Yannan Lu

Bio: Yannan Lu is an academic researcher from Charles Darwin University. The author has contributed to research in topics: Conductive polymer & Ionic liquid. The author has an hindex of 2, co-authored 5 publications receiving 10 citations. Previous affiliations of Yannan Lu include Nanjing Tech University.

Coordination polymers for n-type thermoelectric applications

Abstract: Coordination polymers (CPs) are potential thermoelectric (TE) materials to replace the sometimes costly, brittle and toxic heavy metal inorganic TEs for near-ambient-temperature applications. Air-stable and highly conductive p-type thermoelectric CPs are relatively well known, but the their n-type counterparts are only now emerging and both are needed for most practical applications. This perspective reviews recent advances in the development of n-type thermoelectric CPs, particularly the 1D and 2D metal bisdithiolenes, and introduces a relatively new class of guest@metal-organic framework(MOF)-based composites. Low dimensional CPs with reasonable n-type thermoelectric performance are emerging with good charge mobility and air-stability but still relatively low electrical conductivity.

Air-stable and low threshold amplified spontaneous emission via CsBr aqueous solution processed all-inorganic CsPbBr3 perovskite films

Abstract: Inorganic cesium lead halide perovskite (CsPbX3, X = Cl, Br, and I) has attracted increasing attention in the field of laser application due to its excellent stability compared to the organic–inorganic hybrid perovskite since affording the radiation of a long pulse pump source requires high thermal stability of the material. However, it is difficult to observe the amplified spontaneous emission (ASE) of CsPbBr3 using a one-step solution method due to the low solubility of CsBr in the organic solvent. Herein, we fabricate a CsPbBr3 film with a two-step solution method and realize the ASE under the long pulse pumping. Meanwhile, a CsBr aqueous solution is used as an effective additive to increase the concentration of Cs+ in the precursor solution and then to improve the optical amplification properties of the CsPbBr3 films. The films exhibit better crystalline and enhanced photoluminescence intensity. Both the ASE threshold and gain have been significantly improved. Furthermore, the optimized film shows a satisfying stability of ASE after being placed in the air for more than two months.

Structural modulation induced by cobalt-based ionic liquids for enhanced thermoelectric transport in PEDOT:PSS.

Abstract: Poly(3,4ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) has been intensively studied for its thermoelectric applications. Structural modulation to improve crystalline ordering, chain conformation and film morphology is a promising way to decouple the trade-off between conductivity and Seebeck coefficient and thus improve the thermoelectric power factor. Post treatment with ionic liquid ([CoCl2 ⋅ 6H2 O]:[ChCl]) bearing cobalt-containing anions resulted in a remarkable enhancement of the power factor to 76.8 μW m-1 K-2 . This IL combines the influence of a high-boiling polar organic solvent and diffusing ions. A high σ mainly resulted from the efficient removal of PSS chains, ordering of the structure and delocalization of bipoloran-dominant transport after conformational change. The increase in S was not due to dedoping of PEDOT chains, but rather the sharp feature of the density of states at the Fermi level induced by ion-exchange with unconventional anions.

Low-Threshold Amplified Spontaneous Emission from Air-Stable CsPbBr3 Perovskite Films Containing Trace Amounts of Polyethylene Oxide.

Abstract: Organic additives can enhance the amplified spontaneous emission (ASE) performance of inorganic cesium lead halide perovskites (CsPbBr3 ) but volatility, potential hygroscopicity and oxidative degradation of these additives jeopardizes the thermal stability and shelf-life of blended CsPbBr3 films. To address this problem, we have fabricated perovskite films in a two-step solution protocol involving as little added polyethylene oxide (PEO) as possible. These films exhibited enhanced crystallization, improved photoluminescence (PL) intensity and prolonged lifetimes. Their hierarchical morphology and surface passivation lowered the ASE threshold from 278 to 176 μЈ/cm2 under one-photon nanosecond laser excitation. The proportion of added PEO was 0.3 wt% and was subsequently almost fully removed, thereby reducing its adverse influence on the stability of resulting films under continuous pulsed laser excitation. Stable ASE spectra could be stimulated after storage in air for 10 months.

Metal-Organic Frameworks: Synthetic Methods and Potential Applications

Abstract: Metal-organic frameworks represent a porous class of materials that are build up from metal ions or oligonuclear metallic complexes and organic ligands. They can be considered as sub-class of coordination polymers and can be extended into one-dimension, two-dimensions, and three-dimensions. Depending on the size of the pores, MOFs are divided into nanoporous, mesoporous, and macroporous items. The latter two are usually amorphous. MOFs display high porosity, a large specific surface area, and high thermal stability due to the presence of coordination bonds. The pores can incorporate neutral molecules, such as solvent molecules, anions, and cations, depending on the overall charge of the MOF, gas molecules, and biomolecules. The structural diversity of the framework and the multifunctionality of the pores render this class of materials as candidates for a plethora of environmental and biomedical applications and also as catalysts, sensors, piezo/ferroelectric, thermoelectric, and magnetic materials. In the present review, the synthetic methods reported in the literature for preparing MOFs and their derived materials, and their potential applications in environment, energy, and biomedicine are discussed.

An effective approach to enhanced thermoelectric properties of PEDOT:PSS films by a DES post‐treatment

Abstract: As conventional organic solvents present inherent toxicity, deep eutectic solvents (DES) have been considered as excellent candidates due to their green characteristics. In this work, thermoelectric properties enhancement of PEDOT:PSS films is achieved by introducing DES as an additive and post‐treatment reagent. Direct addition and post‐treatment approaches lead to a maximum Seebeck coefficient of 29.1 μV K⁻¹and electrical conductivity of 620.6 S cm⁻¹, respectively. In addition, an optimal power factor is obtained by DES post‐treatment, reaching up to 24.08 μW m⁻¹K⁻², which is approximately four orders of magnitude higher than the pure PEDOT:PSS. Assuming a thermal conductivity of 0.17 W m⁻¹K⁻¹, the maximum ZT value is estimated to be 0.042 at 300 K. Further, atomic force microscopy and X‐ray photoelectron spectroscopy are performed and suggest that the remarkably enhanced electrical conductivity originates from the removal of the excess insulating PSS and the phase separation between the PEDOT and PSS chains. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 885–892

Organic Devices: Fabrication, Applications, and Challenges

Abstract: The low cost of organic starting materials and ease of their fabrication processes have propelled the development of various organic devices and have also generated a considerable research interest in the scientific community. These devices make use of organic materials in the form of dielectrics, conductive polymers, or small organic molecules deposited mainly on flexible substrates to bring about the advantages of stretchability and moldability. Focussed and dedicated R&D activities conducted in this field during the last few decades have led to the development of novel and efficient organic devices that hold tremendous promise of a highly optimistic future. This review provides an insight into the area of organic devices with a particular emphasis on organic light emitting diodes, organic field effect transistors, organic solar cells, and organic thermoelectric devices. It presents a comprehensive survey that includes important milestones, fabrication processes, and applications of these devices. New materials and processes that enabled the recent technological advancements have been highlighted and discussed for each device category. The current challenges of the field are also discussed with a glance at the future prospects and directions for this emerging field.