ファンデルワールス材料薄膜における熱電特性

早大学位記番号:新8490早稲田大

Formation of environmentally stable hole-doped graphene films with instantaneous and high-density carrier doping via a boron-based oxidant

Large-area graphene films have substantial potential for use as next-generation electrodes because of their good chemical stability, high flexibility, excellent carrier mobility, and lightweight structure. However, various issues remain unsolved. In particular, high-density carrier doping within a short time by a simple method, and air stability of doped graphene films, are highly desirable. Here, we demonstrate a solution-based high-density (>1014 cm−2) hole doping approach that promises to push the performance limit of graphene films. The reaction of graphene films with a tetrakis(pentafluorophenyl)borate salt, containing a two-coordinate boron cation, achieves doping within an extremely short time (4 s), and the doped graphene films are air stable for at least 31 days. X-ray photoelectron spectroscopy reveals that the graphene films are covered by the chemically stable anions, resulting in an improved stability in air. Moreover, the doping reduces the transmittance by only 0.44 ± 0.23%. The simplicity of the doping process offers a viable route to the large-scale production of functional graphene electrodes

Charge and thermoelectric transport mechanism in donor-acceptor copolymer films

Wearable thermoelectric conversion devices are one of the key technologies for future sustainable society, and flexible conducting polymer films are strong candidates for these applications. However, the thermoelectric transport mechanism of these materials is still unclear due to their unique disordered nature, in particular the poor interconnectivity between crystalline domains. Here, to overcome this limit, donor-acceptor (D-A) copolymer films are selected because of the efficient connection between domains via rigid tie molecules. We investigated their thermoelectric and carrier transport properties using the electrolyte-gating technique and perfectly described both of them based on the two-dimensional variable range hopping model with a linear density of states around the Fermi level energy. The present results provide a fundamental understanding of the thermoelectric physics in D-A copolymer films towards application in wearable devices.11Yscopu

Triethylene Glycol Substituted Diketopyrrolopyrrole- and Isoindigo-Dye Based Donor–Acceptor Copolymers for Organic Light-Emitting Electrochemical Cells and Transistors

Triethylene glycol, a common side chain, is attached to two different dye moieties, diketopyrrolopyrrole (DPP) and isoindigo (II), and their bromo derivative monomers are copolymerized, respectively, with common bisstannyl alkylated bithiophene via Stille coupling. The resulting donor–acceptor low-bandgap copolymers, namely, PTDPP-DT and PTII-DT, are rationally deigned and synthesized conjugated polymeric systems suitable for doping. Both polymers are successfully investigated as single-component and composite-system-based electrochemical transistors and light-emitting electrochemical cells. A PTDPP-DT thin film exhibits relatively high electrical conductivity of up to 80 S cm−1 in the electrochemically doped state, whereas PTII-DT thin film prevents the macroscopic charge transport due to a large-scale crystalline disorientation. Upon evaluating both polymers as active conjugated materials in light-emitting electrochemical cells, they both exhibit emission under efficient electron/hole doping conditions.</p

Triethylene Glycol Substituted Diketopyrrolopyrrole‐ and Isoindigo‐Dye Based Donor–Acceptor Copolymers for Organic Light‐Emitting Electrochemical Cells and Transistors

Triethylene glycol, a common side chain, is attached to two different dye moieties, diketopyrrolopyrrole (DPP) and isoindigo (II), and their bromo derivative monomers are copolymerized, respectively, with common bisstannyl alkylated bithiophene via Stille coupling. The resulting donor–acceptor low-bandgap copolymers, namely, PTDPP-DT and PTII-DT, are rationally deigned and synthesized conjugated polymeric systems suitable for doping. Both polymers are successfully investigated as single-component and composite-system-based electrochemical transistors and light-emitting electrochemical cells. A PTDPP-DT thin film exhibits relatively high electrical conductivity of up to 80 S cm−1 in the electrochemically doped state, whereas PTII-DT thin film prevents the macroscopic charge transport due to a large-scale crystalline disorientation. Upon evaluating both polymers as active conjugated materials in light-emitting electrochemical cells, they both exhibit emission under efficient electron/hole doping conditions.</p

Highly Efficient and Stable Perovskite Solar Cells by Interfacial Engineering Using Solution-Processed Polymer Layer

Solution-processed organo-lead halide perovskite solar cells with deep pinholes in the perovskite layer lead to shunt-current leakage in devices. Herein, we report a facile method for improving the performance of perovskite solar cells by inserting a solution-processed polymer layer between the perovskite layer and the hole-transporting layer. The photovoltaic conversion efficiency of the perovskite solar cell increased to 18.1% and the stability decreased by only about 5% during 20 days of exposure in moisture ambient conditions through the incorporation of a poly­(methyl methacrylate) (PMMA) polymer layer. The improved photovoltaic performance of devices with a PMMA layer is attributed to the reduction of carrier recombination loss from pinholes, boundaries, and surface states of perovskite layer. The significant gain generated by this simple procedure supports the use of this strategy in further applications of thin-film optoelectronic devices