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An experimental and theoretical study of the structural ordering of the PTB7 polymer at a mesoscopic scale
摘要： Our extensive study based on optoelectronic and electric measurements (which consisted of: UV-Vis absorption, photoluminescence, surface photovoltage measurement, charge extraction by linearly increasing voltage, and energy-resolved electrochemical impedance spectroscopy) revealed the fundamental role of the thickness of the formation of intra- and interchain interaction in poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7) films. We have shown that the final optoelectronic and electronic properties of PTB7 films are governed by the structural ordering development of the transition from nano- to submicroscale. The ordering of polymer chains and competition between the formation of J- and H-aggregates results in a non-trivial dependence of luminescence, exciton diffusion length, transport band gap, and defect concentration. According to a theoretical analysis, the driving forces responsible for the observed phenomena are associated with the thickness threshold dependence of the thin film drying mode which can proceed with or without the polymer skin formation on the surface of forming film.
关键词： low band-gap,thickness dependences,Conjugated polymers
更新于2025-10-22 19:40:53
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Buchwald-Hartwig Coupling at the Naphthalenediimide Core: Access to Dendritic, Panchromatic NIR Absorbers with Exceptionally Low Band Gap
摘要： The ?rst successful Buchwald?Hartwig reaction at the naphthalenediimide core is reported, leading to the coupling of diverse secondary aromatic amines including dendritic donors. The G1-dendrimer-based donor exhibit blackish color, providing access to black absorbing systems. λ onset values up to 1070 nm was achieved, which is the maximum from a single NDI sca?old. These dyes also manifest multielectron reservoir properties. A total of eight-redox states with a band gap of ～0.95 eV was accomplished.
关键词： dendritic donors,low band gap,black absorbing systems,Buchwald?Hartwig reaction,naphthalenediimide,multielectron reservoir properties,NIR absorbers
更新于2025-09-23 15:21:21
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Synthesis and Photovoltaic Effect of Electron-Withdrawing Units for Low Band Gap Conjugated Polymers Bearing Bi(thienylenevinylene) Side Chains
摘要： A novel (E)-5-(2-(5-alkylthiothiophen-2-yl)vinyl)thien-2-yl (TVT)-comprising benzo[1,2-b:4,5-b’]dithiophene (BDT) derivative (BDT-TVT) was designed and synthetized to compose two donor-acceptor (D-A) typed copolymers (PBDT-TVT-ID and PBDT-TVT-DTNT) with the electron-withdrawing unit isoindigo (ID) and naphtho[1,2-c:5,6-c’]bis[1,2,5]thiadiazole (NT), respectively. PBDT-TVT-ID and PBDT-TVT-DTNT showed good thermal stability (360 °C), an absorption spectrum from 300 nm to 760 nm and a relatively low lying energy level of Highest Occupied Molecular Orbital (EHOMO) (?5.36 to –5.45 eV), which could obtain a large open-circuit voltage (Voc) from photovoltaic devices with PBDT-TVT-ID or PBDT-TVT-DTNT. The photovoltaic devices with ITO/PFN/polymers: PC71BM/MoO3/Ag structure were assembled and exhibited a good photovoltaic performance with a power conversion efficiency (PCE) of 4.09% (PBDT-TVT-ID) and 5.44% (PBDT-TVT-DTNT), respectively. The best PCE of a PBDT-TVT-DTNT/PC71BM-based device mainly originated from its wider absorption, higher hole mobility and favorable photoactive layer morphology.
关键词： polymer solar cells,photovoltaic property,benzo[1,2-b:4,5-b’]dithiophene,low band gap,bi(thienylenevinylene)
更新于2025-09-11 14:15:04
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Structural, morphological, optical and dielectric properties of M <sup>3+</sup> /PVA/PEG SPE Films (M = La, Y, Fe or Ir)
摘要： Low band gap polymer complexes are promising due to its flexibility, and exhibiting electronic and optical properties of inorganic semiconductors. The effect of PEG on the physical properties of PVA was evaluated. Then, blend (PVA: PEG = 50:50) doped with rare earth (La or Y) and transition metal (Fe or Ir) chlorides to obtain solid polymer electrolyte films. XRD shows that adding PEG to PVA results in a new peak, 2θ = 23o with increased intensity as PEG ratio increases. However, doping with La3+, Fe3+ or Ir3+ eliminate this peak and decrease the crystallinity. SEM exhibits significant changes in the morphology of films. FTIR confirms miscibility between PVA & PEG and the complexation of the salts. The optical band gap (Eg) of PVA ~ 5.37 eV, decreased slightly by blending with PEG. While it decreased significantly to 2.64 eV and 2.78 eV after doping with Fe3+ or Ir3+. There are a consistency between Eg values obtained by Tauc's model and that obtained from the optical dielectric loss. The dielectric constant and loss, in temperature range 303–405 K & frequency range 1.0 kHz ‐ 5.0 MHz, indicate one or two relaxation peak(s) depending on the film composition. Accordingly, conduction mechanism varied between correlated barrier hopping and large polaron tunneling. The DC conductivity was strongly depend on the dielectric loss. The transition metal salts appear to be more effective than the rare earth ones in increasing σac of films to higher values that candidates them in semiconductors industry.
关键词： conduction mechanism,low band gap polymers,activation energy,PVA/PEG blend,rare earth metal complexation,solid polymer electrolyte
更新于2025-09-09 09:28:46
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Charge Carrier Polarity Modulation in Diketopyrrolopyrrole–Based Low Band Gap Semiconductors by Terminal Functionalization
摘要： Organic semiconductors with variable charge carrier polarity are required for optoelectronic applications. Herein, we report the synthesis of three novel diketopyrrolopyrrole (DPP) based D–A molecules having three different terminal groups (amide, ester and dicyano) and studied their electronic properties. Increase in electron acceptor strength from amide to dicyano, leads to a bathochromic shift in absorption. Photoconductivity and field–effect transistor (FET) measurements confirmed that a small increase in acceptor strength can results in a large change in the charge transport properties from p–type to n–type. The molecule with amide group, DPP–Amide, exhibited a moderate p–type mobility (1.3 × 10–2 cm2V?1s?1), whereas good n–type mobilities were observed for molecules with an ester moiety, DPP–Ester (1.5 × 10–2 cm2V?1s?1) and with a dicyano group, DPP–DCV (1 × 10–2 cm2V?1s?1). The terminal functional group modification approach presented here is a simple and efficient method to alter the charge carrier polarity of organic semiconductors.
关键词： FP-TRMC,self-assembly,p-n switch,low band gap,Diketopyrrolopyrrole
更新于2025-09-04 15:30:14
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[Smart Innovation, Systems and Technologies] Information and Communication Technology for Intelligent Systems Volume 107 (Proceedings of ICTIS 2018, Volume 2) || Performance Booster Electrical Drain SiGe Nanowire TFET (EDD-SiGe-NW-TFET) with DC Analysis and Optimization
摘要： In this paper, new concept for TFET nanowire is proposed to eliminate the issues aroused in MOSFET due to continuous scaling the device dimensions. Proposed device uses the concept of electrically doping as well as physically doping. Other than that low band gap material, silicon germanium (SiGe), is used at source region and high k dielectric is used at source–channel interface to improve the performance of the proposed structure. Simulation is done using 3D TCAD ATLAS simulator, and result validates that the proposed device is suitable for low power application. Furthermore, simulation is done for the different diameters and channel lengths for optimization.
关键词： Electrical drain,Nanowire TFET,Low band gap,Hetero dielectric
更新于2025-09-04 15:30:14