soldered with Graphene Oxide at Room Temperature and Its Application for Fully Stretchable Polymer Light-Emitting Diodes

Transparent conductive electrodes with high surface conductivity, high transmittance in the visible wavelength range, and mechanical compliance are one of the major challenges in the fabrication of stretchable optoelectronic devices. We report the preparation of a transparent conductive electrode (TCE) based on a silver nanowire (AgNW) percolation network modified with graphene oxide (GO). The monatomic thickness, mechanical flexibility, and strong bonding with AgNWs enable the GO sheets to wrap around and solder the AgNW junctions and thus dramatically reduce the inter-nanowire contact resistance without heat treatment or high force pressing. The GO-soldered AgNW network has a figure-of-merit sheet resistance of 14 ohm/sq with 88% transmittance at 550 nm. Its storage stability is improved compared to a conventional high-temperature annealed AgNW network. The GO-soldered AgNW network on polyethylene terephthalate films was processed from solutions using a drawdown machine at room temperature. When bent to 4 mm radius, its sheet resistance was increased by only 2–3% after 12 000 bending cycles. GO solder can also improve the stretchability of the AgNW network. Composite TCE fabricated by inlaying a GO-soldered AgNW network in the surface layer of polyurethane acrylate films is stretchable, by greater than 100% linear strain without losing electrical conductivity. Fully stretchable white polymer light-emitting diodes (PLEDs) were fabricated for the first time, employing the stretchable TCE as both the anode and cathode. The PLED can survive after 100 stretching cycles between 0 and 40% strain and can be stretched up to 130% linear strain at room temperature