Fei Xiu

One-step and green synthesis of nitrogen-doped carbon quantum dots for multifunctional electronics

A facile one-step and green synthesis method was developed to prepare water soluble, environmentally friendly, and highly nitrogen-doped carbon quantum dots (CQDs) with tunable properties. As a proof-of-concept application, a multifunctional electronic device with the configuration of PEDOT:PSS/s-CQD@SWCNT/PEDOT:PSS was fabricated through a full-solution process, which exhibits memory and current limiting behavior, with the merit of stable operation and reliable endurance.

Transient Light Emitting Devices Based on Soluble Polymer Composites

Building transient electronics are promising and emerging strategy to alleviate the pollution issues from electronic waste (e-waste). Although a variety of transient devices comprising organic and inorganic materials have been described, transient light emitting devices are still elusive but highly desirable because of the huge amount of lighting and display related consumer electronics. Here we report a simple and efficient fabrication of large-area flexible transient alternating current electroluminescent (ACEL) device through a full-solution processing method. Using transparent flexible AgNW-polymer as both electrodes, the devices exhibit high flexibility and both ends side light emission, with the features of controlled size and patterned structure. By modulating the mass ratio of blue and yellow phosphors, the emission color is changed from white to blue. Impressively, the fabricated ACEL device can be thoroughly dissolved in water within 30 min. Our strategy combining such advances in transient light emitting devices with simple structure, widely used materials, full solution process, and high solubility will demonstrate great potential in resolving the e-waste from abandoned light-emitting products and expand the opportunities for air-stable flexible light emitting devices.

Large-area patterned 2D conjugated microporous polymers via photomask-assisted solid-state photopolymerization

The large-area and scalable patterning process of conjugated polymers is a critical step toward their practical applications in organic electronics. Here we report a wafer-scale patterning method for 2D conjugated microporous polymer (CMP) films on arbitrary substrates via photomask-assisted solid-state photopolymerization under ambient conditions. 2D CMP patterns from monomeric carbazole materials were controllably prepared with variable geometries with the geometric photomasks and desired film thicknesses by modulating the polymerization time. Moreover, 2D CMP patterns with various size and shapes can be formed onto a reduced graphene oxide (rGO) substrate to construct 2D CMP/rGO heterostructures. The obtained heterostructure exhibited a p-type behavior compared to the metal-like property of the rGO film. Combining this solid-state photopolymerization with photomask techniques, a patterned 2D organic/inorganic heterostructure with a precise size and shape control could be further realized for other 2D materials and their integrated devices.

Micro-supercapacitors based on oriented coordination polymer thin films for AC line-filtering

Reported herein is a facile solution-processed substrate-independent approach for preparation of oriented coordination polymer (Co-BTA) thin-film electrodes for on-chip micro-supercapacitors (MSCs). The Co-BTA-MSCs exhibited excellent AC line-filtering performance with an extremely short resistance–capacitance constant, making it capable of replacing aluminum electrolytic capacitors for AC line-filtering applications.

Polymer–carbon dot hybrid structure for a self-rectifying memory device by energy level offset and doping

A strategy for self-rectifying memory diodes based on a polymer–carbon dot hybrid structure, with a configuration of rGO/PEDOT : PSS/carbon dots/MEH-PPV/Al, has been proposed. The fabricated device exhibits a rectification of 103 in the rectification model and an ON/OFF current ratio of 121 in the memory model. The rectifying behavior was attributed to an energy level offset between the electrodes and the bilayer polymers and the memory effect was induced by carrier trapping of carbon dots within the polymers.

Cathodic shift of a photo-potential on a Ta3N5 photoanode by post-heating a TiO2 passivation layer

Ta3N5 is a promising photoanode material for solar water splitting due to its suitable band gap and high theoretical solar energy conversion. A high onset potential of Ta3N5 limits its photoelectrochemical performance due to serious surface charge recombination. In a previous study, a TiO2 passivation layer was usually coated on the surface of Ta3N5 to reduce the surface recombination and improve the performance of a sample. However, to date, there are no studies on the effect of conductivity of the TiO2 passivation layer on the photoelectrochemical properties of a Ta3N5 photoanode. In this work, for the first time, the conductivity of TiO2 is increased by post-heating of a TiO2 passivation layer, leading to a 90 mV cathodic shift of the photo-potential of Ta3N5. After further loading with a Ni(OH)x/FeOOH bi-layer electrocatalyst, the Ta3N5 photoanode achieves a current density of 6.4 mA cm−2 at 1.23 VRHE and a HC-STH (half-cell solar to hydrogen efficiency) of 0.72% under a sunlight simulator (100 mW cm−2), which are the highest values among the Ta3N5 photoanodes prepared by thermal oxidation and nitridation of Ta foil.