We investigated the reduction of current fluctuations in few-layer black phosphorus (BP) field-effect transistors resulting from Al2O3 passivation. In order to verify the effect of Al2O3 passivation on device characteristics, measurements and analyses were conducted on thermally annealed devices before and after the passivation. More specifically, static and low-frequency noise analyses were used in monitoring the charge transport characteristics in the devices. The carrier number fluctuation (CNF) model, which is related to the charge trapping/detrapping process near the interface between the channel and gate dielectric, was employed to describe the current fluctuation phenomena. Noise reduction due to the Al2O3 passivation was expressed in terms of the reduced interface trap density values D(it) and N(it), extracted from the subthreshold slope (SS) and the CNF model, respectively. The deviations between the interface trap density values extracted using the SS value and CNF model are elucidated in terms of the role of the Schottky barrier between the few-layer BP and metal contact. Furthermore, the preservation of the Al2O3-passivated few-layer BP flakes in ambient air for two months was confirmed by identical Raman spectra.

Organic thin-film transistors (OTFTs) have attracted considerable attention because of their potential applications in large-area, flexible, and printed electronics. To achieve OTFT devices with desirable properties, recent research has primarily focused on molecular design, [1,2] dielectric-semiconductor interfacial engineering, [3][4][5] and device optimization. [6][7][8][9][10][11] The use of conjugated polymer blends as active materials has brought a new way to tune and optimize the electronic properties of devices; for example, ambipolar field-effect charge transport has been reported in binary blends of p-and n-type conjugated polymers or oligomers. [12,13] Semiconducting and insulating polymer blends have also attracted increasing interest, because they can combine the electronic properties of semiconducting polymers with the low cost and excellent mechanical characteristics of insulating polymers. However, the presence of the insulating component tends to degrade the device performance by diluting the current density of the film. [14,15] To the best of our knowledge, the only effective approach to overcome this drawback is controlling the blended films to form vertically phase-separated structures, to keep the connectivity of the semiconducting layer in the presence of insulating components. In recent works, the composites with this structures have been used in OTFTs to fabricate low-voltage-driven devices, to improve environmental stability or reduce semiconductor cost. [16][17][18][19][20][21] However, the phase-separation process in polymer blends is very complicated. The final morphology in the blend films is highly sensitive to many factors, including the solvent evaporation rate, solubility parameters, film-substrate interactions, the surface tension of the components, and the film thickness. Vertical phase separation can only take place under extreme conditions. [22,23] Therefore, to develop a more facile and general method for realizing high-performance, low-semiconductor-cost devices is of great technological and academic significance.In this paper, we show that the percolation threshold of semiconducting/insulating polymer blends can be drastically decreased by depositing them from a marginal solvent with temperature-dependent solubility. Morphology and crystallinestructure studies reveal that the excellent electronic performance of the devices derives from the efficient charge transport and the good connectivity observed in highly crystalline, interconnected nanofibrillar networks of semiconductors embedded in an insulator matrix.Semiconductor/insulator-blend mother solutions were prepared by blending poly(3-hexylthiophene) (P3HT) and amorphous polystyrene (PS) in dichloromethane (CH 2 Cl 2 ), which is a marginal solvent for P3HT.[24] To completely dissolve P3HT, the CH 2 Cl 2 solution was kept at approximately 40 8C. For comparison, chloroform (CHCl 3 ), which is a good solvent for P3HT, was used as a reference. Thin films with different P3HT and PS ratios were fabricated on a silicon substrat...

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The effect of chemical-composition modification on the chiroptical property of chiral organic ammonium cation-containing organic inorganic hybrid perovskite (chiral OIHP) is investigated. Varying the mixing ratio of bromide and iodide anions in Sor R-C 6 H 5 CH 2 (CH 3 )NH 3 ) 2 PbI 4(1−x) Br 4x modifies the band gap of chiral OIHP, leading to a shift of the circular dichroism (CD) signal from 495 to 474 nm. However, it is also found that an abrupt crystalline structure transition occurs, and the CD signal is turned off when iodide-determinant phases are transformed into the bromide-determinant phase. To obtain CD in the wavelength range where the bromide-determinant phase is supposed to exhibit chiroptical activity, that is, <474 nm, Sor R-C 12 H 7 CH 2 (CH 3 )NH 3 with a larger spacer group can be adopted; thus, the CD signal can be further blue-shifted to ∼375 nm. Here, we show that chemical-composition modification of chiral OIHP affects the chiroptical properties of chiral OIHP in two ways: (1) tuning the wavelength of CD by modulating the excitonic band structure and (2) switching the CD on and off by inducing a crystalline-structure change. These properties can be utilized for structural engineering of high-performance chiroptical materials for spin-polarized light-emitting devices and polarization-based optoelectronics.