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Articles you may be interested inFabrication and characterization of ink jet processed organic thin film transistors with poly-4-vinylphenol gate dielectric J. Vac. Sci. Technol. A 28, 873 (2010); 10.1116/1.3358162High performance nanocomposite thin film transistors with bilayer carbon nanotube-polythiophene active channel by ink-jet printing

OSCs can be applied to various fields due to their many advantages, such as high performance, low cost, flexibility, and potential for modulation. Recently, the research on OSCs has been focused on materials with high-performance organic donors and acceptors (fullerene and nonfullerene) and device structure research, such as ternary structure and tandem structure. These studies have contributed to developing high-performance OSCs with excellent power conversion efficiency (PCE) over 14% in single cells and 17.3% in tandem structure cells. [1][2][3][4][5][6][7][8][9][10] OSCs are based on an active layer that has a bulk-heterojunction (BHJ) structure that consists of an organic donor and acceptor, and OSCs generate excitons within the range of their optical properties. Additionally, OSCs show photovoltaic properties via the process of charge disassociation and charge transport. [11,12] Due to the limitation of the optical properties of organic donors and acceptors, carrier mobility and carrier balance are critical factors that determine the performance of OSCs. [13][14][15][16] Therefore, photogenerated carriers that have been generated in a BHJ have the disadvantage of exhibiting a lower mobility compared with inorganic semiconductor-based solar cells because of the organic semiconductor's inherent properties, such as monomolecular recombination and bimolecular recombination. [17][18][19] Additionally, certain of these photogenerated carriers return to the ground state through monomolecular trap-assisted recombination, [20][21][22] interfacial recombination, [23][24][25] and surface trap-assisted recombination, [26] and the carriers subsequently weaken the device performance because the reduction of current and internal potential occurs via a nonradiative relaxation process. [27,28] Therefore, it is necessary to enhance the carrier transport properties to improve the performance of OSCs.Recent research has reported important device structure modifications to improve the carrier transport properties of OSCs. Specifically, the carrier mobility can be increased by introducing a buffer layer through enhancing carrier transport, and the device performance can be enhanced by reducing the recombination. Hybrid organic solar cells are made through a simple one-pot coating process with conjugated polyelectrolytes (CPEs), poly[9,9-bis(4′sulfonatobutyl)fluorenealt-thiophene-doped (PFT-D). The hybrid active layer incorporated with PFT-D shows vertical phase separation by selfassembled properties of PFT-D, which result from a molecular dipole between the conjugated backbone and the side chain. The hybrid activelayer with PFT-D shows that homogeneous morphology, surface potential properties, and hydrophobic surface properties favor for enhancing photovoltaic performance. These results are identified by contact angle characteristics, X-ray photoelectron spectroscopy (XPS) profiling, and X-ray diffraction (XRD), atomic force measurement (AFM), and electrostatic force measurement (EFM) analyses. With fullerene based hybrid active...

In this study, we fabricated conventional structured organic solar cells (OSCs) by introducing a hole extraction layer (HEL) that consisted of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) and conjugated polymer electrolyte (CPE) poly[9,9-bis(4'-sulfonatobutyl)fluorene-alt-thiophene] (PFT-D). PFT-D has a -SO functional group that acts as a conjugate base against the -SOH of PSS. In addition, the molecular dipole of PFT-D can screen the Coulombic attraction between PEDOT chains and PSS chains. By blending PEDOT:PSS and PFT-D, the acidity of the HEL solution and changes to the surface morphology and potential of the HEL film as a function of exposure time in air were reduced. As a result, the half-life of the OSC fabricated with blended HEL was five times better at room temperature and 40% humidity without encapsulation as compared to the pristine PEDOT:PSS-based device.

In this study, we synthesized three conjugated polymer electrolytes (CPEs) with different conjugation lengths to control their dipole moments by varying spacers. P-type CPEs (PFT-D, PFtT-D, and PFbT-D) were generated by the facile oxidation of n-type CPEs (PFT, PFtT, and PFbT) and introduced as the hole-transporting layers (HTLs) of organic solar cells (OSCs) and polymer light-emitting diodes (PLEDs). To identify the effect on electrode work function tunability by changing the molecular conformation and arrangement, we simulated density functional theory calculations of these molecules and performed ultraviolet photoelectron spectroscopy analysis for films of indium tin oxide/CPEs. Additionally, we fabricated OSCs and PLEDs using the CPEs as the HTLs. The stability and performance were enhanced in the optimized devices with PFtT-D CPE HTLs compared to those of PEDOT:PSS HTL-based devices.

We have studied the photocurrent decay under gate bias in organic thin-film transistor (OTFT) using inkjet printed α,ω-dihexylquarterthiophene layer. The OTFT shows high photocurrents under light illumination and very slow decay of photocurrents under positive gate voltage. This is due to the gate voltage-controlled trapping and detrapping of the electrons near the interface. With increasing exposure time, more electrons are trapped and thus make the photocurrent decay slower. It is found that there is a power-law dependence between light exposure time and decay time constant.

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We report the fabrication and flexibility of the TFTs based on poly-Si and a-IGZO on polyimide (PI). The performances of the TFTs do not degrade upon 10,000 times rolling with 2 mm radius for a-IGZO and 4 mm for poly-Si TFTs. It is found that there is no electrostatic damage for the TFT backplane on PI with a conducting backbone.